Cited by 191Amyotrophic Lateral Sclerosis ResearchAutophagy in Disease and TherapyAlzheimer's disease research and treatments

The DOI matches its Crossref record; 526 of the 527 references it cites were found in a registry or an index; 29 of the 524 sources its claims cite were checked for support.

Autophagy and ALS: mechanistic insights and therapeutic implications

Open access
Chua, Jason P., De Calbiac, Hortense, Kabashi, Edor, Barmada, Sami J.·2022·Autophagy

Abstract

: ALS: amyotrophic lateral sclerosis; Atg: autophagy-related; CHMP2B: charged multivesicular body protein 2B; DPR: dipeptide repeat; FTD: frontotemporal dementia; iPSC: induced pluripotent stem cell; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; PINK1: PTEN induced kinase 1; RNP: ribonuclear protein; sALS: sporadic ALS; SPHK1: sphingosine kinase 1; TARDBP/TDP-43: TAR DNA binding protein; TBK1: TANK-binding kinase 1; TFEB: transcription factor EB; ULK: unc-51 like autophagy activating kinase; UPR: unfolded protein response; UPS: ubiquitin-proteasome system; VCP: valosin containing protein.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This review synthesizes mechanistic links between autophagy dysfunction and ALS, focusing on ALS-associated mutations in autophagy-related genes and cell type-specific regulation of autophagy. It argues that effective autophagy-based therapies will require targeting the pathway in specific cell types rather than indiscriminate induction.

Key findings

  • ALS-related mutations affect multiple autophagy stages and factors, including SQSTM1, C9orf72, TBK1, UBQLN2, FUS, VCP, OPTN, and CHMP2B; these mutations impair selective autophagy, mitophagy, autophagosome maturation, or autophagic flux.
  • Reported mutation frequencies include C9orf72 expansion in 23–47% of familial ALS/FTD and 4–21% of sporadic disease; TBK1 mutations in ~1% of familial or sporadic ALS; OPTN mutations in ~3% of familial and ~1% of sporadic ALS; VCP mutations in ~1–2% of familial ALS; and SQSTM1 mutations in ~1–3.5% of ALS-FTD cases.
  • Autophagy regulation differs by cell type: neurons are insensitive or only mildly responsive to starvation and MTOR inhibition, whereas astrocytes, oligodendrocytes, Schwann cells, and skeletal muscle respond to these stimuli; neuronal autophagy can be induced by MTOR/AKT-independent compounds such as 10-NCP.
  • Therapeutic implications are mixed: rapamycin can worsen disease in SOD1G93A ALS mice, lithium showed no clinical benefit in five ALS trials, and a phase II rapamycin trial in ALS began in 2018 with results not yet published.

Methods

  • Narrative review of the autophagy pathway, ALS-associated autophagy-related mutations, disease models, and cell type-specific autophagy regulation.
  • No primary experimental design, sample, or statistical analysis is reported; the paper synthesizes published cell, animal, iPSC, and human data.
  • Main analysis is conceptual integration of mechanistic findings to identify therapeutic targets and remaining questions.

Limitations

  • The authors state that mechanistic details of autophagy’s neuroprotective role, neuronal resistance to autophagy induction, neuron-specific effects of autophagy-impairing mutations, and non-cell autonomous contributions to ALS pathogenesis remain incompletely defined.
  • The authors note that cell type-specific autophagy regulation is insufficiently explored, that cell and animal models may not faithfully reproduce human autophagy regulation, and that LC3-II accumulation cannot distinguish true autophagy induction from late-stage inhibition.
  • Evident from the text: this is a review without a systematic search strategy or primary data, and it relies on model systems that may not fully translate to human disease.

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

Integrity signals

Registry

Crossref · 10.1080/15548627.2021.1926656

Cites

526 of 526 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Figures

Figure 1. Dysfunction of autophagy-related proteins impairs proteostasis and leads to neurotoxicity in ALS. (A) Under normal conditions, SQSTM1 serves as a receptor protein in selective autophagy and binds both LC3-II and polyubiquitinated proteins, thereby targeting ubiquitinated substrates to phagophores (left); Mutations in SQSTM1 abrogate SQSTM1’s binding activities (right top) or result in the aggregation of SQSTM1 into ubiquitin-positive inclusions (right bottom). (B) The C9orf72 protein participates in several autophagy-related complexes, including the autophagy induction complex (ULK1-RAB1A) that promotes autophagosome biogenesis, the RAB7-RAB11 complex (RAB complex) that regulates endosome maturation, and the C9orf72-SMCR8-WDR41 (CSW) complex that regulates lysosomal dynamics and autophagic flux (left). Disease-associated C9orf72 mutations reduce C9orf72 protein levels (right), while dipeptide repeat proteins generated from the C9orf72 expansion localize to SQSTM1- and ubiquitin-positive inclusions (right). (C) In normal mitophagy, TBK1 binds and phosphorylates OPTN, enhancing its affinity for polyubiquitinated mitochondria and LC3-II (left). TBK1 and OPTN mutations perturb these functions and compromise efficient mitophagy, leading to failed mitochondrial clearance and dysfunctional mitochondria.
Figure 1. Dysfunction of autophagy-related proteins impairs proteostasis and leads to neurotoxicity in ALS. (A) Under normal conditions, SQSTM1 serves as a receptor protein in selective autophagy and binds both LC3-II and polyubiquitinated proteins, thereby targeting ubiquitinated substrates to phagophores (left); Mutations in SQSTM1 abrogate SQSTM1’s binding activities (right top) or result in the aggregation of SQSTM1 into ubiquitin-positive inclusions (right bottom). (B) The C9orf72 protein participates in several autophagy-related complexes, including the autophagy induction complex (ULK1-RAB1A) that promotes autophagosome biogenesis, the RAB7-RAB11 complex (RAB complex) that regulates endosome maturation, and the C9orf72-SMCR8-WDR41 (CSW) complex that regulates lysosomal dynamics and autophagic flux (left). Disease-associated C9orf72 mutations reduce C9orf72 protein levels (right), while dipeptide repeat proteins generated from the C9orf72 expansion localize to SQSTM1- and ubiquitin-positive inclusions (right). (C) In normal mitophagy, TBK1 binds and phosphorylates OPTN, enhancing its affinity for polyubiquitinated mitochondria and LC3-II (left). TBK1 and OPTN mutations perturb these functions and compromise efficient mitophagy, leading to failed mitochondrial clearance and dysfunctional mitochondria.CC BY-NC-ND · PubMed Central
Figure 2. Distinct factors regulate autophagy among different cell types of the nervous system. In each of the cells which comprise the central and peripheral nervous systems, autophagy is differentially regulated by cell type-specific effectors. In neurons (top left), modulation of SPHK1 by phenoxazine compounds such as 10-NCP, but not starvation, potently induces autophagy. In contrast, nutrient deprivation is sufficient to promote SPHK1 signaling and autophagy induction in astrocytes (top center). In the axonal compartment of neurons, KIF1A and PINK1-PRKN are critical for facilitating local autophagic activity (left, middle). MicroRNAs such as MIR101 and MIR195 suppress oligodendrocytic and Schwann cell autophagy, respectively (right). Schwann cells also clear myelin debris through myelinophagy, a unique form of selective autophagy that is dependent on FIG4 (bottom). In muscle, specific transcription factors can exert activating (FOXO3) or suppressive (PPARGC1A, RUNX1) effects on autophagy, and phosphatases such as MTM1 and MTMR14 inhibit autophagy by recycling phosphoinositides needed for autophagy induction (bottom left).
Figure 2. Distinct factors regulate autophagy among different cell types of the nervous system. In each of the cells which comprise the central and peripheral nervous systems, autophagy is differentially regulated by cell type-specific effectors. In neurons (top left), modulation of SPHK1 by phenoxazine compounds such as 10-NCP, but not starvation, potently induces autophagy. In contrast, nutrient deprivation is sufficient to promote SPHK1 signaling and autophagy induction in astrocytes (top center). In the axonal compartment of neurons, KIF1A and PINK1-PRKN are critical for facilitating local autophagic activity (left, middle). MicroRNAs such as MIR101 and MIR195 suppress oligodendrocytic and Schwann cell autophagy, respectively (right). Schwann cells also clear myelin debris through myelinophagy, a unique form of selective autophagy that is dependent on FIG4 (bottom). In muscle, specific transcription factors can exert activating (FOXO3) or suppressive (PPARGC1A, RUNX1) effects on autophagy, and phosphatases such as MTM1 and MTMR14 inhibit autophagy by recycling phosphoinositides needed for autophagy induction (bottom left).CC BY-NC-ND · PubMed Central
Figure 3. Mechanisms of neuronal autophagy and their impact for therapeutic design in ALS. Pharmacodynamic considerations limit the use of currently available drugs for modulating autophagy. Inhibitors of MTOR inhibitors (rapalogs) only weakly activate autophagy in neurons, and their wide-ranging effects target myriad cellular pathways, including growth signaling, translation, stress responses, transcriptional regulation, and cytoskeletal remodeling (left). Such pleiotropy leads to well-documented and multi-systemic toxicities, especially with long-term use; however, newer rapalogs may enable more specific targeting and selective autophagy modulation. Similarly, lithium has numerous multi-target effects, including depletion of IP3 through IMPase, activating nitric oxide synthase, inhibiting GSK3B, stimulating NMDA receptors and enhancing glutamatergic tone, among many others (middle). This results in a narrow therapeutic index for lithium, potentially explaining its apparent lack of neuroprotective effects in human trials for neurodegenerative disease to date. To reduce off-target effects, recent efforts have focused on MTOR-independent strategies for stimulating autophagy, including modulation of SIRT1, phenoxazine compounds such as 10-NCP, or synthetic peptides such as Tat-Beclin 1 (right).
Figure 3. Mechanisms of neuronal autophagy and their impact for therapeutic design in ALS. Pharmacodynamic considerations limit the use of currently available drugs for modulating autophagy. Inhibitors of MTOR inhibitors (rapalogs) only weakly activate autophagy in neurons, and their wide-ranging effects target myriad cellular pathways, including growth signaling, translation, stress responses, transcriptional regulation, and cytoskeletal remodeling (left). Such pleiotropy leads to well-documented and multi-systemic toxicities, especially with long-term use; however, newer rapalogs may enable more specific targeting and selective autophagy modulation. Similarly, lithium has numerous multi-target effects, including depletion of IP3 through IMPase, activating nitric oxide synthase, inhibiting GSK3B, stimulating NMDA receptors and enhancing glutamatergic tone, among many others (middle). This results in a narrow therapeutic index for lithium, potentially explaining its apparent lack of neuroprotective effects in human trials for neurodegenerative disease to date. To reduce off-target effects, recent efforts have focused on MTOR-independent strategies for stimulating autophagy, including modulation of SIRT1, phenoxazine compounds such as 10-NCP, or synthetic peptides such as Tat-Beclin 1 (right).CC BY-NC-ND · PubMed Central

Verification

Claims the paper makes

264 Not checked yet · 25 Own interpretation · 7 No basis given · 5 Partly supported · 3 Supported · 3 Supported so far · 3 Mixed support · accuracy not yet measured

Verify all 495 references — free account

Show all 166 claims

  • Probably not a substantial claim. 31
  • It may state two separate claims as one. 127
144 of 144
  • The paper relies on this without support.

    Findings from animal and cell models of ALS (e.g., mouse, zebrafish, iPSC) are relevant to human ALS pathogenesis.

    “These results are consistent with those in animal models, suggesting that the endogenously encoded C9orf72 repeat expansion mutation leads to toxicity by both gain and loss of function mechanisms.”
  • The authors state this as an assumption.

    c9orf72 knockout in mouse models the loss of function attributed to the C9orf72 hexanucleotide repeat expansion.

    “Paradoxically, however, c9orf72 knockout in mouse (which models the loss of function attributed to the hexanucleotide repeat expansion) enhances autophagy by de-repressing MTOR and, in turn, increasing TFEB nuclear translocation [179,180].”
  • The paper relies on this without support.

    Autophagy-based therapies can be effective for ALS and related neurodegenerative diseases.

    “This review thereby provides a framework not only to guide further investigations of neuronal autophagy but also to refine therapeutic strategies for ALS and related neurodegenerative diseases.”
3 of 3

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Citations

Cites

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Research works printed but not linked: 10

  1. Laferriere F, 2015, Swiss Med Wkly, 145, w14054
  2. Le Ber I, 2013, JAMA Neurol, 70, 1403
  3. Anor CJ, 2015, Neurobiol Aging, 36
  4. Komine O, 2015, Nagoya J Med Sci, 77, 537
  5. Arenas A, 2020, J Neurochem
  6. Clayton EL, 2017, Hum Mol Genet, 26, 873
  7. Chen Y, 2015, Am J Transl Res, 7, 1574
  8. Miller RH, 1994, Perspect Dev Neurobiol, 2, 225
  9. Kulkarni A, 2019, Autophagy.
  10. Nguyen LS, 2019, Drug Saf, 42, 813

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Metadata

Authors
Chua, J. P., De Calbiac, H., Kabashi, E., & Barmada, S. J.
Affiliations
  • University of Michigan (US)
  • Recherche translationnelle sur les maladies neurologiques, Institut Imagine, UMR-1163 INSERM et Université Paris Descartes, Hôpital Universitaire Necker-Enfants Malades, Paris, France
  • Hôpital Necker-Enfants Malades (FR)
Corresponding author
Barmada, Sami J.
Venue
Autophagy
Published
2021-05-31
Volume
18
Issue
2
Pages
254-282
ISSN
  • 1554-8627 (ISSN-L)
  • 1554-8635
OpenAlex
W3164735937
Cited by
189
References
527
Citations by year
2026: 34 · 2025: 51 · 2024: 46 · 2023: 34 · 2022: 19 · 2021: 5
FWCI
3.39
Type
journal article
Language
en
Open access
Locations
  • Autophagy (publishedVersion, cc-by-nc-nd)
  • PubMed Central (publishedVersion, cc-by-nc-nd)
  • PubMed (publishedVersion)
Funders
National Institute of Neurological Disorders and Stroke (2R25NS089450-06)
Topics
  • Health Sciences › Medicine › Clinical Neurology › Amyotrophic Lateral Sclerosis Research
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Autophagy in Disease and Therapy
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Alzheimer's disease research and treatments
Keywords
amyotrophic lateral sclerosis, CHMP2B, dipeptide repeat proteins, PINK1, mTOR, TBK1, TFEB, LC3, VCP, ubiquitin-proteasome system, unfolded protein response, frontotemporal dementia, autophagy-related proteins, therapeutic target
MeSH terms
Proteostasis, Amyotrophic Lateral Sclerosis, Autophagy, Humans, Unfolded Protein Response, Frontotemporal Dementia

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