The Alzheimer's Disease Gene SORL1 Regulates Lysosome Function in Human Microglia

SORL1 is highly expressed in the central nervous system, including in microglia.

“SORL1 is highly expressed in the central nervous system, including in microglia, the tissue‐resident immune cells of the brain.”

• Also stated in: § Introduction · plain

  “While SORL1 mRNA is highly expressed in microglia, even more so than in neurons and astrocytes (Lee et al. 2023; Olah et al. 2018; Zhang et al. 2016)”

• cites Lee et al. 2023 sourceSupported
• cites Olah et al. 2018 sourceCould not verify

  The Introduction identifies microglia as resident immune cells of the central nervous system, but that does not establish SORL1 expression. Searches for “SORL1” and “sortilin related receptor” found no passage in our copy stating that SORL1 is highly expressed in the CNS or in microglia. (LLM, conf=0.72)

  Experimental — accuracy not yet measured
• cites Zhang et al. 2016 sourceCould not verify

  The Results section on transcriptomes of purified brain cell types describes microglial gene-expression data, but it does not report SORL1 expression. Searches for SORL1 and its receptor name found no passage in our copy establishing that it is highly expressed in the CNS or in microglia; the indexed passages provide no page numbers. (LLM, conf=0.73)

  Experimental — accuracy not yet measured

Loss-of-function variants in SORL1 are causative for Alzheimer's disease.

“Loss of function variants in SORL1 are causative for Alzheimer's disease (ad)”

• Also stated in: § Introduction · boosted

  “Genetic, epidemiological, and functional studies have now cumulatively and unequivocally established SORL1 as a gene that increases the risk for ad”

• cites Holstege et al. 2017, 2023Not matched

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

• cites Kunkle et al. 2017 sourcePartly supported

  The ‘Variants in Known EOAD Genes’ section reports a SORL1 frameshift variant in two sisters, one with Alzheimer’s disease and one with mild cognitive impairment. The Discussion calls SORL1 a risk factor, while Table 1 lists the frameshift variant’s clinical significance as undetermined; the paper does not establish that SORL1 loss-of-function variants cause Alzheimer’s disease. Page numbers are unavailable in our copy. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites Lambert et al. 2013Not matched

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

Decreased expression of SORLA has been repeatedly observed in human AD brains.

“decreased expression of SORLA has been repeatedly observed in human ad brains”

• Also stated in: § Introduction · plain

  “Loss of SORLA expression has been observed in ad brains in the early stages of the disorder (Dodson et al. 2006; Scherzer et al. 2004; Thonberg et al. 2017).”

• cites Dodson et al. 2006 sourcePartly supported

  The Abstract and the section on LR11 expression in human tissue report reduced LR11/SorLA expression in sporadic AD brains, consistent with an earlier observation noted in the Discussion. But the Abstract also reports no reduction in familial AD brains, so the unqualified claim about human AD brains is too broad. (LLM, conf=0.90)

  Experimental — accuracy not yet measured
• cites Scherzer et al. 2004 sourceNot checked — no full text of the source
• cites Thonberg et al. 2017 sourcePartly supported

  The Results (Neuropathology and immunohistochemistry; page unavailable) report reduced SORL1 staining in the brains of two affected family members. The reduction was relative to both controls and sporadic AD cases; the paper does not establish that decreased SORLA expression has been repeatedly observed across human AD brains. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

SORLA binds to retromer.

“SORLA binds to retromer (Fjorback et al. 2012), which regulates the retrograde transport of the cation‐independent mannose‐6‐phosphate receptor (CIMPR) through the mannose‐6‐phosphate‐dependent pathway (M6P) (Arighi et al. 2004; Cui et al. 2019).”

• cites Fjorback et al. 2012 sourceSupported

There are several mechanisms by which SORLA-related trafficking can affect pro-inflammatory responses that are important in AD.

“As aberrant lysosome function can negatively impact the neuroimmune response of microglia (Quick et al. 2023; Van Acker et al. 2021), our data, along with that of Ovesen et al., suggests that there are several mechanisms by which SORLA‐related trafficking can affect pro‐inflammatory responses that are important in ad.”

• cites Quick et al. 2023 sourceSupported
• cites Van Acker et al. 2021 sourceSupported
• cites Ovesen et al.Not matched

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

Depletion of SORL1 may decrease the release of pro-inflammatory cytokines.

“Furthermore, the depletion of SORL1 may decrease the release of pro‐inflammatory cytokines either through conventional secretory routes from the TGN to the cell surface or by impairing LE, as observed in our study and others (Ovesen et al. 2024).”

• cites Ovesen et al. 2024 sourceSupported

We did not observe differences in the size of early endosomes between SORL1 WT and SORL1 KO hMGLs.

“We did not observe differences in the size of early endosomes between SORL1 WT and SORL1 KO hMGLs (Knupp et al. 2020) but have documented lysosomal enlargement in SORL1 KO microglia (Mishra 2024).”

• cites Knupp et al. 2020 sourceSupported

LE is used by microglia to release cytokines, enzymes, and cargo into the extracellular space.

“LE is used by microglia to release cytokines, enzymes, and cargo into the extracellular space (Dou et al. 2012; Jacquet et al. 2024; Kreher et al. 2021).”

• cites Dou et al. 2012 sourcePartly supported

  The Introduction says microglial lysosomes may be involved in cytokine release, and the Discussion reports lysosomal exocytosis of ATP (pp. 1022–1033). The paper does not show that microglia release enzymes through this mechanism; it identifies cathepsin D as a lysosomal marker, not as a released substance. Thus the broader list of released substances is not fully supported. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites Jacquet et al. 2024 sourcePartly supported

  The Results sections on lysosomal synapses and Aβ fibril secretion report microglial lysosomal exocytosis of contents into extracellular compartments, including enzymes and previously endocytosed Aβ cargo. They do not report cytokine release by this mechanism; the Limitations of the study mentions cytokines only as components absent from the model aggregates. No page numbers are available in our copy. (LLM, conf=0.88)

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

  Section 4.1, “Microglial Exocytosis,” describes microglial secretion of cytokines and an extracellular role for the lysosomal protease cathepsin S. It also discusses possible release of α-synuclein aggregates through lysosomal exocytosis. But it says the mechanism of microglial protein release is not fully understood and presents aggregate release as a theory, so it does not establish lysosomal exocytosis as the route for all three categories. (LLM, conf=0.84)

  Experimental — accuracy not yet measured

hMGLs cultured in isolation, in the absence of neurons and astrocytes, and in two-dimensional cultures may have altered inflammatory response and morphology.

“We acknowledge that since our hMGLs are cultured in isolation, in the absence of neurons and astrocytes, and in two‐dimensional cultures, their inflammatory response and morphology may be altered (Baxter et al. 2021).”

• cites Baxter et al. 2021 sourcePartly supported

  The Results sections on LPS responses and TGF-β2 signaling show that neuron–astrocyte cues alter microglial inflammatory responses and morphology compared with monoculture. However, the paper's microglia were rat or mouse, not human hMGLs, and it does not establish a separate effect of two-dimensional culture. Page numbers are unavailable in our copy. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Phagocytic uptake of fibrillar amyloid beta 1-42 is increased in SORLA-deficient hMGLs.

“Phagocytic uptake of fibrillar amyloid beta 1–42 and synaptosomes is increased in SORLA‐deficient hMGLs, but due to reduced lysosomal degradation, these substrates aberrantly accumulate in lysosomes.”

Loss of SORLA results in decreased lysosomal degradation in hMGLs.

“In this study, we show that loss of SORLA results in decreased lysosomal degradation and lysosomal enzyme activity due to altered trafficking of lysosomal enzymes in hMGLs.”

• Also stated in: § Loss of SORL1 Decreases Lysosomal Degradation in hMGLs · boosted

  “Overall, our data demonstrated that loss of SORL1 causes reduced lysosomal degradation in hMGLs.”

Both WT and SORL1 KO hMGLs showed an increase in MFI over a period of 2 h, indicating hiPSC-derived microglia were capable of lysosomal degradation in vitro.

“Both WT and SORL1 KO hMGLs showed an increase in MFI over a period of 2 h, suggesting our hiPSC‐derived microglia were capable of lysosomal degradation in vitro”

Loss of SORLA results in decreased lysosomal enzyme activity in hMGLs.

“In this study, we show that loss of SORLA results in decreased lysosomal degradation and lysosomal enzyme activity due to altered trafficking of lysosomal enzymes in hMGLs.”

• Also stated in: § Introduction · plain

  “We used quantitative flow cytometry, immunocytochemistry, and functional enzymatic and cellular assays to reveal that SORL1 KO hMGLs show decreased lysosomal degradation and reduced lysosomal enzymatic activity due to impaired trafficking of lysosomal enzymes from the trans‐Golgi network (TGN) to lysosomes.”

CIMPR has reduced co-localization with enzymes in lysosomes in SORL1-deficient hMGLs.

“We show that the main retromer cargo that functions with SORL1 to traffic lysosomal enzymes, CIMPR, has reduced expression in SORL1‐deficient hMGLs and reduced co‐localization with enzymes in lysosomes.”

SORL1 KO hMGLs demonstrated reduced MFI of DQ-Red-BSA compared to WT hMGLs at all time points tested.

“SORL1 KO hMGLs demonstrated reduced MFI of DQ‐Red‐BSA as compared to WT hMGLs at all time points tested (Figure 1B)”

Phagocytic uptake of synaptosomes is increased in SORLA-deficient hMGLs.

“Phagocytic uptake of fibrillar amyloid beta 1–42 and synaptosomes is increased in SORLA‐deficient hMGLs, but due to reduced lysosomal degradation, these substrates aberrantly accumulate in lysosomes.”

Lysosomal exocytosis is impaired in SORL1-deficient microglia.

“An alternative mechanism of lysosome clearance, lysosomal exocytosis, is also impaired in SORL1‐deficient microglia, which may contribute to an altered immune response.”

• Also stated in: § Introduction · plain

  “We tested lysosomal exocytosis (LE), a secretory pathway through which microglia release lysosomal enzymes, cargo, and inflammatory cytokines into the extracellular environment and found that this process is also altered in SORL1 KO hMGLs.”

CIMPR has reduced expression in SORL1-deficient hMGLs.

“We show that the main retromer cargo that functions with SORL1 to traffic lysosomal enzymes, CIMPR, has reduced expression in SORL1‐deficient hMGLs and reduced co‐localization with enzymes in lysosomes.”

SORL1 KO hMGLs show decreased extracellular secretion of pro-inflammatory cytokines IL-1β, IL-15, IP-10, TNF-α, and IL-8 and anti-inflammatory cytokines IL-10, IL-13, and IL-2.

“Specifically, SORL1 KO hMGLs showed decreased extracellular secretion of pro‐inflammatory cytokines IL‐1β, IL‐15, IP‐10, TNF‐α, and IL‐8 and anti‐inflammatory cytokines IL‐10, IL‐13, and IL‐2 (Figures S6 and S7).”

SORL1 KO hMGLs show increased uptake and sustained phagocytosis of fAβ and synaptosomes compared to WT hMGLs.

“To analyze uptake and phagocytosis, we incubated cells with fluorophore‐labeled fAβ and synaptosomes for 30 min, 5 h, and 24 h and observed increased uptake and sustained phagocytosis of both substrates in SORL1 KO hMGLs as compared to WT hMGLs (Figure S4D–G).”

SORL1 KO hMGLs show reduced protein levels of HEXB, Cathepsin B, and Cathepsin D in cell culture media upon treatment with calcimycin.

“We found reduced extracellular enzyme activity of HEXB, Cathepsin B, and Cathepsin D (Figure 6D–F) and reduced protein levels of all three lysosomal enzymes in cell culture media (Figure S3A–D) in SORL1 KO hMGLs upon treatment with a LE activator, calcimycin.”

Depletion of SORL1 did not alter protein expression of HEXB, CTSD, and CTSB in SORL1 KO hMGLs relative to WT hMGLs.

“Western blotting demonstrates loss of SORLA protein expression (D) but no change in total protein levels of immature and mature forms of HEXB (E‐F), Cathepsin B (G and H) and Cathepsin D (I and J) in SORL1 KO hMGLs relative to WT hMGLs.”

SORL1 KO hMGLs show a blunted response of multiple pro- and anti-inflammatory cytokines to LPS treatment and to IFNγ stimulation.

“Similar to their findings, we also observed a blunted response of multiple pro‐and anti‐inflammatory cytokines to LPS treatment, and we also show a blunted response to IFNγ stimulation.”

SORL1 KO hMGLs have increased uptake of BSA-594 compared to WT hMGLs.

“we observed an increased uptake of BSA‐594 in SORL1 KO hMGLs as compared to WT hMGLs (Figure 1C).”

SORL1 KO hMGLs show no difference in internalization of oligomeric Aβ compared to WT hMGLs.

“Interestingly, we did not observe a difference in internalization of oligomeric Aβ (Figure S4C), consistent with previous reports (Ovesen et al. 2024).”

• cites Ovesen et al. 2024 sourceNot checked yet

  Checked before — its earlier verdict is held back until a new check runs.

Depletion of SORL1 resulted in reduced lysosomal enzyme activity of HEXB, CTSD, and CTSB in SORL1 KO hMGLs relative to WT hMGLs.

“Depletion of SORL1 resulted in reduced lysosomal enzyme activity of HEXB, CTSD, and CTSB (Figure 2A–C) without altering protein expression in SORL1 KO hMGLs relative to WT hMGLs (Figure 2D–I).”

Both WT and SORL1 KO hMGLs show an increase in cell-surface localization of LAMP1 upon calcimycin treatment.

“Both WT and SORL1 KO hMGLs showed an increase in cell‐surface localization of LAMP1 upon calcimycin treatment, suggesting that hMGLs can undergo LE in vitro.”

SORL1 KO hMGLs show increased lysosomal accumulation of fibrillar Aβ 1-42, as evidenced by increased colocalization with LAMP1.

“Consistent with our hypothesis, SORL1 KO hMGLs showed increased accumulation of both substrates as evidenced by increased colocalization of Aβ 1–42 (Figure 5A,B) and synaptosomes (Figure 5C,D) with LAMP1.”

SORL1 KO hMGLs show no alteration of total protein levels of TREM2 and P2Y6 receptors compared to WT hMGLs.

“We observed increased surface localization of both receptors in SORL1 KO hMGLs (Figure S5A–D) without alteration of total protein levels of TREM2 and P2Y6 receptor (Figure S5E–F) suggesting that SORLA may play a role in maintaining the number of receptors at the cell surface required for phagocytosis, and its absence causes aberrant localization of these receptors.”

SORL1 KO hMGLs show a slight decrease in the levels of IL-6 released after calcimycin treatment.

“Interestingly, we saw a slight decrease in the levels of IL‐6 released after calcimycin treatment in SORL1 KO hMGLs (Figure 6F), suggesting that altered levels of LE in these cells may affect release of this cytokine.”

SORL1 KO hMGLs show reduced extracellular enzyme activity of HEXB, Cathepsin B, and Cathepsin D upon treatment with calcimycin.

“We found reduced extracellular enzyme activity of HEXB, Cathepsin B, and Cathepsin D (Figure 6D–F) and reduced protein levels of all three lysosomal enzymes in cell culture media (Figure S3A–D) in SORL1 KO hMGLs upon treatment with a LE activator, calcimycin.”

The decrease in surface LAMP1 localization in SORL1 KO hMGLs was not due to reduced total protein expression of LAMP1.

“This decrease was not due to the reduced total protein expression of LAMP1 (Figure 6C).”

SORL1 KO hMGLs had reduced colocalization of CIMPR with LAMP1 compared to WT hMGLs.

“Our data showed that SORL1 KO hMGLs had reduced colocalization of CIMPR with LAMP1 and no change in colocalization with TGN38 (Figure 4A,B), suggesting that the loss of SORL1 leads to an impaired CIMPR‐dependent trafficking pathway of lysosomal enzymes out of the TGN to lysosomes.”

SORL1 KO hMGLs show increased lysosomal accumulation of synaptosomes, as evidenced by increased colocalization with LAMP1.

“Consistent with our hypothesis, SORL1 KO hMGLs showed increased accumulation of both substrates as evidenced by increased colocalization of Aβ 1–42 (Figure 5A,B) and synaptosomes (Figure 5C,D) with LAMP1.”

SORL1 KO hMGLs exhibit reduced surface LAMP1 localization compared to WT in both stimulated and unstimulated conditions.

“However, SORL1 KO hMGLs exhibited reduced surface LAMP1 localization as compared to WT in both stimulated and unstimulated conditions, as evidenced by immunocytochemistry (Figure 6A) and flow cytometry (Figure 6B) showing that loss of SORL1 results in decreased LE in hMGLs.”

SORL1 KO hMGLs show increased uptake of transferrin conjugated to Alexa fluor 647 compared to WT hMGLs.

“We also tested uptake of a general endocytosis marker, transferrin conjugated to Alexa fluor 647, and also showed increased uptake of this substrate in SORL1 KO hMGLs (Figure S4B).”

Uptake of FITC-Dextran showed a similar trend in SORL1 KO hMGLs.

“we performed an uptake assay with a general pinocytosis marker, FITC‐Dextran, and observed a similar trend in SORL1 KO hMGLs (Figure S4A).”

SORL1 KO hMGLs show increased surface localization of TREM2 and P2Y6 receptors compared to WT hMGLs.

“We observed increased surface localization of both receptors in SORL1 KO hMGLs (Figure S5A–D) without alteration of total protein levels of TREM2 and P2Y6 receptor (Figure S5E–F) suggesting that SORLA may play a role in maintaining the number of receptors at the cell surface required for phagocytosis, and its absence causes aberrant localization of these receptors.”

SORL1 KO hMGLs show decreased colocalization of HEXB, Cathepsin B, and Cathepsin D with LAMP1 compared to WT hMGLs.

“Our results showed increased colocalization of all three enzymes with TGN38 (Figure 3A,C,E) and decreased colocalization with LAMP1 (Figure 3B,D,F) suggesting that the enzymes are not appropriately trafficked to lysosomes from the TGN.”

SORL1 KO hMGLs show increased colocalization of HEXB, Cathepsin B, and Cathepsin D with TGN38 compared to WT hMGLs.

“Our results showed increased colocalization of all three enzymes with TGN38 (Figure 3A,C,E) and decreased colocalization with LAMP1 (Figure 3B,D,F) suggesting that the enzymes are not appropriately trafficked to lysosomes from the TGN.”

SORL1 KO hMGLs had no change in colocalization of CIMPR with TGN38 compared to WT hMGLs.

“Our data showed that SORL1 KO hMGLs had reduced colocalization of CIMPR with LAMP1 and no change in colocalization with TGN38 (Figure 4A,B), suggesting that the loss of SORL1 leads to an impaired CIMPR‐dependent trafficking pathway of lysosomal enzymes out of the TGN to lysosomes.”

Using a second hMGL differentiation protocol, reduction in intracellular CTSD activity in SORL1 KO hMGLs was independently confirmed.

“Using these hMGLs, we independently confirmed reduction in intracellular CTSD activity (Figure S2B), validating our hypothesis that loss of SORL1 results in reduced lysosomal enzyme activity.”

In a second model of hMGLs, SORL1 KO hMGLs showed decreased extracellular enzyme activity of HEXB and Cathepsin D.

“SORL1 KO hMGLs showed decreased extracellular enzyme activity of both enzymes (Figure S2C,D), validating the idea that loss of SORL1 impairs LE in hMGLs irrespective of the method used to generate microglia from hiPSCs.”

SORL1 KO hMGLs have reduced protein levels of CIMPR compared to WT hMGLs.

“Additionally, we observed reduced protein levels of CIMPR in SORL1 KO hMGLs as compared to WT hMGLs by Western blot analysis (Figure 4C–D).”

SORL1 KO hMGLs show a larger decrease in the secretion and expression of IL-6 in response to LPS and IFNγ.

“While we noticed a slight but significant blunting of IL‐6 in response to calcimycin treatment, we also observed a larger decrease in the secretion and expression of IL‐6 in response to canonical stimuli, LPS and IFNγ (Figure 6H,I,K,L).”

Genetic, epidemiological, and functional studies have established SORL1 as a gene that increases the risk for AD.

“Genetic, epidemiological, and functional studies have now cumulatively and unequivocally established SORL1 as a gene that increases the risk for ad, highlighting aberrant endo‐lysosomal trafficking as an important pathway in ad pathogenesis (Holstege et al. 2017, 2023; Kunkle et al. 2017; Lambert et al. 2013; Rogaeva et al. 2007; Scheltens et al. 2021).”

• cites Holstege et al. 2017, 2023Not matched

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

• cites Kunkle et al. 2017 sourceNot checked yet

  Checked before — its earlier verdict is held back until a new check runs.

• cites Lambert et al. 2013Not matched

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

Loss of SORL1 did not alter differentiation of hiPSCs into HPCs and hMGLs.

“Loss of SORL1 did not alter differentiation of hiPSCs into HPCs and hMGLs (Figure S1).”

Loss of SORLA results in altered trafficking of lysosomal enzymes in hMGLs.

“In this study, we show that loss of SORLA results in decreased lysosomal degradation and lysosomal enzyme activity due to altered trafficking of lysosomal enzymes in hMGLs.”

• Also stated in: § Introduction · plain

  “We used quantitative flow cytometry, immunocytochemistry, and functional enzymatic and cellular assays to reveal that SORL1 KO hMGLs show decreased lysosomal degradation and reduced lysosomal enzymatic activity due to impaired trafficking of lysosomal enzymes from the trans‐Golgi network (TGN) to lysosomes.”

Abnormal lysosomes in microglia can negatively alter phagocytic and inflammatory responses, functions known to cause neuroinflammation in AD.

“Abnormal lysosomes in microglia can negatively alter phagocytic and inflammatory responses (Iyer et al. 2022; Lancaster et al. 2021; Quick et al. 2023; Ren et al. 2022), functions known to cause neuroinflammation in ad, substantiating the need to investigate microglia‐specific lysosomal pathways as therapeutic targets.”

• cites Iyer et al. 2022 sourceNot checked yet

  Checked before — its earlier verdict is held back until a new check runs.

• cites Lancaster et al. 2021 sourceNot checked yet
• cites Quick et al. 2023 sourceNot checked yet

Fibrillar amyloid beta 1-42 and synaptosomes aberrantly accumulate in lysosomes in SORLA-deficient hMGLs due to reduced lysosomal degradation.

“Phagocytic uptake of fibrillar amyloid beta 1–42 and synaptosomes is increased in SORLA‐deficient hMGLs, but due to reduced lysosomal degradation, these substrates aberrantly accumulate in lysosomes.”

Impaired lysosomal exocytosis may contribute to an altered immune response in SORL1-deficient microglia.

“An alternative mechanism of lysosome clearance, lysosomal exocytosis, is also impaired in SORL1‐deficient microglia, which may contribute to an altered immune response.”

SORL1 regulates lysosomal homeostasis in human microglia.

“Overall, our data show that SORL1 regulates lysosomal homeostasis in human microglia.”

The microglial endo-lysosomal network is a potential novel pathway through which SORL1 may increase AD risk and contribute to the development of AD.

“This further substantiates the microglial endo‐lysosomal network as a potential novel pathway through which SORL1 may increase ad risk and contribute to the development of ad.”

Loss of SORLA leads to enlarged lysosomes in hiPSC-derived microglia-like cells (hMGLs).

“Loss of SORLA leads to enlarged lysosomes in hiPSC‐derived microglia‐like cells (hMGLs).”

• Also stated in: § Introduction · plain

  “Our previous work has shown that loss of the intracellular sorting receptor and potent ad risk gene, Sortilin‐related receptor‐1 (SORL1), that encodes the multidomain protein SORLA, results in enlarged lysosomes in hMGLs (Mishra 2024).”

• cites Mishra 2024Not matched

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

Retromer and its receptors, SORLA and CIMPR, function to traffic mature lysosomal hydrolases from the TGN via endosomes to lysosomes.

“In particular, retromer and its receptors, SORLA and the cation‐independent mannose‐6 phosphate receptor (CIMPR), function to traffic mature lysosomal hydrolases from the TGN via endosomes to lysosomes (Cui et al. 2019; Hasanagic et al. 2015; Nielsen et al. 2007).”

• cites Cui et al. 2019Not matched

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

• cites Hasanagic et al. 2015 sourceNot checked — no full text of the source
• cites Nielsen et al. 2007 sourceNot checked — no full text of the source

Here we provide evidence for the role of SORLA in regulating lysosome function in human microglia.

“Here we provide evidence for the role of SORLA in regulating lysosome function in human microglia.”

Loss of SORL1 leads to decreased lysosomal enzyme activity.

“Loss of SORL1 (orange circle) leads to decreased lysosomal degradation and decreased lysosomal enzyme activity caused by impaired trafficking of CIMPR and lysosomal enzymes from the TGN.”

Lysosomal accumulation of substrates including fibrillar Aβ 1-42 and synaptosomes occurs due to decreased degradative capacity of lysosomes upon loss of SORL1.

“Loss of SORL1 also causes enhanced phagocytic uptake due to increased cell surface localization of phagocytic receptors, but due to the decreased degradative capacity of the lysosomes, there is lysosomal accumulation of substrates including fibrillar Aβ 1–42 and synaptosomes.”

The decrease in pro-inflammatory cytokine release upon SORL1 depletion may occur by impairing lysosomal exocytosis.

“Furthermore, the depletion of SORL1 may decrease the release of pro‐inflammatory cytokines either through conventional secretory routes from the TGN to the cell surface or by impairing LE, as observed in our study and others (Ovesen et al. 2024).”

SORL1 regulates the endo-lysosomal pathway in a cell-type-specific mechanism beyond its well-established function as a sorting receptor for APP in neurons.

“Our data identify a previously unexplored cell‐type‐specific mechanism through which SORL1 can regulate the endo‐lysosomal pathway beyond its well‐established function as a sorting receptor for APP in neurons, illustrating the importance of exploring this multifaceted sorting receptor and potent ad risk factor as a therapeutic target for ad.”

Hypofunctional microglia with depleted SORLA may initially contribute to AD pathogenesis through lysosome dysfunction.

“Since the loss of SORL1 is observed in the early stages of ad, hypofunctional microglia with depleted SORLA may initially contribute to ad pathogenesis through lysosome dysfunction.”

• AssumptionRests on an assumption: Loss of SORL1 is observed in the early stages of AD.

SORL1 KO hMGLs have reduced lysosomal degradation of DQ-Red-BSA rather than reduced uptake of DQ-BSA.

“Together, this data suggest that SORL1 KO hMGLs have reduced lysosomal degradation of DQ‐Red‐BSA rather than reduced uptake of DQ‐BSA.”

Loss of SORL1 leads to an impaired CIMPR-dependent trafficking pathway of lysosomal enzymes out of the TGN to lysosomes.

“suggesting that the loss of SORL1 leads to an impaired CIMPR‐dependent trafficking pathway of lysosomal enzymes out of the TGN to lysosomes.”

Important components of LE are impaired in SORL1 KO hMGLs.

“While the reduction in extracellular enzyme activity and protein is likely due to the altered trafficking of hydrolases, taken together along with the reduction in cell surface LAMP1 localization, this strongly indicates that important components of LE are impaired in SORL1 KO hMGLs.”

Lysosomal phenotypes due to SORL1 deficiency are not due to differences between in vitro differentiation protocols.

“Furthermore, lysosomal phenotypes due to SORL1 deficiency are not due to differences between in vitro differentiation protocols.”

Loss of SORL1 expression may change localization of phagocytic receptors and genes involved in phagocytosis of specific substrates.

“Together, this data suggests that loss of SORL1 expression may change localization of phagocytic receptors and genes involved in phagocytosis of specific substrates.”

The increased accumulation of substrates in lysosomes may also indicate a failure to release these substrates via LE.

“Thus, the increased accumulation of substrates in lysosomes may also indicate a failure to release these substrates via LE.”

In our hMGLs, SORLA may increase phagocytosis of fibrillar Aβ and synaptosomes by increasing surface localization of phagocytic receptors, TREM2 and P2Y6.

“Overall, these data suggest that, in our hMGLs, SORLA may increase phagocytosis of fibrillar Aβ and synaptosomes by increasing surface localization of phagocytic receptors, TREM2 and P2Y6, in hMGLs.”

In vitro studies using hiPSC-derived microglia do not allow thorough representation of cellular complexity characteristics of the physiological brain environment.

“In vitro studies using hiPSC‐derived microglia do not allow thorough representation of cellular complexity characteristics of the physiological brain environment.”

Alternate pathways to release lysosomal cargo from cells, such as LE, are also impaired in SORL1 KO hMGLs.

“Alternate pathways to release lysosomal cargo from cells, such as LE, are also impaired.”

This impairment contributes to a blunted neuroimmune response.

“This impairment contributes to a blunted neuroimmune response.”

Lysosome dysfunction in microglia is a pathway through which SORL1 loss of function may increase risk for AD.

“In summary, our study highlights lysosome dysfunction in microglia as a pathway through which SORL1 loss of function may increase the risk for ad.”

• AssumptionRests on an assumption: SORL1 is a potent AD risk factor.

Enhanced phagocytic uptake upon loss of SORL1 is due to increased cell surface localization of phagocytic receptors.

“Loss of SORL1 also causes enhanced phagocytic uptake due to increased cell surface localization of phagocytic receptors, but due to the decreased degradative capacity of the lysosomes, there is lysosomal accumulation of substrates including fibrillar Aβ 1–42 and synaptosomes.”

Loss of SORL1 leads to inefficient degradation of phagocytosed substrates.

“Loss of SORL1 impairs the trafficking of lysosomal enzymes from the TGN to the lysosome via the M6P pathway, leading to inefficient degradation of phagocytosed substrates that accumulate in lysosomes.”

Loss of SORL1 results in decreased LE in hMGLs.

“showing that loss of SORL1 results in decreased LE in hMGLs.”

Decreased lysosomal enzyme activity, rather than changes in overall lysosomal protein expression, contributes to the reduction in lysosomal degradation observed in SORL1 KO hMGLs.

“Overall, our data suggest that decreased lysosomal enzyme activity, rather than changes in overall lysosomal protein expression, contributes to the reduction in lysosomal degradation observed in SORL1 KO hMGLs.”

In the context of AD, lysosome dysfunction in microglia caused by loss of SORL1 may result in heightened lysosomal stress.

“In the context of ad, we posit that lysosome dysfunction in microglia caused by the loss of SORL1 may result in heightened lysosomal stress caused by increased accumulation of substrates and a stunted inflammatory response to accumulating pathogenic proteins in the extracellular brain environment.”

• Also stated in: § Working Model · plain

  “Altogether, loss of SORL1 causes increased lysosomal stress in human microglia.”

Characterization of hMGLs generated using a different protocol showed no difference in expression of microglia-specific markers between WT and SORL1 KO cells.

“Characterization of these hMGLs showed no difference in expression of microglia‐specific markers between WT and SORL1 KO cells (Figure S2A).”

Impaired degradation in SORLA deficient hMGLs affects the fate of phagocytosed substrates.

“Impaired degradation in SORLA deficient hMGLs affects the fate of phagocytosed substrates.”

Alternate pathways of lysosomal clearance, such as lysosomal exocytosis, are impaired upon loss of SORL1.

“Alternate pathways of lysosomal clearance, such as LE, are also impaired.”

• Also stated in: § Working Model · plain

  “Alternate pathways of lysosomal clearance such as lysosomal exocytosis are also impaired, contributing to a blunted neuroimmune response.”

Loss of SORL1 impairs the trafficking of lysosomal enzymes from the TGN to the lysosome via the M6P pathway.

“Loss of SORL1 impairs the trafficking of lysosomal enzymes from the TGN to the lysosome via the M6P pathway, leading to inefficient degradation of phagocytosed substrates that accumulate in lysosomes.”

Dysfunction in lysosomal degradation in SORL1 KO hMGLs is likely due to mistrafficking of lysosomal enzymes.

“As we observed decreased enzyme activity but no change in total protein expression of CTSD, CTSB, and HEXB, our data suggested that dysfunction in lysosomal degradation is likely due to mistrafficking of lysosomal enzymes.”

Through increased phagocytic uptake combined with impaired lysosomal degradation, loss of SORL1 significantly increases lysosomal dysfunction in human microglia.

“Together, our data demonstrate that through increased phagocytic uptake combined with impaired lysosomal degradation, loss of SORL1 significantly increases lysosomal dysfunction in human microglia.”

Altered levels of LE in SORL1 KO hMGLs may affect release of IL-6.

“suggesting that altered levels of LE in these cells may affect release of this cytokine.”

hMGLs can undergo LE in vitro.

“suggesting that hMGLs can undergo LE in vitro.”

We have documented lysosomal enlargement in SORL1 KO microglia.

“We did not observe differences in the size of early endosomes between SORL1 WT and SORL1 KO hMGLs (Knupp et al. 2020) but have documented lysosomal enlargement in SORL1 KO microglia (Mishra 2024).”

• cites Mishra 2024Not matched

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

Loss of SORL1 causes enhanced phagocytic uptake.

“Loss of SORL1 also causes enhanced phagocytic uptake due to increased cell surface localization of phagocytic receptors, but due to the decreased degradative capacity of the lysosomes, there is lysosomal accumulation of substrates including fibrillar Aβ 1–42 and synaptosomes.”

Chloroquine treatment caused a significant increase in lysosomal accumulation of fAβ and synaptosomes in both WT and SORL1 KO hMGLs.

“As expected, chloroquine treatment caused a significant increase in lysosomal accumulation of both substrates in both WT and SORL1 KO hMGLs (Figure 5B,D).”

Phagocytosed substrates accumulate in lysosomes upon loss of SORL1.

“Loss of SORL1 impairs the trafficking of lysosomal enzymes from the TGN to the lysosome via the M6P pathway, leading to inefficient degradation of phagocytosed substrates that accumulate in lysosomes.”

• Also stated in: § Working Model · plain

  “Loss of SORL1 also causes enhanced phagocytic uptake due to increased cell surface localization of phagocytic receptors, but due to the decreased degradative capacity of the lysosomes, there is lysosomal accumulation of substrates including fibrillar Aβ 1–42 and synaptosomes.”

In the context of AD, lysosome dysfunction in microglia caused by loss of SORL1 may result in a stunted inflammatory response to accumulating pathogenic proteins in the extracellular brain environment.

“In the context of ad, we posit that lysosome dysfunction in microglia caused by the loss of SORL1 may result in heightened lysosomal stress caused by increased accumulation of substrates and a stunted inflammatory response to accumulating pathogenic proteins in the extracellular brain environment.”

Calcimycin increases secretion of cytokines by increasing LE rather than by activating microglia.

“These data suggest that calcimycin increases secretion of cytokines by increasing LE rather than by activating microglia.”

Multiple mechanisms may govern SORLA-mediated cytokine release in hMGLs.

“We also observed a blunted cytokine release in response to canonical pro‐inflammatory stimuli, LPS, and IFNγ, consistent with other recent reports in SORLA‐deficient hMGLs (Ovesen et al. 2024), suggesting that multiple mechanisms may govern SORLA‐mediated cytokine release in hMGLs.”

• cites Ovesen et al. 2024 sourceNot checked yet

  Checked before — its earlier verdict is held back until a new check runs.

Lysosomal enzymes are not appropriately trafficked to lysosomes from the TGN in SORL1 KO hMGLs.

“suggesting that the enzymes are not appropriately trafficked to lysosomes from the TGN.”

Loss of SORL1 impairs LE in hMGLs irrespective of the method used to generate microglia from hiPSCs.

“validating the idea that loss of SORL1 impairs LE in hMGLs irrespective of the method used to generate microglia from hiPSCs.”