Hippocampal TMEM55B overexpression in the 5XFAD mouse model of Alzheimer's disease

5XFAD and other FAD mice do not display robust age- or pathology-associated cognitive deficits on hippocampal and non-hippocampal memory tasks.

“Despite the aggressive rate of pathological Aβ aggregation and lysosomal disruption in the 5XFAD and other FAD mice, they do not display robust ageor pathology-associated cognitive deficits on hippocampal and non-hippocampal memory tasks (Jankowsky & Zheng, 2017;Oblak et al., 2021)”

• cites Jankowsky & Zheng, 2017 sourceDisputed

  The Cognitive impairment subsection says that nearly all tested APP-overexpression models show spatial learning and memory deficits, and specifically reports cognitive decline in 5XFAD months after amyloid pathology. It cautions that the age and disease stage at which deficits are detected depend on the task, but does not support the categorical claim that these mice lack such deficits. (LLM, conf=0.88)

  Checked by a reasoning model — may be wrong.

  Experimental — accuracy not yet measured
• cites Oblak et al., 2021 sourcePartly supported

  The Results section reports no spatial working-memory deficit in 5XFAD mice at 6 or 12 months on a hippocampal spontaneous-alternation task. The Discussion likewise reports no consistent cognitive impairment in the tested mice, but says cognitive testing was limited in scope. The paper does not establish the claim for other FAD mice or for non-hippocampal memory tasks. (LLM, conf=0.88)

  Experimental — accuracy not yet measured

TMEM55B expression is dependent on TFEB.

“Interestingly, while TMEM55B expression is dependent on TFEB (Willett et al., 2017), TMEM55B can actually inhibit TFEB nuclear translocation (Hashimoto et al., 2018) thus suppressing expression of lysosomal genes.”

• cites Willett et al., 2017 sourcePartly supported

  The Results section, “TFEB and TFE3 upregulate TMEM55B in response to starvation,” reports that TFEB increases TMEM55B mRNA and protein and that the starvation-induced increase is TFEB/TFE3-dependent. The claim omits both the starvation condition and TFE3’s role, making TFEB dependence sound more general than the evidence establishes. (LLM, conf=0.85)

  Experimental — accuracy not yet measured

TMEM55B gene expression does not change throughout the lifespan of 5XFAD mice.

“Notably, TMEM55B gene expression does not change throughout the lifespan of 5XFAD mice, but LAMP1, TFEB, and TFE3 gene expression increases after 12 months of age (Forner et al., 2021).”

• cites Forner et al., 2021 sourceCould not verify

  The Technical Validation section, “Gene expression changes in 5xFAD mice” (Fig. 8; page unavailable), reports age-related changes in differentially expressed genes but does not identify TMEM55B or establish that its expression remains unchanged. Searches for TMEM55B and for LAMP1, TFEB, and TFE3 expression after 12 months found no passage in our copy establishing the cited sentence’s gene-specific claims. (LLM, conf=0.72)

  Experimental — accuracy not yet measured

Dysfunction of the endosomal-lysosomal system is directly linked with Aβ deposition.

“Dysfunction of the endosomallysosomal system is also directly linked with Aβ deposition (Lee et al., 2022), oxidative stress (Wendt et al., 2022), and synaptic dysfunction (Adalbert et al., 2009).”

• cites Lee et al., 2022 sourceSupported

Overall hippocampal LAMP1 signal intensity did not differ among genotype or treatment groups.

“Although LAMP1 signal intensity was equal among all experimental groups (F (1, 14) = 0.7831, p = 0.3911, main effect of genotype; F (1,14) = 0.3892, p = 0.5428, main effect of treatment; Figure 3B),”

LAMP1 fluorescence intensity is strongly enriched within the PPR.

“(F) LAMP1 fluorescence intensity is strongly enriched within the PPR, and PPR LAMP1 intensity is slightly reduced by AAV-55B treatment.”

Within peri-plaque regions, LAMP1 signal intensity is nearly two-fold greater than the average for the whole hippocampal section.

“Within PPRs, LAMP1 signal intensity was nearly two-fold greater than the average for the whole hippocampal section (2-way ANOVA, F (1, 8) = 263.6,p < 0.0001, main effect of ROI, Figure 3F).”

In 5XFAD mice, AAV-TMEM55B-GFP treatment reduced LAMP1 intensity in regions surrounding Aβ plaques.

“Notably, we observed that LAMP1 intensity in regions surrounding Aβ plaques was reduced (Figure 3F)”

• Also stated in: § Abstract · plain

  “PPR LAMP1 intensity is slightly reduced by AAV-55B treatment.”

In 5XFAD mice, enlarged LAMP1+ vacuoles surrounding Aβ plaques were observed.

“In the present study, enlarged LAMP1+ vacuoles surrounding Aβ plaques were observed”

No significant difference was observed in hippocampal LAMP1 and Aβ immunopositive percent area.

“However, when we assessed hippocampal LAMP1 and Aβ immunopositive percent area (Figure 3C-D), we did not observe a significant difference.”

Saline- and AAV-TMEM55B-GFP-injected mice did not differ in peri-plaque-region LAMP1-positive area normalized as percent of hippocampal area.

“Saline and AAV-TMEM55B-GFP injected mice did not differ in PPR LAMP1 positive area normalized as percent of hippocampal area (p = 0.9729).”

LAMP1 percent of hippocampal area is reduced in 5XFAD mice compared to WT.

“(C) LAMP1 percent of hippocampal area is reduced in 5XFAD mice compared to WT”

Wild-type mice displayed significantly greater hippocampal LAMP1-positive area than 5XFAD mice.

“WT mice displayed significantly greater LAMP1 positive area (F (3, 14) = 27.96,main effect of genotype; Figure 3C).”

Treatment with AAV-TMEM55B-GFP did not affect overall hippocampal LAMP1 area in 5XFAD mice.

“Treatment with AAV-TMEM55B-GFP did not affect overall hippocampal LAMP1 (F (1, 14) = 0.0002968, p = 0.9865, main effect of treatment; Figure 3C) or Aβ (D54D2) plaque signal area (p = 0.7542; Figure 3D).”

Mice learned the location of the hidden platform during the Morris water maze regardless of treatment or genotype (significant main effect of time).

“Mice learned the location of the hidden platform during MWM regardless of treatment or genotype (repeated measures 3-way ANOVA, F (4, 64) = 50.8,p<0.0001, main effect of time, Figure 1A).”

Mice performed equivalently on the Morris water maze probe trial of spatial memory regardless of genotype or treatment, measured as number of passes over and distance to the platform location.

“Mice performed equivalently on the MWM probe trial of spatial memory regardless of genotype or treatment when measured as number of passes over the platform location (2-way ANOVA, F (1, 16) = 0.05202, p = 0.8225, main effect of genotype; F (1, 16) = 0.7511, p = 0.3989, main effect of treatment; Figure 1B) and distance to platform location (2-way ANOVA F (1, 16) = 1.101, p = 0.3097, main effect of”

No difference in hippocampal LAMP1 intensity with respect to genotype or AAV-55B.

“(B) No difference in hippocampal LAMP1 intensity with respect to genotype or AAV-55B”

No difference in LAMP1 percent of hippocampal area within the PPR.

“(G) No difference in LAMP1 percent of hippocampal area within the PPR.”

Hippocampal overexpression of TMEM55B in 5XFAD mice modestly but significantly reduces peri-plaque LAMP1 immunopositivity (LAMP1 intensity within peri-plaque regions) relative to saline-treated 5XFAD mice.

“Further, 5XFAD mice treated with AAV-TMEM55B-GFP exhibit modestly but significantly reduced LAMP1 intensity than those treated with saline (F (1, 8) = 8.363, p = 0.02, main effect of treatment, Figure 3F).”

• Also stated in: § Abstract · plain

  “In the present study, we find that hippocampal overexpression of TMEM55B modestly reduces peri-plaque LAMP1 immunopositivity.”

• Also stated in: § Abstract · plain

  “Immunohistochemical analyses revealed a modest but significant reduction in the accumulation of endo-lysosomes in dystrophic neurites surrounding Aβ plaques, but there was no change in hippocampal-dependent memory or plaque load.”

• AssumptionRests on an assumption: LAMP1 immunopositivity within peri-plaque regions quantitatively reflects the accumulation of dysfunctional endo-lysosomes in dystrophic neurites.

No spatial cognitive/memory deficits were detected in the paper's 5XFAD mice with respect to genotype or treatment.

“Although we were unable to detect any cognitive deficits in our 5XFAD mice”

• Also stated in: § Abstract · plain

  “Mice display no spatial cognitive/memory deficits with respect to genotype or treatment.”

Treatment with AAV-TMEM55B-GFP did not change amyloid β (D54D2) plaque signal area in 5XFAD mice.

“Treatment with AAV-TMEM55B-GFP did not affect overall hippocampal LAMP1 (F (1, 14) = 0.0002968, p = 0.9865, main effect of treatment; Figure 3C) or Aβ (D54D2) plaque signal area (p = 0.7542; Figure 3D).”

5XFAD mice spent significantly more time in the target quadrant than wild-type mice.

“Unexpectedly, 5XFAD mice spent significantly more time in the target quadrant than WT mice (2-way ANOVA, F (1, 16) = 8.725, p = 0.0093, main effect of genotype, Figure 1C).”

TMEM55B overexpression altered LAMP1 localization in 5XFAD mice.

“Overall, these functions align with the data herein demonstrating that TMEM55B overexpression altered LAMP1 localization in 5XFAD mice.”

Restoration of retrograde transport of endo-lysosomes may represent a therapeutic strategy to reduce dystrophic neurite pathology as well as amyloid β deposition and neurodegeneration in Alzheimer's disease.

“Therefore, restoration of retrograde transport of endo-lysosomes may represent a therapeutic strategy to reduce not only dystrophic neurite pathology but also Aβ deposition and neurodegeneration during AD.”

Retrograde transport of autophagic vacuoles is essential for their maturation to functional lysosomes.

“Importantly, retrograde transport of these autophagic vacuoles is essential for their maturation to functional lysosomes (Nixon, 2017).”

• cites Nixon, 2017 sourceNot checked — no full text of the source

The endosomal-lysosomal network is dysfunctional in Alzheimer's disease, evident from the accumulation of autophagic vacuoles in the axons of dystrophic neurites due to disruption of retrograde trafficking, acidification and maturation of endo-lysosomes.

“The endosomal-lysosomal network is dysfunctional in Alzheimer's disease (AD), evident from the accumulation of autophagic vacuoles in the axons of dystrophic neurites due to disruption of retrograde trafficking, acidification, and maturation of endo-lysosomes (Gowrishankar et al., 2015;Lie et al., 2022;Sadleir et al., 2016;Serrano-Pozo et al., 2016).”

• cites Gowrishankar et al., 2015 sourceNot checked yet
• cites Lie et al., 2022 sourceCheck pending
• cites Sadleir et al., 2016 sourceNot checked yet

TMEM55B (PIP4P1) is a key player in the retrograde trafficking of lysosomes in multiple cell types.

“Transmembrane protein 55B (TMEM55B), also known as phosphatidylinositol-4,5bisphosphate 4-phosphatase 1 (PIP4P1), is a key player in the retrograde trafficking of lysosomes in multiple cell types (Araki & Kontani, 2021;Rudnik et al., 2022;Takemasu et al., 2019;Willett et al., 2017).”

• cites Araki & Kontani, 2021 sourceNot checked — no full text of the source
• cites Rudnik et al., 2022Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Willett et al., 2017 sourceNot checked yet

  A check is scheduled.

Other pathological processes may be important for cognitive dysfunction in AD.

“suggesting other pathological processes may be important for cognitive dysfunction in AD.”

5XFAD mice at 2 months of age are at the very earliest stages of amyloid β plaque development.

“at 2 months of age to intervene in adult mice at the very earliest stages of Aβ plaque development (Forner et al., 2015;Oblak et al., 2021).”

• cites Forner et al., 2015Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Oblak et al., 2021 sourceNot checked yet

Knockout of TMEM55B leads to lysosomal stress and loss of vATPase function related to lysosomal acidification.

“Knockout of TMEM55B leads to lysosomal stress and loss of vATPase function which is related to the acidification of lysosomes (Hashimoto et al., 2018).”

• cites Hashimoto et al., 2018 sourceNot checked — no full text of the source

The observed enlarged LAMP1+ vacuoles surrounding Aβ plaques demonstrate endosomal-lysosomal network dysfunction in 5XFAD mice.

“demonstrating the endosomal-lysosomal network dysfunction in 5XFAD mice (Figure 3).”

TMEM55B expression reduced vacuolar accumulation in neurons surrounding Aβ plaques.

“suggesting that TMEM55B expression reduced vacuolar accumulation in neurons surrounding Aβ plaques.”

LAMP1, TFEB, and TFE3 gene expression increases after 12 months of age in 5XFAD mice.

“Notably, TMEM55B gene expression does not change throughout the lifespan of 5XFAD mice, but LAMP1, TFEB, and TFE3 gene expression increases after 12 months of age (Forner et al., 2021).”

• cites Forner et al., 2021 sourceNot checked yet

Early defects in endo-lysosomal function in 5-month-old 5XFAD mice may not be driven by transcriptional regulation but instead by post-translational processes.

“These data suggest that early defects in endo-lysosomal function in 5-month-old 5XFAD mice herein may not be driven by transcriptional regulation but instead by post-translational processes and thus overexpression of TMEM55B may not be sufficient without altering post-translational processes that regulate TMEM55B function such as phosphorylation (Takemasu et al., 2019).”

Presenilin function is associated with dysfunctional lysosomal proteolysis and autophagy.

“Presenilin (PS) function, which is disrupted in patients with familial AD mutations in PS, is associated with dysfunctional lysosomal proteolysis and autophagy (Lee et al., 2010;Lie et al., 2022;Neely et al., 2011;Reddy et al., 2016)”

• cites Lee et al., 2010 sourceNot checked yet
• cites Lie et al., 2022 sourceCheck pending
• cites Neely et al., 2011 sourceCheck pending

The subtle changes observed in LAMP1 intensity surrounding Aβ plaques would be insufficient to modulate cognition in 5XFAD mice.

“it is likely that the subtle changes observed in the intensity of LAMP1 surrounding Aβ plaques would be insufficient to modulate cognition in 5XFAD mice.”

Local TMEM55B overexpression had a subtle effect on Aβ plaque-associated LAMP1 pathology in 5XFAD mice.

“Taken together, our results suggest that local TMEM55B overexpression had a subtle effect on Aβ plaque-associated LAMP1 pathology in 5XFAD mice.”

• Also stated in: § Abstract · boosted

  “The study herein demonstrates that TMEM55B overexpression has subtle effects on the intensity of LAMP1 surrounding Aβ plaques in 5XFAD mice.”

The data indicate a potential role for TMEM55B in reducing endo-lysosomal dysfunction during Alzheimer's-disease-like amyloid β pathology.

“Overall, these data indicate a potential role for TMEM55B in reducing endo-lysosomal dysfunction during AD-like Aβ pathology.”

• AssumptionRests on an assumption: LAMP1 immunopositivity within peri-plaque regions quantitatively reflects the accumulation of dysfunctional endo-lysosomes in dystrophic neurites.
• AssumptionRests on an assumption: AAV9-mediated hippocampal expression of TMEM55B-GFP yields functionally active TMEM55B in vivo.

Previous deep phenotyping of 5XFAD mice highlights the difficulty of modeling AD-like memory deficits in 5XFAD mice despite recapitulation of other AD-like phenotypes.

“Previous deep phenotyping of 5XFAD mice highlights the difficulty of modeling AD-like memory deficits in 5XFAD mice despite recapitulation of other AD-like phenotypes (Forner et al., 2015;Oblak et al., 2021).”

• cites Forner et al., 2015Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Oblak et al., 2021 sourceNot checked yet

Dysfunction of the endosomal-lysosomal system is directly linked with synaptic dysfunction.

“Dysfunction of the endosomallysosomal system is also directly linked with Aβ deposition (Lee et al., 2022), oxidative stress (Wendt et al., 2022), and synaptic dysfunction (Adalbert et al., 2009).”

• cites Adalbert et al., 2009 sourceNot checked — no full text of the source

TMEM55B regulates lysosome positioning and trafficking via interaction with the JIP4 motor protein adapter.

“TMEM55B regulates lysosome positioning and trafficking via interaction with the JIP4 motor protein adapter (Willett et al., 2017) independently from its phosphatase function (Takemasu et al., 2019) but dependent on S-palmitoylation (Rudnik et al., 2022).”

• cites Willett et al., 2017 sourceNot checked yet

5XFAD amyloid β pathology induces LAMP1 signal to translocate away from cell bodies and instead accumulate in axonal swellings in peri-plaque regions.

“Taken together, a change in area coverage without a change in intensity and the anatomical distribution within the representative images (Figure 3A and 2C middle panel) illustrate that 5XFAD Aβ pathology induces LAMP1 signal translocate away from cell bodies to instead accumulate in axonal swellings in peri-plaque regions (PPRs).”

• AssumptionRests on an assumption: LAMP1 immunopositivity within peri-plaque regions quantitatively reflects the accumulation of dysfunctional endo-lysosomes in dystrophic neurites.

TMEM55B-mediated feedback inhibition on TFEB translocation may underlie the subtle effect of TMEM55B overexpression on reducing peri-plaque LAMP1+ intensity in dystrophic neurites in 5XFAD mice.

“TMEM55B-mediated feedback inhibition on TFEB translocation may underlie the subtle effect of TMEM55B overexpression on reducing peri-plaque LAMP1+ intensity in dystrophic neurites in 5XFAD mice documented herein.”

Abnormalities in endosomal-lysosomal processing are an early event that precedes formation of Aβ plaques in numerous mouse models of Aβ pathology.

“However, abnormalities in endosomal-lysosomal processing is an early event that precedes the formation of Aβ plaques in numerous mouse models of Aβ pathology (Lee et al., 2022).”

• cites Lee et al., 2022 sourceNot checked yet

Dystrophic neurites are not entirely disrupted.

“However, these dystrophic neurites are not entirely disrupted (Adalbert et al., 2009), suggesting that restoration of trafficking could still result in neuroprotective benefit.”

• cites Adalbert et al., 2009 sourceNot checked — no full text of the source

Restoration of trafficking could still result in neuroprotective benefit.

“suggesting that restoration of trafficking could still result in neuroprotective benefit.”

Overexpression of TMEM55B may not be sufficient without altering post-translational processes that regulate TMEM55B function such as phosphorylation.

“These data suggest that early defects in endo-lysosomal function in 5-month-old 5XFAD mice herein may not be driven by transcriptional regulation but instead by post-translational processes and thus overexpression of TMEM55B may not be sufficient without altering post-translational processes that regulate TMEM55B function such as phosphorylation (Takemasu et al., 2019).”

• cites Takemasu et al., 2019 sourceNot checked — no full text of the source