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Cited by 125Mitochondrial Function and PathologyAlzheimer's disease research and treatmentsAutophagy in Disease and Therapy

Altered mitochondrial dynamics and function in APOE4-expressing astrocytes

Open access
Schmukler, Eran, Solomon, Shira, Simonovitch, Shira, Goldshmit, Yona, Wolfson, Eya, Michaelson, Daniel Morris, Pinkas-Kramarski, Ronit·2020·Cell Death & Disease
DOI 10.1038/s41419-020-02776-4PMC PMC7382473
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Abstract

APOE4 is a major risk factor for sporadic Alzheimer’s disease; however, it is unclear how it exerts its pathological effects. Others and we have previously shown that autophagy is impaired in APOE4 compared to APOE3 astrocytes, and demonstrated differences in the expression of mitochondrial dynamics proteins in brains of APOE3 and APOE4 transgenic mice. Here, we investigated the effect of APOE4 expression on several aspects of mitochondrial function and network dynamics, including fusion, fission, and mitophagy, specifically in astrocytes. We found that APOE3 and APOE4 astrocytes differ in their mitochondrial dynamics, suggesting that the mitochondria of APOE4 astrocytes exhibit reduced fission and mitophagy. APOE4 astrocytes also show impaired mitochondrial function. Importantly, the autophagy inducer rapamycin enhanced mitophagy and improved mitochondrial functioning in APOE4 astrocytes. Collectively, the results demonstrate that APOE4 expression is associated with altered mitochondrial dynamics, which might lead to impaired mitochondrial function in astrocytes. This, in turn, may contribute to the pathological effects of APOE4 in Alzheimer’s disease.

AI snapshot

Written from the paper’s full text.

TL;DR

APOE4-expressing astrocytes show altered mitochondrial dynamics—reduced fission and parkin-mediated mitophagy—and impaired mitochondrial function compared with APOE3 astrocytes. Rapamycin-induced mitophagy improved mitochondrial function in APOE4 astrocytes, suggesting a possible rescue pathway.

Key findings

  • APOE4 astrocytes had lower Drp1 (fission), higher Mfn1 (fusion), and increased parkin levels; they also showed a reduced LC3-II/LC3-I ratio, indicating decreased autophagy. Similar mitochondrial-dynamics protein changes were detected in primary APOE4 mouse astrocytes and in GFAP-positive astrocytes in APOE3/APOE4 mouse brain sections.
  • Mitochondrial networks in APOE4 astrocytes were more hyperfused, with more branching and fewer individual mitochondria (n ≥ 50 cells).
  • After CCCP-induced mitochondrial damage, mitophagy was impaired in APOE4 astrocytes: ~90% of autophagosomes in APOE3 astrocytes were fused with lysosomes versus ~55% in APOE4 astrocytes; EM showed APOE4 astrocytes formed autophagosomes that did not contain mitochondria.
  • APOE4 astrocytes showed impaired mitochondrial function, including lower MMP-sensitive MitoTracker Red fluorescence, higher full-length PINK1 and lower cleaved PINK1, reduced MTT metabolism, less dense cristae, lower medium pH, and reduced ATP levels. Rapamycin (150 nM) enhanced mitophagy and restored mitochondrial metabolism, augmented MMP, and corrected medium pH in APOE4 astrocytes.

Methods

  • Human APOE3/APOE4 targeted-replacement astrocyte cell lines, mouse primary astrocytes, and brain sections from APOE3/APOE4 targeted-replacement mice were used.
  • Analyses included immunoblot, immunoprecipitation, mitochondrial fractionation, qRT-PCR, confocal microscopy with MitoTracker/Mito-GFP and MiNa morphology analysis, electron microscopy, MTT and CellTiter-Glo assays, flow cytometry for MMP/mitochondrial mass, and medium pH measurement.
  • Experiments were performed at least 3 times; differences were tested with one-sided Student’s t test, with p < 0.05 considered significant.

Limitations

  • The paper states that the mechanism by which APOE4 affects mitochondrial dynamics is yet to be investigated; it may involve direct apoE4 interaction with mitochondria or indirect effects through autophagy/lysosomal machinery.
  • Evident from the text: most mechanistic work uses immortalized APOE3/APOE4 astrocyte cell lines and mouse primary astrocytes, with limited in vivo functional rescue data; rapamycin restoration was shown in cultured astrocytes, not in mice or human tissue.
  • Evident from the text: some findings were context-dependent, e.g., Drp1 differences in primary astrocytes were detected only in 12-week cultures, and the hyperfused APOE4 network was not accompanied by greater mitochondrial mass, suggesting a static hyperfused state rather than increased biogenesis.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/s41419-020-02776-4

Cites

53 of 53 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

69 of 85 cited sources checked · 33 supported · 0 flagged · accuracy not yet measured

  • Interpretationown data

    APOE4 astrocytes have decreased autophagy.

    “indicating decreased autophagy30”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [30] Klionsky, D. J. et al. Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy 12, 1–222 (2016). source

      The selective-autophagy section (p. 141) mentions astrocytes degrading axon-derived mitochondria, but does not discuss APOE4 or reduced autophagy in APOE4 astrocytes. Searches for APOE4, apolipoprotein E, and astrocytes found no passage in our copy that addresses the claimed decrease; the copy is also marked as truncated. (LLM, conf=0.70)

      Experimental — accuracy not yet measured
  • Premisecitation

    APOE4 is associated with impaired autophagy in astrocytes.

    “Previously, others and we have found that APOE4 is associated with impaired autophagy in astrocytes13,14, which is linked to reduced clearance of Aβ plaques and protein aggregates13,14.”
    • Also stated in: § Abstract · boosted
      “Others and we have previously shown that autophagy is impaired in APOE4 compared to APOE3 astrocytes”
    • Also stated in: § Discussion · plain
      “APOE4 is associated with impaired autophagy in astrocytes13,14”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [13] Simonovitch, S. et al. Impaired autophagy in APOE4 astrocytes. J. Alzheimers Dis. 51, 915–927 (2016). source
    • cites [14] Parcon, P. A., et al. Apolipoprotein E4 inhibits autophagy gene products through direct, specific binding to CLEAR motifs. Alzheimer’s Demen. https://doi.org/10.1016/j.jalz.2017.07.754 (2017). source
  • Premisecitation

    Differences in expression of mitochondrial dynamics proteins exist in APOE4 transgenic mouse brains.

    “Also, our recent findings revealed differences in the expression of mitochondrial dynamics proteins in APOE4 transgenic mouse brains15.”
    • Also stated in: § Abstract · boosted
      “demonstrated differences in the expression of mitochondrial dynamics proteins in brains of APOE3 and APOE4 transgenic mice”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [15] Simonovitch, S., Schmukler, E., Masliah, E., Pinkas-Kramarski, R. & Michaelson, D. M. The effects of APOE4 on mitochondrial dynamics and proteins in vivo. J. Alzheimers Dis. 70, 861–875 (2019). source
  • Findingown data

    APOE4 astrocytes exhibit increased parkin levels.

    “increased parkin levels (targets mitochondria for mitophagy, followed by proteasomal/lysosomal degradation26–29)”
    Quote in the paperSubstantial claim4 of 4 sources checked
    • cites [26] Vives-Bauza, C. et al. PINK1-dependent recruitment of Parkin to mitochondria in mitophagy. Proc. Natl Acad. Sci. USA 107, 378–383 (2010). source

      The paper’s discussion of the findings (indexed as Abstract; page unavailable) reports PINK1-dependent recruitment of Parkin to mitochondria and proposes that damaged mitochondria are delivered to perinuclear lysosomes for autophagic degradation. It does not support the parenthetical’s additional reference to proteasomal degradation. The citation is attached to that mechanistic explanation, not to the citing authors’ observation of increased Parkin levels in APOE4 astrocytes. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [27] Narendra, D., Tanaka, A., Suen, D. F. & Youle, R. J. Parkin is recruited selectively to impaired mitochondria and promotes their autophagy. J. Cell Biol. 183, 795–803 (2008). source

      The citation is attached to the parenthetical mechanism, not the observation of increased Parkin levels in APOE4 astrocytes. The Results and discussion (page unavailable) show that Parkin is recruited to impaired mitochondria and promotes their autophagic, lysosome-dependent removal, but do not establish the claimed proteasomal degradation step. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [28] Seirafi, M., Kozlov, G. & Gehring, K. Parkin structure and function. FEBS J. 282, 2076–2088 (2015). source
    • cites [29] Rakovic, A. et al. Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1)-dependent ubiquitination of endogenous Parkin attenuates mitophagy: study in human primary fibroblasts and induced pluripotent stem cell-derived neurons. J. Biol. Chem. 288, 2223–2237 (2013). source
    • Rests on an assumption: The human APOE3 and APOE4 targeted-replacement astrocyte cell lines differ only in APOE genotype.
  • Premisecitation

    Mitochondrial dysfunction represents an early event in AD.

    “Mitochondrial dysfunction plays a fundamental role in AD pathogenesis2 and represents an early event2.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [2] Swerdlow, R. H. Mitochondria and mitochondrial cascades in Alzheimer’s disease. J. Alzheimer’s Dis.: JAD 62, 1403–1416 (2018). source

      The Conclusions state that mitochondrial and bioenergetic changes seem to precede detectable changes in Aβ homeostasis, supporting an early role in AD. But the paper also says both primary and secondary mitochondrial cascades are possible, so it does not establish mitochondrial dysfunction as an early event in all AD cases. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
  • Classified as probably not a substantial claim. 29
  • May combine two claims. 39
  • The quote only partly states this claim. 1

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Several pathways mediate mitophagy, including the PINK1/parkin pathway.

    “Several pathways mediate mitophagy, including the PINK1/parkin pathway5,8.”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [5] Pickles, S., Vigie, P. & Youle, R. J. Mitophagy and quality control mechanisms in mitochondrial maintenance. Curr. Biol. 28, R170–R185 (2018). source
    • cites [8] Truban, D., Hou, X., Caulfield, T. R., Fiesel, F. C. & Springer, W. PINK1, parkin, and mitochondrial quality control: what can we learn about Parkinson’s disease pathobiology? J. Parkinson’s Dis. 7, 13–29 (2017). source

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    During mitophagy, Mfn1 undergoes ubiquitination by parkin followed by proteasomal degradation, which suppresses mitochondrial fusion and allows removal of mitochondria from the network.

    “During mitophagy, Mfn1 undergoes ubiquitination by parkin followed by proteasomal degradation, which suppresses mitochondrial fusion and allows the removal of mitochondria from the network8.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [8] Truban, D., Hou, X., Caulfield, T. R., Fiesel, F. C. & Springer, W. PINK1, parkin, and mitochondrial quality control: what can we learn about Parkinson’s disease pathobiology? J. Parkinson’s Dis. 7, 13–29 (2017). source

  • May combine two claims.

    Findingown data

    Levels of Tom40 and Tom20 are higher in APOE4 astrocytes.

    “the levels of two other mitochondrial parkin substrates, namely Tom40 and Tom2035, exhibited higher levels in APOE4 astrocytes (Fig. S2d).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [35] Yoshii, S. R., Kishi, C., Ishihara, N. & Mizushima, N. Parkin mediates proteasome-dependent protein degradation and rupture of the outer mitochondrial membrane. J. Biol. Chem. 286, 19630–19640 (2011). source

  • Classified as probably not a substantial claim.

    Premisecitation

    Several studies demonstrated a link between APOE4 and mitochondrial dysfunction, mainly in neurons.

    “Several studies demonstrated a link between APOE4 and mitochondrial dysfunction, mainly in neurons9–11; yet the effect of APOE4 on mitochondrial dynamics was less studied.”
    Quote in the paperSubstantial claim3 of 3 sources checked
    • cites [9] Dose, J., Huebbe, P., Nebel, A. & Rimbach, G. APOE genotype and stress response—a mini review. Lipids Health Dis. 15, 121 (2016). source
    • cites [10] Nakamura, T., Watanabe, A., Fujino, T., Hosono, T. & Michikawa, M. Apolipoprotein E4 (1-272) fragment is associated with mitochondrial proteins and affects mitochondrial function in neuronal cells. Mol. Neurodegeneration 4, 35 (2009). source
    • cites [11] Chen, H. K. et al. Apolipoprotein E4 domain interaction mediates detrimental effects on mitochondria and is a potential therapeutic target for Alzheimer disease. J. Biol. Chem. 286, 5215–5221 (2011). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Damaged mitochondria are degraded by selective autophagy, termed mitophagy, following fission.

    “Damaged mitochondria are degraded by selective autophagy, termed mitophagy, following fission5.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [5] Pickles, S., Vigie, P. & Youle, R. J. Mitophagy and quality control mechanisms in mitochondrial maintenance. Curr. Biol. 28, R170–R185 (2018). source

      The Introduction (page not provided) defines mitophagy as selective autophagic elimination of mitochondria, and the Mitophagy in mammals section includes mitochondrial damage as a trigger. But the Quality control at the sub-organelle level section describes fission and autophagosome formation as coupled and says loss of Drp1 delays, but does not abolish, mitophagy. It does not support presenting fission as a step that always precedes degradation. (LLM, conf=0.85)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Several proteins are required for mitochondrial fusion, including the mitofusins (Mfn1/Mfn2).

    “Several proteins are required for mitochondrial fusion, including the mitofusins (Mfn1/Mfn2)3,4.”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [3] Eisner, V., Picard, M. & Hajnoczky, G. Mitochondrial dynamics in adaptive and maladaptive cellular stress responses. Nat. Cell Biol. 20, 755–765 (2018). source
    • cites [4] Tilokani, L., Nagashima, S., Paupe, V. & Prudent, J. Mitochondrial dynamics: overview of molecular mechanisms. Essays Biochem. 62, 341–360 (2018). source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    PINK1 is stabilized on the OMM leading to recruitment and activation of parkin, which ubiquitinates several mitochondrial proteins leading to mitophagy.

    “The mitochondrial kinase PINK1 is stabilized on the OMM leading to the recruitment and activation of parkin (E3 ubiquitin ligase), which ubiquitinates several mitochondrial proteins leading to mitophagy5,8.”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [5] Pickles, S., Vigie, P. & Youle, R. J. Mitophagy and quality control mechanisms in mitochondrial maintenance. Curr. Biol. 28, R170–R185 (2018). source
    • cites [8] Truban, D., Hou, X., Caulfield, T. R., Fiesel, F. C. & Springer, W. PINK1, parkin, and mitochondrial quality control: what can we learn about Parkinson’s disease pathobiology? J. Parkinson’s Dis. 7, 13–29 (2017). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Mitochondrial fusion is enhanced under stress and high energetic demands, allowing increased bioenergetic efficiency.

    “Mitochondrial fusion is enhanced under stress and high energetic demands, allowing increased bioenergetic efficiency7.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [7] Westermann, B. Bioenergetic role of mitochondrial fusion and fission. Biochim. Biophys. Acta 1817, 1833–1838 (2012). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Proteasomal degradation of parkin occurs during mitophagy due to autoubiquitination, halting its activity.

    “Proteasomal degradation of parkin was demonstrated during mitophagy due to autoubiquitination, halting its activity28,29,33,34.”
    Quote in the paperNot a substantial claim4 of 4 sources checked
    • cites [28] Seirafi, M., Kozlov, G. & Gehring, K. Parkin structure and function. FEBS J. 282, 2076–2088 (2015). source

      The section ‘Parkin is an RBR E3 ubiquitin ligase’ (page unavailable) says parkin becomes ubiquitinated and that this may play a role in its own degradation during the mitophagy pathway. It does not establish that parkin is degraded by the proteasome, that autoubiquitination causes that degradation, or that degradation halts its activity. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [29] Rakovic, A. et al. Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1)-dependent ubiquitination of endogenous Parkin attenuates mitophagy: study in human primary fibroblasts and induced pluripotent stem cell-derived neurons. J. Biol. Chem. 288, 2223–2237 (2013). source

      The Discussion (page not provided) says endogenous Parkin becomes self-ubiquitinated during mitochondrial depolarization and is likely degraded through the ubiquitin–proteasome system. It proposes that this reduces the Parkin available to translocate to mitochondria, attenuating further mitophagy; it does not demonstrate that Parkin’s activity halts. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites [33] Chaugule, V. K. et al. Autoregulation of Parkin activity through its ubiquitin-like domain. EMBO J. 30, 2853–2867 (2011). source

      The Discussion (page unavailable) describes proteasomal degradation of Parkin mutants and proposes that autoubiquitination may lead to Parkin degradation and inactivation. It does not demonstrate that this occurs during mitophagy; it instead suggests that autoubiquitination and degradation of wild-type Parkin are absent or prevented in normal cellular conditions. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [34] Byrd, R. A. & Weissman, A. M. Compact Parkin only: insights into the structure of an autoinhibited ubiquitin ligase. EMBO J. 32, 2087–2089 (2013). source

      The Abstract says activating Parkin mutations may lead to increased autoubiquitination and degradation. It separately says Parkin promotes proteasomal degradation of mitochondrial proteins and mitophagy. It does not demonstrate that Parkin itself is proteasomally degraded during mitophagy or that this halts its activity. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    During mitochondrial fission, cytosolic Drp1 is recruited to mitochondrial receptors (e.g., Fis1), allowing mitochondrial partitioning, turnover and reduction of network size under low energetic demand.

    “During mitochondrial fission, cytosolic Drp1 is recruited to mitochondrial receptors (e.g., Fis1)3,4, allowing mitochondrial partitioning, turnover and reduction of network size under low energetic demand4,7.”
    Quote in the paperNot a substantial claim3 of 3 sources checked
    • cites [3] Eisner, V., Picard, M. & Hajnoczky, G. Mitochondrial dynamics in adaptive and maladaptive cellular stress responses. Nat. Cell Biol. 20, 755–765 (2018). source

      The “Mitochondrial fusion and fission dynamics” section (page unavailable) describes cytoplasmic DRP1 recruitment for division and says fission enables segregation of damaged mitochondria for mitophagy. It names MFF and MID49/51, not Fis1, in the recruitment mechanism. It also does not establish that low energetic demand drives network reduction; its discussion of glucose starvation instead describes inhibited fission and hyperfusion. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [4] Tilokani, L., Nagashima, S., Paupe, V. & Prudent, J. Mitochondrial dynamics: overview of molecular mechanisms. Essays Biochem. 62, 341–360 (2018). source

      The “Drp1 and adaptors” section says that mainly cytosolic Drp1 is recruited to mitochondria for fission, and Figure 4 describes division into two daughter mitochondria. But it identifies MFF and MiD49/51—not Fis1—as the relevant Drp1 receptors in mammals under basal conditions. The Introduction links fragmentation to quality control, but the copy does not establish that fission reduces network size specifically under low energetic demand. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites [7] Westermann, B. Bioenergetic role of mitochondrial fusion and fission. Biochim. Biophys. Acta 1817, 1833–1838 (2012). source

      The Introduction says Drp1 assembles on the mitochondrial surface to mediate fission, and section 4 describes partitioning during cell division and the removal of damaged mitochondria after fission. Sections 2 and 6 associate fragmented mitochondria with resting or respiratory-inactive cells. Our copy does not establish recruitment of cytosolic Drp1 by Fis1 or say that fission reduces network size specifically in response to low energetic demand. Page numbers are unavailable in our copy. (LLM, conf=0.87)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim.

    Premisecitation

    Mitochondrial dynamics are abnormal in AD brains.

    “Mitochondrial dynamics were shown to be abnormal in AD brains6.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [6] Zhu, X., Perry, G., Smith, M. A. & Wang, X. Abnormal mitochondrial dynamics in the pathogenesis of Alzheimer’s disease. J. Alzheimer’s Dis. 33, S253–262 (2013). source

  • Classified as probably not a substantial claim.

    Premisecitation

    Mitochondrial dysfunction plays a fundamental role in AD pathogenesis.

    “Mitochondrial dysfunction plays a fundamental role in AD pathogenesis2 and represents an early event2.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [2] Swerdlow, R. H. Mitochondria and mitochondrial cascades in Alzheimer’s disease. J. Alzheimer’s Dis.: JAD 62, 1403–1416 (2018). source

      The Introduction says mitochondrial dysfunction may play an important, relatively upstream role in AD, and the Conclusions say mitochondrial and bioenergetic changes seem to precede detectable changes in Aβ homeostasis. The source supports a significant and potentially early role, but presents both points as possibilities rather than established facts. (LLM, conf=0.85)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Impaired autophagy in APOE4 astrocytes is linked to reduced clearance of Aβ plaques and protein aggregates.

    “Previously, others and we have found that APOE4 is associated with impaired autophagy in astrocytes13,14, which is linked to reduced clearance of Aβ plaques and protein aggregates13,14.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [13] Simonovitch, S. et al. Impaired autophagy in APOE4 astrocytes. J. Alzheimers Dis. 51, 915–927 (2016). source
    • cites [14] Parcon, P. A., et al. Apolipoprotein E4 inhibits autophagy gene products through direct, specific binding to CLEAR motifs. Alzheimer’s Demen. https://doi.org/10.1016/j.jalz.2017.07.754 (2017). source

  • May combine two claims.

    Premisecitation

    PINK1 accumulates on the OMM following MMP reduction, while it undergoes cleavage in healthy mitochondria due to proteasomal degradation.

    “PINK1, which accumulates on the OMM following MMP reduction, while it undergoes cleavage in healthy mitochondria due to proteasomal degradation5,8.”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [5] Pickles, S., Vigie, P. & Youle, R. J. Mitophagy and quality control mechanisms in mitochondrial maintenance. Curr. Biol. 28, R170–R185 (2018). source

      The Parkin and PINK1-dependent mitophagy section (page unavailable) says PINK1 is stabilized on the outer mitochondrial membrane when mitochondrial import is compromised, and that under basal conditions it is cleaved. It does not say proteasomal degradation causes cleavage: MPP and PARL cleave PINK1, after which the proteasome degrades the cleavage product. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [8] Truban, D., Hou, X., Caulfield, T. R., Fiesel, F. C. & Springer, W. PINK1, parkin, and mitochondrial quality control: what can we learn about Parkinson’s disease pathobiology? J. Parkinson’s Dis. 7, 13–29 (2017). source

      In “The Life Cycle of PINK1 – A Sensor for Mitochondrial Damage,” the paper says mitochondrial depolarization prevents import and full-length PINK1 accumulates on the OMM. It also says PINK1 is cleaved in healthy mitochondria, but cleavage is performed by mitochondrial proteases MPP and PARL; proteasomal degradation occurs afterward, rather than causing the cleavage. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Mitochondrial fusion is triggered by increased MMP and involves oligomerization of mitofusins on the OMM.

    “This process is triggered by increased mitochondrial membrane potential (MMP) and involves the oligomerization of mitofusins on the outer mitochondrial membrane (OMM)4.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [4] Tilokani, L., Nagashima, S., Paupe, V. & Prudent, J. Mitochondrial dynamics: overview of molecular mechanisms. Essays Biochem. 62, 341–360 (2018). source

      The ‘Mitofusins and outer mitochondrial membrane fusion’ section (page unavailable) describes mitofusin oligomerization as part of outer-membrane fusion. It does not say that an increase in mitochondrial membrane potential triggers fusion; the passage addressing membrane potential instead describes a drop associated with inner-membrane constriction. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim.

    Premisecitation

    Astrocytes play a fundamental role in AD pathology.

    “Also, although astrocytes play a fundamental role in AD pathology12, little is known about APOE4 effect on their mitochondria.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [12] Lampinen, R., Belaya, I., Boccuni, I., Malm, T., Kanninen, K. M. in Astrocyte – Physiology and Pathology (ed. D’Amato MTGaLC), INTECH 139–162 (2018). https://doi.org/10.5772/intechopen.71825. source

  • The quote only partly states this claim.

    Interpretationown data

    APOE3 astrocytes have higher autophagic flux than APOE4 astrocytes.

    “indicating higher autophagic flux30”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [30] Klionsky, D. J. et al. Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy 12, 1–222 (2016). source

      The Introduction (p. 28) explains how autophagic flux should be measured, and the Atg8/LC3 section (p. 56) cautions that LC3 levels alone do not establish flux. Searches for APOE3, APOE4, and their comparison in astrocytes found no passage reporting higher flux in APOE3 astrocytes. Our copy is truncated, so the comparison cannot be verified from it. (LLM, conf=0.72)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Mitochondrial dynamics include fusion, fission, and degradation events, linked to mitochondrial function.

    “Mitochondrial dynamics include fusion, fission, and degradation events, linked to mitochondrial function3,4.”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [3] Eisner, V., Picard, M. & Hajnoczky, G. Mitochondrial dynamics in adaptive and maladaptive cellular stress responses. Nat. Cell Biol. 20, 755–765 (2018). source
    • cites [4] Tilokani, L., Nagashima, S., Paupe, V. & Prudent, J. Mitochondrial dynamics: overview of molecular mechanisms. Essays Biochem. 62, 341–360 (2018). source

      The Abstract defines mitochondrial dynamics as coordinated cycles of fission and fusion, and the Introduction links those transitions to mitochondrial function. The section on post-translational modifications says fission can promote degradation of damaged mitochondria, but the paper does not define degradation itself as a mitochondrial dynamics event. Page numbers were not supplied in our copy. (LLM, conf=0.87)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Mitophagy proceeds mitochondrial fission and is triggered by decreased MMP.

    “Mitophagy proceeds mitochondrial fission and is triggered by decreased MMP5.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [5] Pickles, S., Vigie, P. & Youle, R. J. Mitophagy and quality control mechanisms in mitochondrial maintenance. Curr. Biol. 28, R170–R185 (2018). source

      The 'Mitophagy in Yeast' section links PINK1/Parkin-dependent mitophagy to mitochondrial transmembrane potential, but says depolarization does not appear necessary for several other mitophagy pathways. The 'Quality control at the sub-organelle level' section describes fission and autophagosome formation as coupled, and cites a yeast-specific proposal that fission acts upstream of mitophagy. It does not support an unqualified sequence between fission and mitophagy or decreased MMP as a universal trigger. Page numbers are unavailable in our copy. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Parkin labels mitochondria for mitophagy by ubiquitinating specific mitochondrial proteins; parkin is then degraded by the proteasome/lysosome due to autoubiquitination.

    “Parkin labels mitochondria for mitophagy by ubiquitinating specific mitochondrial proteins; parkin is then degraded by the proteasome/lysosome due to autoubiquitination26–29.”
    Quote in the paperSubstantial claim4 of 4 sources checked
    • cites [26] Vives-Bauza, C. et al. PINK1-dependent recruitment of Parkin to mitochondria in mitophagy. Proc. Natl Acad. Sci. USA 107, 378–383 (2010). source

      The Abstract reports that Parkin relocates to mitochondria and, with PINK1, helps deliver damaged mitochondria for autophagic degradation. It does not show that Parkin labels mitochondria by ubiquitinating specific mitochondrial proteins or that Parkin itself is degraded by the proteasome or lysosome following autoubiquitination; the degradation described is of mitochondria. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [27] Narendra, D., Tanaka, A., Suen, D. F. & Youle, R. J. Parkin is recruited selectively to impaired mitochondria and promotes their autophagy. J. Cell Biol. 183, 795–803 (2008). source

      The Results and discussion (page not provided) show that Parkin is recruited to impaired mitochondria and promotes their autophagic degradation; the Introduction identifies Parkin as a ubiquitin ligase. Our copy does not establish that Parkin labels mitochondria by ubiquitinating specific mitochondrial proteins, or that Parkin itself is degraded by the proteasome or lysosome because of autoubiquitination. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [28] Seirafi, M., Kozlov, G. & Gehring, K. Parkin structure and function. FEBS J. 282, 2076–2088 (2015). source

      The Introduction and “Parkin is an RBR E3 ubiquitin ligase” section say that parkin ubiquitinates outer mitochondrial membrane proteins, marking damaged mitochondria for mitophagy. The latter section says K6 ubiquitination of parkin may play a role in its own degradation; it does not establish that parkin is subsequently degraded by the proteasome or lysosome because of autoubiquitination. (LLM, conf=0.90)

      Experimental — accuracy not yet measured
    • cites [29] Rakovic, A. et al. Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1)-dependent ubiquitination of endogenous Parkin attenuates mitophagy: study in human primary fibroblasts and induced pluripotent stem cell-derived neurons. J. Biol. Chem. 288, 2223–2237 (2013). source

      The Discussion reports Parkin-mediated ubiquitination of multiple outer mitochondrial membrane proteins and says endogenous Parkin is self-ubiquitinated and likely degraded through the ubiquitin–proteasome system. It does not support lysosomal degradation of Parkin, and describes proteasomal degradation as likely rather than established. Page numbers are not available in our copy. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S2 (checkable).

    Premisecitation

    The mechanism of mitochondrial deterioration in astrocytes in AD is vague.

    “the mechanism is vague12.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [12] Lampinen, R., Belaya, I., Boccuni, I., Malm, T., Kanninen, K. M. in Astrocyte – Physiology and Pathology (ed. D’Amato MTGaLC), INTECH 139–162 (2018). https://doi.org/10.5772/intechopen.71825. source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Mitochondrial fusion is mediated by mitofusins, which are regulated by transcription and protein modification, including ubiquitination.

    “Mitochondrial fusion is mediated by mitofusins, which are regulated by transcription and protein modification, including ubiquitination3.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [3] Eisner, V., Picard, M. & Hajnoczky, G. Mitochondrial dynamics in adaptive and maladaptive cellular stress responses. Nat. Cell Biol. 20, 755–765 (2018). source

  • May combine two claims.

    Interpretationreasoning

    Less quality control and mitochondrial turnover is possible in APOE4 astrocytes, leading to increased population of dysfunctional mitochondria.

    “Therefore, less quality control and mitochondrial turnover is possible, leading to increased population of dysfunctional mitochondria50.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [50] Andres, A. M., Stotland, A., Queliconi, B. B. & Gottlieb, R. A. A time to reap, a time to sow: mitophagy and biogenesis in cardiac pathophysiology. J. Mol. Cell. Cardiol. 78, 62–72 (2015). source

      The Introduction (page unavailable) states that mitochondrial turnover eliminates dysfunctional mitochondria and that impaired quality control leads to their accumulation. The paper does not establish that quality control or turnover is reduced in APOE4 astrocytes; it provides the general mechanism, not that cell-specific finding. (LLM, conf=0.85)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingcitation

    Ubiquitination/proteasomal degradation of Mfn1 and Tom40, as well as of total mitochondrial ubiquitin, are reduced in APOE4 astrocytes.

    “the ubiquitination/proteasomal degradation of Mfn1 and Tom408,35, as well as of total mitochondrial ubiquitin, are reduced in the APOE4 astrocytes”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [8] Truban, D., Hou, X., Caulfield, T. R., Fiesel, F. C. & Springer, W. PINK1, parkin, and mitochondrial quality control: what can we learn about Parkinson’s disease pathobiology? J. Parkinson’s Dis. 7, 13–29 (2017). source

      The PINK1/Parkin-Directed Mitochondrial Quality Control section says Mitofusin-1 is targeted for elimination via the 26 S proteasome. The passages found do not establish proteasomal degradation of Tom40 or reduced ubiquitination and degradation in APOE4 astrocytes. No page number was available in our copy. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • cites [35] Yoshii, S. R., Kishi, C., Ishihara, N. & Mizushima, N. Parkin mediates proteasome-dependent protein degradation and rupture of the outer mitochondrial membrane. J. Biol. Chem. 286, 19630–19640 (2011). source

      The OMM Protein Degradation Is Inhibited by Proteasome Inhibitors section reports proteasome-dependent Tom40 degradation, and the Discussion reports proteasome-dependent mitofusin 1 degradation. But the Discussion says it is unknown whether these proteins are directly ubiquitinated by Parkin. The APOE4-astrocyte reduction is the citing authors’ own finding, not a result attributed to this source by the citation placement. (LLM, conf=0.85)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Abnormal parkin ubiquitination prevents its proteasomal degradation and impedes parkin-mediated mitophagy.

    “abnormal parkin ubiquitination was shown to prevent its proteasomal degradation and impede parkin-mediated mitophagy44.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [44] Durcan, T. M. et al. USP8 regulates mitophagy by removing K6-linked ubiquitin conjugates from parkin. EMBO J. 33, 2473–2491 (2014). source

      The paper reports that increased K6-linked ubiquitin conjugates on parkin delay parkin-mediated mitophagy (figure legend, “Viral-mediated infection and lysis of cortical neurons”; page unavailable). It also reports that reduced USP8 activity appears to protect parkin from degradation, but says K6-linked ubiquitination is *likely* to protect it from degradation in the proteasome **or lysosome** (“USP8 selectively removes K6-linked ubiquitin conjugates from parkin” and discussion; pages unavailable). The claim overstates this as demonstrated prevention of proteasomal degradation specifically. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Other studies have demonstrated impaired mitophagy and parkin accumulation in AD neurons.

    “other studies have demonstrated impaired mitophagy and parkin accumulation in AD neurons45,46.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [45] Kerr, J. S. et al. Mitophagy and Alzheimer’s disease: cellular and molecular mechanisms. Trends Neurosci. 40, 151–166 (2017). source
    • cites [46] Ye, X., Sun, X., Starovoytov, V. & Cai, Q. Parkin-mediated mitophagy in mutant hAPP neurons and Alzheimer’s disease patient brains. Hum. Mol. Genet. 24, 2938–2951 (2015). source

      The Discussion reports inadequate capacity to clear damaged mitochondria despite enhanced induction of mitophagy, so the unqualified phrase “impaired mitophagy” misses that distinction. The section on increased Parkin translocation reports greater recruitment of Parkin to depolarized mitochondria in AD neurons, not overall Parkin accumulation; the patient-brain results instead report declining Parkin levels. Page numbers are unavailable in our copy. (LLM, conf=0.87)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Interpretationreasoning

    The mitochondrial network in APOE4 astrocytes is in a static hyperfused state, with less fission/degradation and reduced mitochondrial biogenesis.

    “suggesting that their mitochondrial network is in a static hyperfused state49; i.e., less fission/degradation occurs together with reduced mitochondrial biogenesis.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [49] Hoitzing, H., Johnston, I. G. & Jones, N. S. What is the function of mitochondrial networks? A theoretical assessment of hypotheses and proposal for future research. BioEssays: N. Rev. Mol., Cell. Dev. Biol. 37, 687–700 (2015). source

      In “Quantitative definitions of micro, meso- and hyperfusion” (page unavailable), the paper defines static hyperfusion as a highly fused state with rare or almost no fission events. It does not establish that APOE4 astrocytes are in that state or that they have reduced mitochondrial degradation and biogenesis. (LLM, conf=0.87)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Rapamycin promotes autophagosome formation and induces mitophagy by upregulating the parkin/PINK1 pathway.

    “rapamycin, which promotes autophagosome formation30, and was shown to induce mitophagy by upregulating the parkin/PINK1 pathway25,40–42.”
    Quote in the paperSubstantial claim2 of 5 sources checked
    • cites [30] Klionsky, D. J. et al. Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy 12, 1–222 (2016). source
    • cites [25] Ebrahimi-Fakhari, D. et al. Impaired mitochondrial dynamics and mitophagy in neuronal models of tuberous sclerosis complex. Cell Rep. 17, 2162 (2016). source

      The available indexed passages are from a correction notice (p. 2162), chiefly its Acknowledgments, rather than the study’s findings. Searches for rapamycin, mitophagy, and the Parkin/PINK1 pathway found no passage addressing whether rapamycin induces mitophagy through that pathway; the decisive study text appears to be missing from our copy. (LLM, conf=0.72)

      Experimental — accuracy not yet measured
    • cites [40] Bartolome, A. et al. MTORC1 regulates both general autophagy and mitophagy induction after oxidative phosphorylation uncoupling. Mol. Cellular Biol. 37, e00441 (2017). source
    • cites [41] Li, Q. et al. Rapamycin attenuates mitochondrial dysfunction via activation of mitophagy in experimental ischemic stroke. Biochem. Biophys. Res. Commun. 444, 182–188 (2014). source
    • cites [42] Wang, C. et al. The post-therapeutic effect of rapamycin in mild traumatic brain-injured rats ensuing in the upregulation of autophagy and mitophagy. Cell Biol. Int. 41, 1039–1047 (2017). source

  • Classified as probably not a substantial claim.

    Premisecitation

    During mitophagy, parkin ubiquitinates Mfn1, leading to its proteasomal degradation and fusion inhibition.

    “During mitophagy, parkin ubiqitinates Mfn1, leading to its proteasomal degradation and fusion inhibition8,43.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [8] Truban, D., Hou, X., Caulfield, T. R., Fiesel, F. C. & Springer, W. PINK1, parkin, and mitochondrial quality control: what can we learn about Parkinson’s disease pathobiology? J. Parkinson’s Dis. 7, 13–29 (2017). source
    • cites [43] Glauser, L., Sonnay, S., Stafa, K. & Moore, D. J. Parkin promotes the ubiquitination and degradation of the mitochondrial fusion factor mitofusin 1. J. Neurochem. 118, 636–645 (2011). source

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Changes in mitochondrial dynamics and mitochondrial dysfunction are recognized as hallmarks of AD.

    “Changes in mitochondrial dynamics and mitochondrial dysfunction are recognized as hallmarks of AD”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [12] Lampinen, R., Belaya, I., Boccuni, I., Malm, T., Kanninen, K. M. in Astrocyte – Physiology and Pathology (ed. D’Amato MTGaLC), INTECH 139–162 (2018). https://doi.org/10.5772/intechopen.71825. source

  • Classified as probably not a substantial claim.

    Premisecitation

    APOE4 is associated with changes in mitochondrial dynamics proteins expression in transgenic mice brains.

    “as well as with changes in mitochondrial dynamics proteins expression in transgenic mice brains15.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [15] Simonovitch, S., Schmukler, E., Masliah, E., Pinkas-Kramarski, R. & Michaelson, D. M. The effects of APOE4 on mitochondrial dynamics and proteins in vivo. J. Alzheimers Dis. 70, 861–875 (2019). source

  • May combine two claims.

    Findingown data

    Rapamycin enhances mitophagy and improves mitochondrial functioning in APOE4 astrocytes.

    “Importantly, the autophagy inducer rapamycin enhanced mitophagy and improved mitochondrial functioning in APOE4 astrocytes.”
    • Also stated in: § Introduction · plain
      “Notably, induction of mitophagy by rapamycin restored mitochondrial function.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    CCCP treatment elevates mitochondrial LC3-II, more prominently in APOE3 astrocytes.

    “elevated mitochondrial LC3-II, which was more prominent in the APOE3 astrocytes”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The human APOE3 and APOE4 targeted-replacement astrocyte cell lines differ only in APOE genotype.

  • May combine two claims.

    Findingown data

    In APOE3/APOE4 astrocytes stably expressing Mito-GFP, CCCP treatment results in decreased number of branches per network, more profound in APOE3 astrocytes.

    “treatment with CCCP resulted in decreased number of branches per network, which was more profound in the APOE3 astrocytes”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The human APOE3 and APOE4 targeted-replacement astrocyte cell lines differ only in APOE genotype.

  • May combine two claims.

    Findingown data

    CCCP treatment induces a dose-dependent decrease of parkin and Mfn1 levels and increased LC3-II/LC3-I ratio, consistent with mitophagy induction.

    “CCCP treatment induced a dose-dependent decrease of parkin and Mfn1 levels (indicating their degradation) and increased LC3-II/LC3-I ratio (autophagosomes formation), consistent with mitophagy induction”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In APOE3 astrocytes, CCCP increases the number of autophagosomes containing mitochondria and the formation of spheroid mitochondria.

    “in the APOE3 astrocytes, CCCP increased the number of autophagosomes containing mitochondria and the formation of spheroid mitochondria”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The human APOE3 and APOE4 targeted-replacement astrocyte cell lines differ only in APOE genotype.

  • May combine two claims.

    Findingown data

    CCCP-induced LC3 puncta and co-localization with mitochondria are higher in APOE3 astrocytes than APOE4.

    “which was higher in APOE3 astrocytes”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The human APOE3 and APOE4 targeted-replacement astrocyte cell lines differ only in APOE genotype.

  • May combine two claims.

    Findingown data

    In CQ-treated cells, levels of LC3-II, p62 and ubiquitin in the mitochondrial fraction were higher in APOE3 than APOE4, but parkin levels did not differ.

    “although the levels of LC3-II, p62 and ubiquitin in the mitochondrial fraction of CQ-treated APOE3 cells were higher compared with APOE4 cells, the levels of parkin did not differ”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The human APOE3 and APOE4 targeted-replacement astrocyte cell lines differ only in APOE genotype.

  • May combine two claims.

    Findingown data

    Rapamycin treatment increased LC3-II/LC3-I ratio and decreased p62 levels in both APOE3/APOE4 astrocytes.

    “Rapamycin treatment increased LC3-II/LC3-I ratio and decreased p62 levels, in both the APOE3/APOE4 astrocytes (Fig. 6a)”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In APOE4 astrocytes, rapamycin restored mitochondrial metabolism (MTT), augmented MMP (MitoTracker Red), and corrected the altered medium pH without affecting cell number.

    “in the APOE4 astrocytes, rapamycin restored mitochondrial metabolism (MTT), augmented MMP (MitoTracker Red), and corrected the altered medium pH without affecting cell number (Fig. 6c–e).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Drp1 protein and mRNA levels and its mitochondrial recruitment are decreased in APOE4 astrocytes.

    “Drp1 protein and mRNA levels and its mitochondrial recruitment, are decreased in APOE4 astrocytes”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The interaction of autophagic proteins LC3-II and p62 with mitochondria, and the lysosomal degradation of mitochondrial LC3-II and p62, are reduced in APOE4 astrocytes.

    “the interaction of the autophagic proteins LC3-II and p62 with the mitochondria, and the lysosomal degradation of mitochondrial LC3-II and p62 are reduced in APOE4 astrocytes.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The mechanisms mediating APOE4 pathological effects remain unknown.

    “Nonetheless, the mechanisms mediating APOE4 pathological effects remain unknown1.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [1] Michaelson, D. M. APOE epsilon4: the most prevalent yet understudied risk factor for Alzheimer’s disease. Alzheimer’s Dement. 10, 861–868 (2014). source

  • May combine two claims.

    Interpretationown data

    Parkin undergoes ubiquitination in APOE4 astrocytes, yet it is not degraded by the proteasome.

    “Therefore, the results indicate that parkin undergoes ubiquitination in APOE4 astrocytes, yet it is not degraded by the proteasome.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    Immunoreactive bands were visualized within the linear range to enable accurate quantification.

    “Bands were visualized by Amersham Imager 600 within the linear range, employing the Automatic/Semi-autmatic exposure options, which allows optimal exposure times below saturation to enable accurate quantification (according to manufacturer instructions).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The increased mitochondrial parkin and ubiquitin in APOE4 astrocytes indicate either increased recruitment of parkin and ubiquitination of mitochondria, or accumulation due to reduced mitochondrial degradation.

    “indicating either increased recruitment of parkin and ubiquitination of mitochondria, or accumulation due to reduced mitochondrial degradation”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    APOE4 expression is associated with altered mitochondrial dynamics, which might lead to impaired mitochondrial function in astrocytes.

    “Collectively, the results demonstrate that APOE4 expression is associated with altered mitochondrial dynamics, which might lead to impaired mitochondrial function in astrocytes.”
    • Also stated in: § Introduction · hedged
      “Taken together, the results suggest that impaired mitochondrial dynamics in APOE4 astrocytes is involved in mitochondrial dysfunction”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    APOE4 astrocytes have dysfunctional fission and mitophagy following mitochondrial damage.

    “Taken together, the results further demonstrate dysfunctional fission and mitophagy in the APOE4 astrocytes following mitochondrial damage.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    APOE4 astrocytes have less mitochondrial fission and less association of LC3 with mitochondria.

    “indicating less mitochondrial fission and association of LC3 with mitochondria in APOE4 astrocytes”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Parkin undergoes reduced mitophagic and proteasomal degradation in APOE4 astrocytes.

    “indicating its reduced mitophagic and proteasomal degradation, respectively, in the APOE4 astrocytes.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    The study was conducted according to NIH Guidelines and approved by the Animal Care Committee of TAU.

    “The study was conducted according to the NIH Guidelines for Use and Care of Laboratory Animals, following the approval by Animal Care Committee of TAU (#L-04-16-002).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Mitochondria of APOE4 astrocytes exhibit reduced fission and mitophagy.

    “We found that APOE3 and APOE4 astrocytes differ in their mitochondrial dynamics, suggesting that the mitochondria of APOE4 astrocytes exhibit reduced fission and mitophagy.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The human APOE3 and APOE4 targeted-replacement astrocyte cell lines differ only in APOE genotype.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    All experiments were performed at least 3 times.

    “All experiments were performed at least 3 times.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Following CCCP treatment, less fission and association of LC3-II with damaged mitochondria occurs in APOE4 astrocytes.

    “This suggests that following treatment, less fission and association of LC3-II with damaged mitochondria occurs in APOE4 astrocytes.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Rapamycin treatment enhanced autophagosome formation and cargo degradation.

    “indicating enhanced autophagosome formation and cargo degradation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    Less autophagosomes-lysosomes fusion in APOE4 astrocytes following CCCP is consistent with other lysosomal dysfunctions associated with APOE4.

    “which is consistent with other lysosomal dysfunctions associated with APOE447.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [47] Schmukler, E., Michaelson, D. M. & Pinkas-Kramarski, R. The interplay between apolipoprotein E4 and the autophagic-endocytic-lysosomal axis. Mol. Neurobiol. 55, 6863–6880 (2018). source

  • Classified as probably not a substantial claim.

    Premisecitation

    APOE4 is a risk factor for AD.

    “Among the risk factors for AD is the APOE4 allele1”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [1] Michaelson, D. M. APOE epsilon4: the most prevalent yet understudied risk factor for Alzheimer’s disease. Alzheimer’s Dement. 10, 861–868 (2014). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationown data

    The elevated FL-PINK1 levels by rapamycin probably result from enhanced PINK1 mRNA synthesis.

    “which probably results from enhanced PINK1 mRNA synthesis (Fig. 6b).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Reduced Drp1 levels and recruitment indicate reduced mitochondrial fission in APOE4 astrocytes.

    “indicating reduced mitochondrial fission.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Reduced Mfn1 ubiquitination/degradation leads to increased Mfn1 levels and fusion, possibly interfering with mitophagy.

    “leading to increased Mfn1 levels and fusion, possibly interfering with mitophagy.”
    Quote in the paperSubstantial claim
60 of 60

  • The paper relies on this without support.

    The effect of APOE4 on mitochondrial dynamics was less studied.

    “yet the effect of APOE4 on mitochondrial dynamics was less studied”

  • The paper relies on this without support.

    Little is known about the effect of APOE4 on astrocyte mitochondria.

    “little is known about APOE4 effect on their mitochondria”

  • The paper relies on this without support.

    The human APOE3 and APOE4 targeted-replacement astrocyte cell lines differ only in APOE genotype.

    “The human APOE3 and APOE4 targeted-replacement astrocyte cell lines were previously described16.”

  • The authors state this as an assumption.

    Impaired removal of damaged mitochondria underlies APOE4 astrocytes mitochondrial dysfunction.

    “Assuming that impaired removal of damaged mitochondria underlies APOE4 astrocytes mitochondrial dysfunction”

  • The paper relies on this without support.

    The effects of APOE4 on mitochondrial dynamics and dysfunction are unclear.

    “however, its effects on mitochondrial dynamics and dysfunction are unclear.”
5 of 5

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • APOE4 astrocytes have an increased number of lipid droplets and impaired glucose utilization and mitochondrial function.

    “APOE4 astrocytes have an increased number of lipid droplets and impaired glucose utilization and mitochondrial function, lending further support to this hypothesis143,146,147 (Fig. 2b).”

    From Multifaceted roles of APOE in Alzheimer disease (2024) · cites this paper as [147]

    The Results section, “APOE4 astrocytes exhibit impaired mitochondrial function” (page unavailable), reports reduced mitochondrial metabolism and ATP levels, supporting the mitochondrial-function part of the claim. Our copy does not report an increased number of lipid droplets or impaired glucose utilization; it describes lower medium pH as suggestive of increased compensatory glycolysis. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • APOEε4 is linked to altered expression of proteins involved in mitochondrial fission and fusion in both a mouse model and human postmortem brains, suggesting that an alteration in mitochondrial dynamics might lead to or arise from impaired mitochondrial function.

    “in both a mouse model and human postmortem brains, APOEε4 is linked to altered expression of proteins involved in mitochondrial fission and fusion, suggesting that an alteration in mitochondrial dynamics might lead to or arise from impaired mitochondrial function147,170.”

    From Multifaceted roles of APOE in Alzheimer disease (2024) · cites this paper as [147]

    Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

    Experimental — accuracy not yet measured

  • Several models of AD have demonstrated altered mitochondrial dynamics, not only in neurons, but also in astrocytes.

    “Several models of AD have demonstrated altered mitochondrial dynamics, not only in neurons, but also in astrocytes [71].”

    From Apoe4 and Alzheimer’s Disease Pathogenesis—Mitochondrial Deregulation and Targeted Therapeutic Strategies (2023) · cites this paper as [71]

    The Discussion reports altered mitochondrial dynamics in APOE4-expressing astrocytes and cites other studies of impaired mitophagy in AD neurons. It does not establish that several AD models have demonstrated the finding in astrocytes; its own astrocyte result concerns the APOE4 model. (LLM, conf=0.85)

    Experimental — accuracy not yet measured

  • ApoE4 inhibits Drp1 transcription and expression, which may be linked to disruption of mitochondrial fission.

    “It has been also suggested that ApoE4 inhibits Drp1 transcription and expression, which may be linked to the disruption of mitochondrial fission [71].”

    From Apoe4 and Alzheimer’s Disease Pathogenesis—Mitochondrial Deregulation and Targeted Therapeutic Strategies (2023) · cites this paper as [71]

    The Discussion reports decreased Drp1 mRNA and protein levels in APOE4 astrocytes and links them to reduced mitochondrial fission. The Results say the lower protein levels could result from decreased Drp1 mRNA synthesis, but do not establish that APOE4 directly inhibits transcription. The evidence is also specific to astrocytes. (LLM, conf=0.83)

    Experimental — accuracy not yet measured

  • ApoE4-expressing astrocytes alter mitochondrial dynamics and function.

    “ApoE4-expressing astrocytes alter mitochondrial dynamics and function [53]”

    From APOE4 genotype exacerbates the depression-like behavior of mice during aging through ATP decline (2021) · cites this paper as [53]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • AIF is labeled a cytosolic marker but used to normalize mitochondrial proteins

    Minor

    The Fig. 2 caption identifies AIF as the cytosolic marker, then says protein measurements in the mitochondrial fraction were normalized to AIF. These descriptions assign AIF conflicting roles in the same analysis.

1 of 1

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Related

Authors
Schmukler, E., Solomon, S., Simonovitch, S., Goldshmit, Y., Wolfson, E., Michaelson, D. M., & Pinkas-Kramarski, R.
Affiliations
Tel Aviv University (IL)
ORCID
Michaelson, Daniel Morris
Venue
Cell Death & Disease
Publisher
Springer Science and Business Media LLC
Published
2020-07-24
Volume
11
Issue
7
Pages
578-578
ISSN
2041-4889 (ISSN-L)
DOI
10.1038/s41419-020-02776-4
PMC
PMC7382473
OpenAlex
W3044056525
Semantic Scholar
9fa0c1c67d4017c08f026212ddf2c98325f1f7dd
Cited by
125
References
55
Citations by year
2026: 27 · 2025: 21 · 2024: 19 · 2023: 18 · 2022: 14 · 2021: 23 · 2020: 3
FWCI
4.70
Type
journal article
Language
en
Open access
Licence
Locations
  • Cell Death and Disease (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
Funders
The Prajs-Drimmer Institute for the Development of Anti-Degenerative Drugs and SAIA Fund for HIV and Parkinson’s Diseases Research, Tel Aviv University.
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Mitochondrial Function and Pathology
  • Health Sciences › Medicine › Physiology › Alzheimer's disease research and treatments
  • Health Sciences › Medicine › Epidemiology › Autophagy in Disease and Therapy
Keywords
APOE ε4, astrocytes, mitochondrial dynamics, mitochondrial fission, mitochondrial fusion, mitophagy, autophagy, mitochondrial function, rapamycin, Alzheimer's disease, APOE3
MeSH terms
Astrocytes, Carbonyl Cyanide m-Chlorophenyl Hydrazone, Cell Line, Humans, Lysosomes, Mitochondria, Sirolimus, Mitochondrial Proteins, Proteasome Endopeptidase Complex, Apolipoprotein E3, Apolipoprotein E4, Ubiquitination, Proteolysis, Mitochondrial Dynamics

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-11-02.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-11-02.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

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