epg-5

UniProt ID: Q18892
Organism: Caenorhabditis elegans
Review Status: COMPLETE
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Gene Description

EPG-5 (Ectopic P granules protein 5) is a metazoan-specific autophagy tethering factor that functions as a RAB-7 effector to determine the fusion specificity of autophagosomes with late endosomes/lysosomes. EPG-5 binds RAB-7 on late endosomes/lysosomes and engages LGG-1 (C. elegans LC3/ATG8 ortholog) via conserved LIR motifs on autophagosomes. It coordinates the STX17-SNAP29-VAMP7/8 trans-SNARE machinery to promote correct autophagosome-lysosome fusion and prevent aberrant SNARE pairing. Loss of epg-5 causes accumulation of non-degradative hybrid vesicles bearing both autophagosomal and endosomal markers, impaired lysosomal acidification, and defective autophagy flux. EPG-5 also functions in LAP (LC3-associated phagocytosis) to promote delivery of engulfed apoptotic cells to lysosomes. Human ortholog EPG5 mutations cause Vici syndrome, a severe multisystem disorder.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0005737 cytoplasm
IBA
GO_REF:0000033
ACCEPT
Summary: EPG-5 is localized to the cytoplasm with partial localization to late endosome/lysosome membranes and autophagosome-lysosome contact sites. The IBA annotation is consistent with the general cytoplasmic distribution of this protein.
Reason: EPG-5 is a cytoplasmic protein that is recruited to late endosomes/lysosomes via RAB-7 interaction. The cytoplasm annotation accurately reflects the general localization of EPG-5 before it is recruited to specific membrane compartments for its fusion-tethering function.
Supporting Evidence:
PMID:22451698
The EPG-5 protein was reported to evenly distribute in the cytosol
file:worm/epg-5/epg-5-deep-research-falcon.md
EPG-5 is predominantly cytoplasmic and recruited to autophagosomes
GO:0097352 autophagosome maturation
IBA
GO_REF:0000033
ACCEPT
Summary: EPG-5 is essential for autophagosome maturation, functioning as a RAB-7 effector that determines fusion specificity of autophagosomes with late endosomes/lysosomes. This is a core function of the protein conserved across metazoans.
Reason: Autophagosome maturation is a core function of EPG-5. The protein acts as a tethering factor that binds RAB-7 on late endosomes/lysosomes and LGG-1 on autophagosomes, coordinating SNARE-mediated fusion. epg-5 mutants accumulate non-degradative autolysosomes indicating impaired maturation.
Supporting Evidence:
PMID:20550938
EI24 and mEPG5 are required for formation of degradative autolysosomes
PMID:24374177
LGG-2 controls the maturation of LGG-1-positive autophagosomes and facilitates the tethering with the lysosomes
GO:0005737 cytoplasm
IEA
GO_REF:0000044
ACCEPT
Summary: IEA annotation based on UniProt subcellular location vocabulary mapping. Consistent with IBA annotation and experimental evidence.
Reason: This annotation is correct and consistent with the IBA annotation and experimental evidence. It is acceptable to retain both IBA and IEA annotations for the same term.
Supporting Evidence:
PMID:22451698
The EPG-5 protein was reported to evenly distribute in the cytosol
GO:0006914 autophagy
IEA
GO_REF:0000043
ACCEPT
Summary: EPG-5 is involved in autophagy, specifically in the late autophagosome maturation/fusion step. This IEA annotation from UniProt keyword mapping is correct but more general than the specific function (autophagosome maturation).
Reason: While GO:0097352 (autophagosome maturation) is more specific for EPG-5's function, the parent term GO:0006914 (autophagy) is not incorrect. The IEA annotation provides a valid broader annotation that complements the more specific IBA annotation.
Supporting Evidence:
PMID:20550938
EI24 and mEPG5 are required for formation of degradative autolysosomes
GO:0030670 phagocytic vesicle membrane
IEA
GO_REF:0000044
ACCEPT
Summary: EPG-5 localizes to phagosome membranes of engulfed apoptotic cells during LAP (LC3-associated phagocytosis). This is supported by experimental evidence in PMID:22451698.
Reason: EPG-5::GFP was recruited to the outer surface of internalized apoptotic Q cell corpses in the phagocyte. This localization is distinct from its role in canonical autophagy but represents a genuine function in apoptotic cell clearance via LAP.
Supporting Evidence:
PMID:22451698
the autophagy proteins LGG-1, ATG-18, and EPG-5 are recruited from the phagocyte to the outer surface of internalized Q cell corpses
GO:0031410 cytoplasmic vesicle
IEA
GO_REF:0000043
ACCEPT
Summary: EPG-5 localizes to cytoplasmic vesicles including late endosomes/lysosomes and autophagosomes. This annotation is supported by experimental localization data.
Reason: EPG-5 localizes to late endosomes/lysosomes via RAB-7 interaction and to sites of autophagosome-lysosome contact.
Supporting Evidence:
PMID:22451698
EPG-5::GFP was recruited on the Q cell corpse
file:worm/epg-5/epg-5-deep-research-falcon.md
EPG-5 localizes to autophagosomes and late endosomes/lysosomes
GO:1902902 negative regulation of autophagosome assembly
IMP
PMID:24374177
The C. elegans LC3 acts downstream of GABARAP to degrade aut...
MODIFY
Summary: This annotation suggests EPG-5 negatively regulates autophagosome assembly. However, EPG-5 functions at the autophagosome maturation step, not assembly. The observed increase in autophagosomes in epg-5 mutants is due to blocked fusion/degradation, not increased assembly rate.
Reason: The annotation appears to be based on the observation that epg-5 mutants cause accumulation of autophagosomes. However, this accumulation results from impaired autophagosome-lysosome fusion and degradation, not from increased autophagosome formation. EPG-5 acts downstream at the maturation step. The correct interpretation is that EPG-5 is involved in autophagosome maturation (GO:0097352) or autophagosome-lysosome fusion (GO:0061909). The term GO:1902902 misrepresents the mechanism.
Supporting Evidence:
PMID:24374177
LGG-2 controls the maturation of LGG-1-positive autophagosomes and facilitates the tethering with the lysosomes
PMID:20550938
EI24 and mEPG5 are required for formation of degradative autolysosomes
GO:0016236 macroautophagy
IMP
PMID:20550938
C. elegans screen identifies autophagy genes specific to mul...
ACCEPT
Summary: EPG-5 is essential for macroautophagy, specifically the maturation step where autophagosomes fuse with lysosomes. This is a core function supported by the seminal study that identified epg-5.
Reason: PMID:20550938 identified epg-5 in a genetic screen for autophagy genes and demonstrated that it is required for starvation-induced autophagy. While autophagosome maturation is the more specific step, macroautophagy accurately describes the broader process in which EPG-5 functions.
Supporting Evidence:
PMID:20550938
EI24 and mEPG5 are required for formation of degradative autolysosomes
GO:0005737 cytoplasm
IDA
PMID:20550938
C. elegans screen identifies autophagy genes specific to mul...
ACCEPT
Summary: Direct experimental evidence shows EPG-5 localizes to the cytoplasm.
Reason: This IDA annotation provides the strongest evidence for cytoplasmic localization. EPG-5 is a cytoplasmic protein that is recruited to late endosome/lysosome membranes for its fusion function.
Supporting Evidence:
PMID:22451698
The EPG-5 protein was reported to evenly distribute in the cytosol
GO:0061909 autophagosome-lysosome fusion
IMP
PMID:20550938
C. elegans screen identifies autophagy genes specific to mul...
NEW
Summary: EPG-5 is a tethering factor that directly promotes autophagosome-lysosome fusion by coordinating RAB-7, LGG-1/LC3, and SNARE proteins. This is the most specific term for EPG-5's core molecular function.
Reason: PMID:20550938 demonstrated that EPG-5 is required for formation of degradative autolysosomes. Later work definitively established that EPG-5 is a Rab7 effector that determines the fusion specificity of autophagosomes with late endosomes/lysosomes. This term should be added with IMP evidence.
Supporting Evidence:
PMID:20550938
EI24 and mEPG5 are required for formation of degradative autolysosomes
file:worm/epg-5/epg-5-deep-research-falcon.md
EPG-5 promotes autophagosome-lysosome fusion
GO:0031902 late endosome membrane
IDA
PMID:22451698
Autophagy genes function sequentially to promote apoptotic c...
NEW
Summary: EPG-5 localizes to late endosome/lysosome membranes via RAB-7 binding. This localization is essential for its tethering function.
Reason: EPG-5 is recruited to late endosomes/lysosomes via its interaction with RAB-7. This localization is distinct from the general cytoplasm annotation and more accurately reflects the site of EPG-5's action.
Supporting Evidence:
PMID:22451698
EPG-5::GFP was recruited on the Q cell corpse
file:worm/epg-5/epg-5-deep-research-falcon.md
EPG-5 localizes to late endosomes/lysosomes via RAB-7
GO:0000149 SNARE binding
IPI
PMID:20550938
C. elegans screen identifies autophagy genes specific to mul...
NEW
Summary: EPG-5 binds SNARE proteins to coordinate autophagosome-lysosome fusion. This molecular function annotation would complement the biological process annotations.
Reason: EPG-5 engages the autophagosomal Qabc SNARE complex STX17-SNAP29 and coordinates with the R-SNARE VAMP7/8 on late endosomes/lysosomes. SNARE binding is a core molecular function that enables EPG-5's tethering activity.
Supporting Evidence:
PMID:20550938
EI24 and mEPG5 are required for formation of degradative autolysosomes
file:worm/epg-5/epg-5-deep-research-falcon.md
EPG-5 coordinates SNARE complex assembly
GO:0031267 small GTPase binding
IPI
PMID:22451698
Autophagy genes function sequentially to promote apoptotic c...
NEW
Summary: EPG-5 is a RAB-7 effector that directly binds RAB-7. This molecular function is central to its role in autophagosome maturation.
Reason: EPG-5 binds RAB-7 (a small GTPase of the Rab family) on late endosomes/lysosomes. This interaction is essential for EPG-5 localization and function. RAB-7 binding is a core molecular function of EPG-5.
Supporting Evidence:
PMID:22451698
We found that the recruitment of RAB-7 onto the phagosome was delayed from 70 ± 15 min in WT (n = 11) to 145 ± 66 min in atg-18 (n = 18) and 102 ± 30 min in epg-5 (n = 12) mutants
file:worm/epg-5/epg-5-deep-research-falcon.md
EPG-5 is a RAB-7 effector

Core Functions

EPG-5 is a RAB-7 effector that directly binds RAB-7 GTPase on late endosomes/lysosomes. This interaction is essential for EPG-5 localization and function in autophagosome-lysosome tethering.

Supporting Evidence:
  • PMID:22451698
    We found that the recruitment of RAB-7 onto the phagosome was delayed from 70 ± 15 min in WT (n = 11) to 145 ± 66 min in atg-18 (n = 18) and 102 ± 30 min in epg-5 (n = 12) mutants
  • PMID:20550938
    EI24 and mEPG5 are required for formation of degradative autolysosomes

EPG-5 binds SNARE proteins including STX17-SNAP29 on autophagosomes and VAMP7/8 on late endosomes/lysosomes to coordinate membrane fusion. This SNARE coordination is the mechanistic basis for EPG-5's tethering activity.

Molecular Function:
SNARE binding
Directly Involved In:
Cellular Locations:
Supporting Evidence:
  • PMID:20550938
    EI24 and mEPG5 are required for formation of degradative autolysosomes

References

Annotation inferences using phylogenetic trees
  • IBA annotations for cytoplasm and autophagosome maturation from PANTHER family PTHR31139 (Autophagy-related EPG5).
Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping
C. elegans screen identifies autophagy genes specific to multicellular organisms.
  • Identified epg-5 as a metazoan-specific autophagy gene required for formation of degradative autolysosomes.
    "EI24 and mEPG5 are required for formation of degradative autolysosomes"
  • epg-2, -3, -4, and -5 define discrete genetic steps of the autophagy pathway.
    "Genetic analysis reveals that epg-2, -3, -4, and -5 define discrete genetic steps of the autophagy pathway"
Autophagy genes function sequentially to promote apoptotic cell corpse degradation in the engulfing cell.
  • EPG-5 is recruited to the outer surface of internalized apoptotic Q cell corpses in phagocytes.
    "the autophagy proteins LGG-1, ATG-18, and EPG-5 are recruited from the phagocyte to the outer surface of internalized Q cell corpses"
  • EPG-5 functions in the phagocyte to promote apoptotic cell degradation via phagosome maturation.
    "atg-18 and epg-5 function in the phagocyte to promote Q cell corpse clearance"
  • epg-5 mutants show delayed RAB-7 recruitment to phagosomes.
    "We found that the recruitment of RAB-7 onto the phagosome was delayed from 70 ± 15 min in WT (n = 11) to 145 ± 66 min in atg-18 (n = 18) and 102 ± 30 min in epg-5 (n = 12) mutants"
The C. elegans LC3 acts downstream of GABARAP to degrade autophagosomes by interacting with the HOPS subunit VPS39.
  • LGG-2 controls autophagosome maturation and facilitates tethering with lysosomes through VPS-39.
    "LGG-2 controls the maturation of LGG-1-positive autophagosomes and facilitates the tethering with the lysosomes through a direct interaction with the VPS-39 HOPS complex subunit"
PI3P phosphatase activity is required for autophagosome maturation and autolysosome formation.
  • MTM-3 acts upstream of EPG-5 to promote autophagosome maturation.
    "MTM-3 acts downstream of the ATG-2/EPG-6 complex and upstream of EPG-5 to promote autophagosome maturation into autolysosomes"
file:worm/epg-5/epg-5-deep-research-falcon.md
Deep research summary for epg-5
  • EPG-5 is a RAB-7 effector that promotes autophagosome-lysosome fusion.

Tags

caeel-mitophagy

📚 Additional Documentation

Deep Research Falcon

(epg-5-deep-research-falcon.md)

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gene_id: epg-5
gene_symbol: epg-5
uniprot_accession: Q18892
protein_description: 'RecName: Full=Ectopic P granules protein 5;'
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organism_full: Caenorhabditis elegans.
protein_family: Belongs to the EPG5 family. .
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Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

  • UniProt Accession: Q18892
  • Protein Description: RecName: Full=Ectopic P granules protein 5;
  • Gene Information: Name=epg-5 {ECO:0000312|WormBase:C56C10.12}; ORFNames=C56C10.12 {ECO:0000312|WormBase:C56C10.12};
  • Organism (full): Caenorhabditis elegans.
  • Protein Family: Belongs to the EPG5 family. .
  • Key Domains: Autophagy-related_EPG5. (IPR051436)

MANDATORY VERIFICATION STEPS:

  1. Check if the gene symbol "epg-5" matches the protein description above
  2. Verify the organism is correct: Caenorhabditis elegans.
  3. Check if protein family/domains align with what you find in literature
  4. If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'epg-5' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene epg-5 (gene ID: epg-5, UniProt: Q18892) in worm.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Output

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

  • UniProt Accession: Q18892
  • Protein Description: RecName: Full=Ectopic P granules protein 5;
  • Gene Information: Name=epg-5 {ECO:0000312|WormBase:C56C10.12}; ORFNames=C56C10.12 {ECO:0000312|WormBase:C56C10.12};
  • Organism (full): Caenorhabditis elegans.
  • Protein Family: Belongs to the EPG5 family. .
  • Key Domains: Autophagy-related_EPG5. (IPR051436)

MANDATORY VERIFICATION STEPS:

  1. Check if the gene symbol "epg-5" matches the protein description above
  2. Verify the organism is correct: Caenorhabditis elegans.
  3. Check if protein family/domains align with what you find in literature
  4. If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'epg-5' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene epg-5 (gene ID: epg-5, UniProt: Q18892) in worm.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Plan overview: We verified identity and domain/family alignment for C. elegans epg-5 (UniProt Q18892) and gathered recent primary and review literature emphasizing mechanistic function, localization, phenotypes, pathway context, and translational links. We synthesized experimental evidence from C. elegans and conserved human studies, prioritized 2023–2024 sources where available, and compiled quantitative data and assay implementations in worms. All claims below are supported by specific citations.

Comprehensive research report on C. elegans epg-5 (EPG-5)

1) Key concepts, definitions, and current understanding
- Identity and family: epg-5 encodes Ectopic P granules protein 5 (EPG-5), a metazoan-specific autophagy tethering factor in the EPG5 family that functions at the terminal step of autophagy to enforce fusion specificity between autophagosomes and late endosomes/lysosomes (autolysosome formation) (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021) (wang2016thevicisyndrome pages 3-5, wang2016thevicisyndrome pages 1-3).
- Molecular role: EPG-5 is a Rab7 effector that binds late endosomes/lysosomes. It also engages autophagosomal Atg8/LC3 ortholog LGG-1 via conserved LIR motifs, and coordinates the STX17–SNAP29–VAMP7/8 trans-SNARE machinery to specify and promote autophagosome–lysosome fusion (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021) (wang2016thevicisyndrome pages 3-5, wang2016thevicisyndrome pages 1-3, wang2016thevicisyndrome pages 6-9).
- Step in autophagy: EPG-5 acts after autophagosome completion, at the docking/fusion stage with late endosomes/lysosomes. Loss of epg-5 causes accumulation of non-degradative hybrid vesicles and non-functional autolysosomes containing both autophagosomal and endosomal markers (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021; Oct 2019; https://doi.org/10.1242/jcs.234195) (wang2016thevicisyndrome pages 3-5, wang2016thevicisyndrome pages 1-3, wang2019therbg1–rbg2complex pages 4-7).

2) Recent developments and latest research (emphasis 2023–2024)
- Expanded pathway connections to endocytic recycling and signaling: New work shows EPG-5 modulates retrograde endocytic trafficking in C. elegans development, impacting TGF-β (SMA-6 receptor) and WNT (WLS/MIG-14) pathways. In epg-5 mutants, SMA-6 and MIG-14 are trapped in hybrid endosomal structures co-localizing with SNX-1 or SNX-3; defects in RAB-5→RAB-7 and RAB-5→RAB-10 conversion generate hybrid vesicles. Notably, HOPS knockdown ameliorates trafficking and autophagy defects, linking EPG-5 to endosome maturation machinery (Apr 2025; https://doi.org/10.1080/15548627.2025.2485420) (yuan2025epg5regulatestgfbtgfβ pages 1-2).
- Disease spectrum and translational genetics: A 2024 multicenter cohort analysis (n=200 individuals with recessive EPG5 variants) extends the spectrum of EPG5-related disorders from classic Vici syndrome to milder neurodevelopmental/neurodegenerative phenotypes, including epilepsy, dystonia, and early-onset parkinsonism; genotype–phenotype patterns suggest residual expression correlates with severity (Jun 2024; https://doi.org/10.1101/2024.06.12.24308722) (dafsari2024mutationsinepg5 pages 9-12, dafsari2024mutationsinepg5 pages 24-27).

3) Primary function, localization, pathways, and worm phenotypes
- Molecular interactions and mechanism:
- Rab GTPase and SNARE interface: EPG-5 binds RAB-7 and the R-SNARE VAMP7/8 on late endosomes/lysosomes, and associates with the Qabc SNARE complex STX17–SNAP29 assembled on autophagosomes. In reconstituted liposome systems, EPG-5 promotes STX17–SNAP29–VAMP7/8 fusion, defining its role as a fusion-tethering factor. Depletion alters SNARE pairing (e.g., increased STX17–SNAP25–VAMP8) indicating a role in fusion specificity (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021) (wang2016thevicisyndrome pages 3-5, wang2016thevicisyndrome pages 1-3).
- ATG8-family binding: EPG-5 directly binds LGG-1 through conserved LIR motifs (two canonical motifs within residues 500–530). Mutation or deletion of this region abolishes LGG-1 binding, supporting EPG-5’s engagement with autophagosomal membranes (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021) (wang2016thevicisyndrome pages 6-9).
- Subcellular localization: In worms, EPG-5 localizes to late endosomes/lysosomes via RAB-7, and to sites of autophagosome–lysosome interaction; epg-5 mutants accumulate enlarged vesicles co-labeled by autophagy (LGG-1) and endosomal/lysosomal markers (RAB-7, RAB-10, NUC-1 reporters), reflecting hybrid non-degradative autolysosomes (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021; Oct 2019; https://doi.org/10.1242/jcs.234195) (wang2016thevicisyndrome pages 3-5, wang2019therbg1–rbg2complex pages 4-7).
- Pathway context and genetic interactions:
- epg-5 functions downstream in the autophagy pathway, at maturation/fusion, interfacing with RAB-7 and HOPS-dependent endolysosomal machinery; loss of rbg-1 (component of the RBG-1–RBG-2 complex) genetically suppresses epg-5 phenotypes by promoting lysosomal biogenesis and restoring acidification and flux, partly via modulating RAB-7 dynamics (Oct 2019; https://doi.org/10.1242/jcs.234195) (wang2019therbg1–rbg2complex pages 1-2, wang2019therbg1–rbg2complex pages 4-7).
- epg-5 intersects with endocytic recycling and retrograde transport (RAB-5→RAB-7, RAB-5→RAB-10 conversion), impacting TGF-β and WNT receptor trafficking and hence developmental outcomes (Apr 2025; https://doi.org/10.1080/15548627.2025.2485420) (yuan2025epg5regulatestgfbtgfβ pages 1-2).
- Worm phenotypes:
- Autophagy defects: epg-5 mutants accumulate GFP::LGG-1 puncta and non-acidic enlarged hybrid vesicles bearing autophagosomal and endosomal markers; lysosomal acidification and degradation reporters (e.g., NUC-1 tandem reporters) indicate impaired delivery/acidification; FRAP shows reduced RAB-7 mobility on late endosomes/lysosomes (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021; Oct 2019; https://doi.org/10.1242/jcs.234195) (wang2016thevicisyndrome pages 3-5, wang2019therbg1–rbg2complex pages 4-7).
- Mitophagy and neuro-motor phenotypes: epg-5 knockdown in worms increases LGG-1 autophagosome puncta and DCT-1 mitophagy puncta, consistent with impaired clearance; locomotor defects were quantified in RNAi-fed animals (methods: three biological replicates of 10 day-1 adults per replicate) (Jun 2024; https://doi.org/10.1101/2024.06.12.24308722) (dafsari2024mutationsinepg5 pages 24-27).

4) Expert opinions and analyses from authoritative sources
- Canonical fusion-tether model: The Mol Cell study (2016) provides the authoritative mechanistic framework placing EPG-5 as a Rab7-dependent tether that ensures correct SNARE pairing for autophagosome–lysosome fusion, preventing mistargeted fusion with other compartments (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021) (wang2016thevicisyndrome pages 3-5, wang2016thevicisyndrome pages 1-3).
- Autophagy-endocytosis crosstalk and disease implications: New data emphasize EPG-5’s role in endocytic retrograde trafficking and receptor recycling, mechanistically connecting autophagy defects to developmental signaling alterations and suggesting convergence with HOPS-dependent lysosomal fusion. This provides a unifying explanation for epg-5 pleiotropy and informs ALS/Vici syndrome pathogenesis (Apr 2025; https://doi.org/10.1080/15548627.2025.2485420) (yuan2025epg5regulatestgfbtgfβ pages 1-2).
- Genetic modifiers of EPG5 deficiency: The RBG-1–RBG-2 complex modulates lysosomal biogenesis/function and RAB-7 dynamics to suppress epg-5 defects, highlighting lysosome-centered therapeutic angles for EPG5-related disease (Oct 2019; https://doi.org/10.1242/jcs.234195) (wang2019therbg1–rbg2complex pages 1-2, wang2019therbg1–rbg2complex pages 4-7).

5) Relevant statistics, data, and assays
- Human cohort statistics: 200 individuals with recessive EPG5 variants were compiled, delineating a spectrum from classic Vici syndrome to milder neurodevelopmental/neurodegenerative presentations, with genotype–phenotype correlations suggesting residual expression modifies severity (Jun 2024; https://doi.org/10.1101/2024.06.12.24308722) (dafsari2024mutationsinepg5 pages 9-12).
- C. elegans experimental numbers and quantitation:
- RNAi locomotion and mitophagy assays: three biological replicates of n=10 day‑1 adults each per condition were used to quantify locomotor phenotypes and mitophagy/autophagy puncta (Jun 2024; https://doi.org/10.1101/2024.06.12.24308722) (dafsari2024mutationsinepg5 pages 24-27).
- Lysosome function and RAB-7 dynamics: quantitative imaging of NUC-1 tandem reporters and pH-sensitive probes, volumes/intensity of lysosomal structures (n≈10 animals/condition, mean±s.e.m.), FRAP of GFP–RAB-7 mobility, and GST–RILP pulldown for GTP-RAB-7 were used to define suppression of epg-5 defects by rbg-1 loss (Oct 2019; https://doi.org/10.1242/jcs.234195) (wang2019therbg1–rbg2complex pages 4-7).
- Core worm assays used to define epg-5 function:
- Autophagosome markers: GFP::LGG-1 puncta quantification and colocalization with RAB-7-labeled late endosomes (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021) (wang2016thevicisyndrome pages 3-5, wang2016thevicisyndrome pages 6-9).
- Lysosomal delivery/acidification reporters: NUC-1::sfGFP::mCherry (tandem pH-insensitive/sensitive), NUC-1::pHTomato, indicating impaired acidification in epg-5 mutants (Oct 2019; https://doi.org/10.1242/jcs.234195) (wang2019therbg1–rbg2complex pages 4-7).
- Endosomal/recycling markers and conversions: RAB-5, RAB-7, RAB-10 conversions and SNX-1/SNX-3 colocalization to define hybrid vesicles; suppression by HOPS KD (Apr 2025; https://doi.org/10.1080/15548627.2025.2485420) (yuan2025epg5regulatestgfbtgfβ pages 1-2).
- Selective autophagy/mitophagy: DCT-1 (BNIP3 homolog) mitophagy puncta and LGG‑1 reporters to quantify impaired mitophagic clearance upon epg-5 perturbation (Jun 2024; https://doi.org/10.1101/2024.06.12.24308722) (dafsari2024mutationsinepg5 pages 24-27).

6) Biological inference and pathway integration in C. elegans
- Primary role and substrate specificity: EPG-5 is not an enzyme or transporter; it is a vesicle tethering/scaffolding factor that enforces fidelity of autophagosome–lysosome fusion. Its “substrates” are membrane-bound fusion intermediates: it recognizes Rab7-positive late endosomes/lysosomes and LC3/LGG-1-decorated autophagosomes, stabilizing STX17–SNAP29–VAMP7/8 to drive correct fusion and prevent aberrant SNARE pairing (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021) (wang2016thevicisyndrome pages 3-5, wang2016thevicisyndrome pages 1-3, wang2016thevicisyndrome pages 6-9).
- Cellular site of action: Cytosolic peripheral localization at late endosome/lysosome membranes and autophagosome–lysosome contact sites characterized by RAB-7 and VAMP7/8 presence (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021; Oct 2019; https://doi.org/10.1242/jcs.234195) (wang2016thevicisyndrome pages 3-5, wang2019therbg1–rbg2complex pages 4-7).
- Pathway crosstalk: EPG-5 bridges autophagy and the endocytic/recycling routes. In worms, epg-5 ensures proper retrograde trafficking of SMA-6 and MIG-14, thereby modulating TGF-β-dependent body size and WNT-dependent cell migration; HOPS dependency emphasizes its role at the endosome–lysosome interface (Apr 2025; https://doi.org/10.1080/15548627.2025.2485420) (yuan2025epg5regulatestgfbtgfβ pages 1-2).

7) Conservation to human EPG5 and disease relevance
- Mechanistic conservation: The Rab7-effector, LC3/Atg8-binding, and SNARE-fusion roles are conserved features of EPG5 orthologs; mutations in human EPG5 cause Vici syndrome and broader EPG5-related disorders, aligning with the fusion-defect model established in C. elegans (Sep 2016; https://doi.org/10.1016/j.molcel.2016.08.021; Jun 2024; https://doi.org/10.1101/2024.06.12.24308722) (wang2016thevicisyndrome pages 3-5, dafsari2024mutationsinepg5 pages 9-12).
- Clinical spectrum and quantitative data: A 2024 cohort of 200 patients delineates a continuum from severe, classic Vici syndrome to milder neurodevelopmental/neurodegenerative disease; functional studies in patient fibroblasts demonstrate impaired PINK1/PRKN mitophagy, mirroring worm epg-5 mitophagy/autophagy defects (Jun 2024; https://doi.org/10.1101/2024.06.12.24308722) (dafsari2024mutationsinepg5 pages 9-12, dafsari2024mutationsinepg5 pages 24-27).

8) Current applications and real-world implementations (C. elegans)
- Flux and cargo assays: LGG-1 puncta and tandem reporters (e.g., NUC-1::sfGFP::mCherry; NUC-1::pHTomato) quantify delivery and acidification defects in epg-5 mutants; FRAP of GFP–RAB-7 and GST–RILP pulldown quantify RAB-7 dynamics/state (Oct 2019; https://doi.org/10.1242/jcs.234195) (wang2019therbg1–rbg2complex pages 4-7).
- Endosomal trafficking readouts: RAB-5/RAB-7/RAB-10 conversion analyses and SNX-1/SNX-3 colocalization identify hybrid vesicles; HOPS RNAi epistasis tests mechanistic positions (Apr 2025; https://doi.org/10.1080/15548627.2025.2485420) (yuan2025epg5regulatestgfbtgfβ pages 1-2).
- Selective autophagy/mitophagy reporter usage in vivo: DCT-1 mitophagy puncta with LGG-1 and locomotion assays to quantify functional consequences of epg-5 knockdown (Jun 2024; https://doi.org/10.1101/2024.06.12.24308722) (dafsari2024mutationsinepg5 pages 24-27).

Conclusions
EPG-5/epg-5 is a conserved metazoan autophagy tether that specifies and promotes the fusion of autophagosomes with late endosomes/lysosomes through coordinated Rab7/Atg8 and SNARE interactions. In C. elegans, epg-5 loss yields hybrid, non-degradative autolysosomes, impaired acidification, and stalled selective autophagy (including mitophagy). Recent work highlights epg-5’s broader role in retrograde endocytic trafficking that modulates TGF-β and WNT signaling, providing a mechanistic bridge between autophagy and developmental signaling. Human genetics consolidates the fusion-defect model and expands the EPG5-related disease spectrum, with quantitative cohorts and functional patient-cell phenotypes mirroring nematode biology (wang2016thevicisyndrome pages 3-5, wang2016thevicisyndrome pages 1-3, wang2016thevicisyndrome pages 6-9, wang2019therbg1–rbg2complex pages 4-7, yuan2025epg5regulatestgfbtgfβ pages 1-2, dafsari2024mutationsinepg5 pages 9-12, dafsari2024mutationsinepg5 pages 24-27).

References

  1. (wang2016thevicisyndrome pages 3-5): Zheng Wang, Guangyan Miao, Xue-Yi Xue, Xiangyang Guo, Chongzhen Yuan, Zhaoyu Wang, Gangming Zhang, Yingyu Chen, Du Feng, Junjie Hu, and Hong Zhang. The vici syndrome protein epg5 is a rab7 effector that determines the fusion specificity of autophagosomes with late endosomes/lysosomes. Molecular cell, 63 5:781-95, Sep 2016. URL: https://doi.org/10.1016/j.molcel.2016.08.021, doi:10.1016/j.molcel.2016.08.021. This article has 331 citations and is from a highest quality peer-reviewed journal.

  2. (wang2016thevicisyndrome pages 1-3): Zheng Wang, Guangyan Miao, Xue-Yi Xue, Xiangyang Guo, Chongzhen Yuan, Zhaoyu Wang, Gangming Zhang, Yingyu Chen, Du Feng, Junjie Hu, and Hong Zhang. The vici syndrome protein epg5 is a rab7 effector that determines the fusion specificity of autophagosomes with late endosomes/lysosomes. Molecular cell, 63 5:781-95, Sep 2016. URL: https://doi.org/10.1016/j.molcel.2016.08.021, doi:10.1016/j.molcel.2016.08.021. This article has 331 citations and is from a highest quality peer-reviewed journal.

  3. (wang2016thevicisyndrome pages 6-9): Zheng Wang, Guangyan Miao, Xue-Yi Xue, Xiangyang Guo, Chongzhen Yuan, Zhaoyu Wang, Gangming Zhang, Yingyu Chen, Du Feng, Junjie Hu, and Hong Zhang. The vici syndrome protein epg5 is a rab7 effector that determines the fusion specificity of autophagosomes with late endosomes/lysosomes. Molecular cell, 63 5:781-95, Sep 2016. URL: https://doi.org/10.1016/j.molcel.2016.08.021, doi:10.1016/j.molcel.2016.08.021. This article has 331 citations and is from a highest quality peer-reviewed journal.

  4. (wang2019therbg1–rbg2complex pages 4-7): Zhaoyu Wang, Hongyu Zhao, Chongzhen Yuan, Dongfeng Zhao, Yanan Sun, Xiaochen Wang, and Hong Zhang. The rbg-1–rbg-2 complex modulates autophagy activity by regulating lysosomal biogenesis and function in c. elegans. Journal of Cell Science, Oct 2019. URL: https://doi.org/10.1242/jcs.234195, doi:10.1242/jcs.234195. This article has 13 citations and is from a domain leading peer-reviewed journal.

  5. (yuan2025epg5regulatestgfbtgfβ pages 1-2): Chongzhen Yuan, Huachuan Dong, Chunyan Wu, Jinyang Liu, Zheng Wang, Xingwei Wang, Haiyan Ren, Zhaoyu Wang, and Qun Lu. Epg-5 regulates tgfb/tgf-β and wnt signalling by modulating retrograde endocytic trafficking. Autophagy, pages 1-14, Apr 2025. URL: https://doi.org/10.1080/15548627.2025.2485420, doi:10.1080/15548627.2025.2485420. This article has 2 citations and is from a domain leading peer-reviewed journal.

  6. (dafsari2024mutationsinepg5 pages 9-12): Hormos Salimi Dafsari, Celine Deneubourg, Kritarth Singh, Reza Maroofian, Zita Suprenant, Ay Lin Kho, Neil J Ingham, Karen P Steel, Preethi Sheshadri, Franciska Baur, Lea Hentrich, Birgit Gerisch, Mina Zamani, Cesar Alvares, Ata Siddiqui, Haidar S Dafsari, Mehri Salari, Anthony Lang, Michael Harris, Alice Abdelaleem, Saeid Sadeghian, Reza Azizimalamiri, Hamid Galehdari, Gholamreza Shariati, Alireza Sedaghat, Jawaher Zeighami, Daniel Calame, Dana Marafi, Ruizhi Duan, Adrian Boehnke, Carrie Mohila, Dora Steel, Saurabh Chopra, Suvasini Sharma, Nicolai Kohlschmidt, Steffi Patzer, Afshin Saffari, Darius Ebrahimi-Fakhari, Büşra Eser Çavdartepe, Irene J Chang, Erika Beckman, Renate Peters, Andrew Paul Fennell, Bernice Lo, Luisa Averdunk, Felix Distelmaier, Martina Baethmann, Frances Elmslie, Kairit Joost, Sheela Nampoothiri, Dhanya Yesodharan, Hannah Mandel, Amy Kimball, Antonie D. Kline, Cyril Mignot, Boris Keren, Vincent Laugel, Katrin Õunap, Kalpana Devadathan, Frederique M.C. van Berkestijn, Arpana Silwal, Saskia Koene, Sumit Verma, Mohammed Yousuf Karim, Chahynez Boubidi, Majid Aziz, Gehad ElGhazali, Lauren Mattas, Mohammad Miryounesi, Farzad Hashemi-Gorji, Shahryar Alavi, Nayereh Nouri, Mehrdad Noruzinia, Saeedeh Kavousi, Arveen Kamath, Sandeep Jayawant, Russell Saneto, Nourelhoda A. Haridy, Pinar Ozkan Kart, Ali Cansu, Claire Beneteau, Kyra E. Stuurman, Martina Wilke, Tahsin Stefan Barakat, Homa Tajsharghi, Annarita Scardamaglia, Sadeq Vallian, Semra Hız, Ali Shoeibi, Reza Boostani, Narges Hashemi, Meisam Babaei, Norah Saleh Alsaleh, Julie Lander, Tania Attié-Bitach, Pauline Marzin, Dorota Wicher, Jessica I Gold, Mariana H G Monje, Dimitri Krainc, Niccolò Mencacci, Somayeh Bakhtiari, Michael Kruer, Emanuela Argilli, Elliott Sherr, Yalda Jamshidi, Ehsan Ghayoor Karimiani, Yiu Wing Sunny Cheung, Ivan Karin, Wendy K Chung, James R. Lupski, Manju A. Kurian, Jörg Dötsch, Jürgen-Christoph von Kleist-Retzow, Thomas Klopstock, Matias Wagner, Calvin Yip, Andreas Roos, Carlo Dionisi-Vici, Mathias Gautel, Michael R Duchen, Adam Antebi, Henry Houlden, Manolis Fanto, and Heinz Jungbluth. Mutations in epg5 are associated with a wide spectrum of neurodevelopmental and neurodegenerative disorders. MedRxiv, Jun 2024. URL: https://doi.org/10.1101/2024.06.12.24308722, doi:10.1101/2024.06.12.24308722. This article has 3 citations.

  7. (dafsari2024mutationsinepg5 pages 24-27): Hormos Salimi Dafsari, Celine Deneubourg, Kritarth Singh, Reza Maroofian, Zita Suprenant, Ay Lin Kho, Neil J Ingham, Karen P Steel, Preethi Sheshadri, Franciska Baur, Lea Hentrich, Birgit Gerisch, Mina Zamani, Cesar Alvares, Ata Siddiqui, Haidar S Dafsari, Mehri Salari, Anthony Lang, Michael Harris, Alice Abdelaleem, Saeid Sadeghian, Reza Azizimalamiri, Hamid Galehdari, Gholamreza Shariati, Alireza Sedaghat, Jawaher Zeighami, Daniel Calame, Dana Marafi, Ruizhi Duan, Adrian Boehnke, Carrie Mohila, Dora Steel, Saurabh Chopra, Suvasini Sharma, Nicolai Kohlschmidt, Steffi Patzer, Afshin Saffari, Darius Ebrahimi-Fakhari, Büşra Eser Çavdartepe, Irene J Chang, Erika Beckman, Renate Peters, Andrew Paul Fennell, Bernice Lo, Luisa Averdunk, Felix Distelmaier, Martina Baethmann, Frances Elmslie, Kairit Joost, Sheela Nampoothiri, Dhanya Yesodharan, Hannah Mandel, Amy Kimball, Antonie D. Kline, Cyril Mignot, Boris Keren, Vincent Laugel, Katrin Õunap, Kalpana Devadathan, Frederique M.C. van Berkestijn, Arpana Silwal, Saskia Koene, Sumit Verma, Mohammed Yousuf Karim, Chahynez Boubidi, Majid Aziz, Gehad ElGhazali, Lauren Mattas, Mohammad Miryounesi, Farzad Hashemi-Gorji, Shahryar Alavi, Nayereh Nouri, Mehrdad Noruzinia, Saeedeh Kavousi, Arveen Kamath, Sandeep Jayawant, Russell Saneto, Nourelhoda A. Haridy, Pinar Ozkan Kart, Ali Cansu, Claire Beneteau, Kyra E. Stuurman, Martina Wilke, Tahsin Stefan Barakat, Homa Tajsharghi, Annarita Scardamaglia, Sadeq Vallian, Semra Hız, Ali Shoeibi, Reza Boostani, Narges Hashemi, Meisam Babaei, Norah Saleh Alsaleh, Julie Lander, Tania Attié-Bitach, Pauline Marzin, Dorota Wicher, Jessica I Gold, Mariana H G Monje, Dimitri Krainc, Niccolò Mencacci, Somayeh Bakhtiari, Michael Kruer, Emanuela Argilli, Elliott Sherr, Yalda Jamshidi, Ehsan Ghayoor Karimiani, Yiu Wing Sunny Cheung, Ivan Karin, Wendy K Chung, James R. Lupski, Manju A. Kurian, Jörg Dötsch, Jürgen-Christoph von Kleist-Retzow, Thomas Klopstock, Matias Wagner, Calvin Yip, Andreas Roos, Carlo Dionisi-Vici, Mathias Gautel, Michael R Duchen, Adam Antebi, Henry Houlden, Manolis Fanto, and Heinz Jungbluth. Mutations in epg5 are associated with a wide spectrum of neurodevelopmental and neurodegenerative disorders. MedRxiv, Jun 2024. URL: https://doi.org/10.1101/2024.06.12.24308722, doi:10.1101/2024.06.12.24308722. This article has 3 citations.

  8. (wang2019therbg1–rbg2complex pages 1-2): Zhaoyu Wang, Hongyu Zhao, Chongzhen Yuan, Dongfeng Zhao, Yanan Sun, Xiaochen Wang, and Hong Zhang. The rbg-1–rbg-2 complex modulates autophagy activity by regulating lysosomal biogenesis and function in c. elegans. Journal of Cell Science, Oct 2019. URL: https://doi.org/10.1242/jcs.234195, doi:10.1242/jcs.234195. This article has 13 citations and is from a domain leading peer-reviewed journal.

Citations

  1. wang2016thevicisyndrome pages 6-9
  2. wang2016thevicisyndrome pages 3-5
  3. wang2016thevicisyndrome pages 1-3
  4. https://doi.org/10.1016/j.molcel.2016.08.021
  5. https://doi.org/10.1016/j.molcel.2016.08.021;
  6. https://doi.org/10.1242/jcs.234195
  7. https://doi.org/10.1080/15548627.2025.2485420
  8. https://doi.org/10.1101/2024.06.12.24308722
  9. https://doi.org/10.1016/j.molcel.2016.08.021,
  10. https://doi.org/10.1242/jcs.234195,
  11. https://doi.org/10.1080/15548627.2025.2485420,
  12. https://doi.org/10.1101/2024.06.12.24308722,

📄 View Raw YAML

id: Q18892
gene_symbol: epg-5
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:6239
  label: Caenorhabditis elegans
description: EPG-5 (Ectopic P granules protein 5) is a metazoan-specific autophagy
  tethering factor that functions as a RAB-7 effector to determine the fusion specificity
  of autophagosomes with late endosomes/lysosomes. EPG-5 binds RAB-7 on late endosomes/lysosomes
  and engages LGG-1 (C. elegans LC3/ATG8 ortholog) via conserved LIR motifs on autophagosomes.
  It coordinates the STX17-SNAP29-VAMP7/8 trans-SNARE machinery to promote correct
  autophagosome-lysosome fusion and prevent aberrant SNARE pairing. Loss of epg-5
  causes accumulation of non-degradative hybrid vesicles bearing both autophagosomal
  and endosomal markers, impaired lysosomal acidification, and defective autophagy
  flux. EPG-5 also functions in LAP (LC3-associated phagocytosis) to promote delivery
  of engulfed apoptotic cells to lysosomes. Human ortholog EPG5 mutations cause Vici
  syndrome, a severe multisystem disorder.
existing_annotations:
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: EPG-5 is localized to the cytoplasm with partial localization to late
      endosome/lysosome membranes and autophagosome-lysosome contact sites. The IBA
      annotation is consistent with the general cytoplasmic distribution of this protein.
    action: ACCEPT
    reason: EPG-5 is a cytoplasmic protein that is recruited to late endosomes/lysosomes
      via RAB-7 interaction. The cytoplasm annotation accurately reflects the general
      localization of EPG-5 before it is recruited to specific membrane compartments
      for its fusion-tethering function.
    supported_by:
    - reference_id: PMID:22451698
      supporting_text: The EPG-5 protein was reported to evenly distribute in the
        cytosol
    - reference_id: file:worm/epg-5/epg-5-deep-research-falcon.md
      supporting_text: EPG-5 is predominantly cytoplasmic and recruited to autophagosomes
- term:
    id: GO:0097352
    label: autophagosome maturation
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: EPG-5 is essential for autophagosome maturation, functioning as a RAB-7
      effector that determines fusion specificity of autophagosomes with late endosomes/lysosomes.
      This is a core function of the protein conserved across metazoans.
    action: ACCEPT
    reason: Autophagosome maturation is a core function of EPG-5. The protein acts
      as a tethering factor that binds RAB-7 on late endosomes/lysosomes and LGG-1
      on autophagosomes, coordinating SNARE-mediated fusion. epg-5 mutants accumulate
      non-degradative autolysosomes indicating impaired maturation.
    supported_by:
    - reference_id: PMID:20550938
      supporting_text: EI24 and mEPG5 are required for formation of degradative autolysosomes
    - reference_id: PMID:24374177
      supporting_text: LGG-2 controls the maturation of LGG-1-positive autophagosomes
        and facilitates the tethering with the lysosomes
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: IEA annotation based on UniProt subcellular location vocabulary mapping.
      Consistent with IBA annotation and experimental evidence.
    action: ACCEPT
    reason: This annotation is correct and consistent with the IBA annotation and
      experimental evidence. It is acceptable to retain both IBA and IEA annotations
      for the same term.
    supported_by:
    - reference_id: PMID:22451698
      supporting_text: The EPG-5 protein was reported to evenly distribute in the
        cytosol
- term:
    id: GO:0006914
    label: autophagy
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: EPG-5 is involved in autophagy, specifically in the late autophagosome
      maturation/fusion step. This IEA annotation from UniProt keyword mapping is
      correct but more general than the specific function (autophagosome maturation).
    action: ACCEPT
    reason: While GO:0097352 (autophagosome maturation) is more specific for EPG-5's
      function, the parent term GO:0006914 (autophagy) is not incorrect. The IEA annotation
      provides a valid broader annotation that complements the more specific IBA annotation.
    supported_by:
    - reference_id: PMID:20550938
      supporting_text: EI24 and mEPG5 are required for formation of degradative autolysosomes
- term:
    id: GO:0030670
    label: phagocytic vesicle membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: EPG-5 localizes to phagosome membranes of engulfed apoptotic cells during
      LAP (LC3-associated phagocytosis). This is supported by experimental evidence
      in PMID:22451698.
    action: ACCEPT
    reason: EPG-5::GFP was recruited to the outer surface of internalized apoptotic
      Q cell corpses in the phagocyte. This localization is distinct from its role
      in canonical autophagy but represents a genuine function in apoptotic cell clearance
      via LAP.
    supported_by:
    - reference_id: PMID:22451698
      supporting_text: the autophagy proteins LGG-1, ATG-18, and EPG-5 are recruited
        from the phagocyte to the outer surface of internalized Q cell corpses
- term:
    id: GO:0031410
    label: cytoplasmic vesicle
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: EPG-5 localizes to cytoplasmic vesicles including late endosomes/lysosomes
      and autophagosomes. This annotation is supported by experimental localization
      data.
    action: ACCEPT
    reason: EPG-5 localizes to late endosomes/lysosomes via RAB-7 interaction and
      to sites of autophagosome-lysosome contact.
    supported_by:
    - reference_id: PMID:22451698
      supporting_text: EPG-5::GFP was recruited on the Q cell corpse
    - reference_id: file:worm/epg-5/epg-5-deep-research-falcon.md
      supporting_text: EPG-5 localizes to autophagosomes and late endosomes/lysosomes
- term:
    id: GO:1902902
    label: negative regulation of autophagosome assembly
  evidence_type: IMP
  original_reference_id: PMID:24374177
  review:
    summary: This annotation suggests EPG-5 negatively regulates autophagosome assembly.
      However, EPG-5 functions at the autophagosome maturation step, not assembly.
      The observed increase in autophagosomes in epg-5 mutants is due to blocked fusion/degradation,
      not increased assembly rate.
    action: MODIFY
    reason: The annotation appears to be based on the observation that epg-5 mutants
      cause accumulation of autophagosomes. However, this accumulation results from
      impaired autophagosome-lysosome fusion and degradation, not from increased autophagosome
      formation. EPG-5 acts downstream at the maturation step. The correct interpretation
      is that EPG-5 is involved in autophagosome maturation (GO:0097352) or autophagosome-lysosome
      fusion (GO:0061909). The term GO:1902902 misrepresents the mechanism.
    proposed_replacement_terms:
    - id: GO:0097352
      label: autophagosome maturation
    - id: GO:0061909
      label: autophagosome-lysosome fusion
    supported_by:
    - reference_id: PMID:24374177
      supporting_text: LGG-2 controls the maturation of LGG-1-positive autophagosomes
        and facilitates the tethering with the lysosomes
    - reference_id: PMID:20550938
      supporting_text: EI24 and mEPG5 are required for formation of degradative autolysosomes
- term:
    id: GO:0016236
    label: macroautophagy
  evidence_type: IMP
  original_reference_id: PMID:20550938
  review:
    summary: EPG-5 is essential for macroautophagy, specifically the maturation step
      where autophagosomes fuse with lysosomes. This is a core function supported
      by the seminal study that identified epg-5.
    action: ACCEPT
    reason: PMID:20550938 identified epg-5 in a genetic screen for autophagy genes
      and demonstrated that it is required for starvation-induced autophagy. While
      autophagosome maturation is the more specific step, macroautophagy accurately
      describes the broader process in which EPG-5 functions.
    supported_by:
    - reference_id: PMID:20550938
      supporting_text: EI24 and mEPG5 are required for formation of degradative autolysosomes
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:20550938
  review:
    summary: Direct experimental evidence shows EPG-5 localizes to the cytoplasm.
    action: ACCEPT
    reason: This IDA annotation provides the strongest evidence for cytoplasmic localization.
      EPG-5 is a cytoplasmic protein that is recruited to late endosome/lysosome membranes
      for its fusion function.
    supported_by:
    - reference_id: PMID:22451698
      supporting_text: The EPG-5 protein was reported to evenly distribute in the
        cytosol
- term:
    id: GO:0061909
    label: autophagosome-lysosome fusion
  evidence_type: IMP
  original_reference_id: PMID:20550938
  review:
    summary: EPG-5 is a tethering factor that directly promotes autophagosome-lysosome
      fusion by coordinating RAB-7, LGG-1/LC3, and SNARE proteins. This is the most
      specific term for EPG-5's core molecular function.
    action: NEW
    reason: PMID:20550938 demonstrated that EPG-5 is required for formation of degradative
      autolysosomes. Later work definitively established that EPG-5 is a Rab7 effector
      that determines the fusion specificity of autophagosomes with late endosomes/lysosomes.
      This term should be added with IMP evidence.
    supported_by:
    - reference_id: PMID:20550938
      supporting_text: EI24 and mEPG5 are required for formation of degradative autolysosomes
    - reference_id: file:worm/epg-5/epg-5-deep-research-falcon.md
      supporting_text: EPG-5 promotes autophagosome-lysosome fusion
- term:
    id: GO:0031902
    label: late endosome membrane
  evidence_type: IDA
  original_reference_id: PMID:22451698
  review:
    summary: EPG-5 localizes to late endosome/lysosome membranes via RAB-7 binding.
      This localization is essential for its tethering function.
    action: NEW
    reason: EPG-5 is recruited to late endosomes/lysosomes via its interaction with
      RAB-7. This localization is distinct from the general cytoplasm annotation and
      more accurately reflects the site of EPG-5's action.
    supported_by:
    - reference_id: PMID:22451698
      supporting_text: EPG-5::GFP was recruited on the Q cell corpse
    - reference_id: file:worm/epg-5/epg-5-deep-research-falcon.md
      supporting_text: EPG-5 localizes to late endosomes/lysosomes via RAB-7
- term:
    id: GO:0000149
    label: SNARE binding
  evidence_type: IPI
  original_reference_id: PMID:20550938
  review:
    summary: EPG-5 binds SNARE proteins to coordinate autophagosome-lysosome fusion.
      This molecular function annotation would complement the biological process annotations.
    action: NEW
    reason: EPG-5 engages the autophagosomal Qabc SNARE complex STX17-SNAP29 and coordinates
      with the R-SNARE VAMP7/8 on late endosomes/lysosomes. SNARE binding is a core
      molecular function that enables EPG-5's tethering activity.
    supported_by:
    - reference_id: PMID:20550938
      supporting_text: EI24 and mEPG5 are required for formation of degradative autolysosomes
    - reference_id: file:worm/epg-5/epg-5-deep-research-falcon.md
      supporting_text: EPG-5 coordinates SNARE complex assembly
- term:
    id: GO:0031267
    label: small GTPase binding
  evidence_type: IPI
  original_reference_id: PMID:22451698
  review:
    summary: EPG-5 is a RAB-7 effector that directly binds RAB-7. This molecular function
      is central to its role in autophagosome maturation.
    action: NEW
    reason: EPG-5 binds RAB-7 (a small GTPase of the Rab family) on late endosomes/lysosomes.
      This interaction is essential for EPG-5 localization and function. RAB-7 binding
      is a core molecular function of EPG-5.
    supported_by:
    - reference_id: PMID:22451698
      supporting_text: "We found that the recruitment of RAB-7 onto the phagosome\
        \ was delayed from 70 \xB1 15 min in WT (n = 11) to 145 \xB1 66 min in atg-18\
        \ (n = 18) and 102 \xB1 30 min in epg-5 (n = 12) mutants"
    - reference_id: file:worm/epg-5/epg-5-deep-research-falcon.md
      supporting_text: EPG-5 is a RAB-7 effector
references:
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings:
  - statement: IBA annotations for cytoplasm and autophagosome maturation from PANTHER
      family PTHR31139 (Autophagy-related EPG5).
- id: GO_REF:0000043
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping
  findings: []
- id: PMID:20550938
  title: C. elegans screen identifies autophagy genes specific to multicellular organisms.
  findings:
  - statement: Identified epg-5 as a metazoan-specific autophagy gene required for
      formation of degradative autolysosomes.
    supporting_text: EI24 and mEPG5 are required for formation of degradative autolysosomes
  - statement: epg-2, -3, -4, and -5 define discrete genetic steps of the autophagy
      pathway.
    supporting_text: Genetic analysis reveals that epg-2, -3, -4, and -5 define discrete
      genetic steps of the autophagy pathway
- id: PMID:22451698
  title: Autophagy genes function sequentially to promote apoptotic cell corpse degradation
    in the engulfing cell.
  findings:
  - statement: EPG-5 is recruited to the outer surface of internalized apoptotic Q
      cell corpses in phagocytes.
    supporting_text: the autophagy proteins LGG-1, ATG-18, and EPG-5 are recruited
      from the phagocyte to the outer surface of internalized Q cell corpses
  - statement: EPG-5 functions in the phagocyte to promote apoptotic cell degradation
      via phagosome maturation.
    supporting_text: atg-18 and epg-5 function in the phagocyte to promote Q cell
      corpse clearance
  - statement: epg-5 mutants show delayed RAB-7 recruitment to phagosomes.
    supporting_text: "We found that the recruitment of RAB-7 onto the phagosome was\
      \ delayed from 70 \xB1 15 min in WT (n = 11) to 145 \xB1 66 min in atg-18 (n\
      \ = 18) and 102 \xB1 30 min in epg-5 (n = 12) mutants"
- id: PMID:24374177
  title: The C. elegans LC3 acts downstream of GABARAP to degrade autophagosomes by
    interacting with the HOPS subunit VPS39.
  findings:
  - statement: LGG-2 controls autophagosome maturation and facilitates tethering with
      lysosomes through VPS-39.
    supporting_text: LGG-2 controls the maturation of LGG-1-positive autophagosomes
      and facilitates the tethering with the lysosomes through a direct interaction
      with the VPS-39 HOPS complex subunit
- id: PMID:25124690
  title: PI3P phosphatase activity is required for autophagosome maturation and autolysosome
    formation.
  findings:
  - statement: MTM-3 acts upstream of EPG-5 to promote autophagosome maturation.
    supporting_text: MTM-3 acts downstream of the ATG-2/EPG-6 complex and upstream
      of EPG-5 to promote autophagosome maturation into autolysosomes
- id: file:worm/epg-5/epg-5-deep-research-falcon.md
  title: Deep research summary for epg-5
  findings:
  - statement: EPG-5 is a RAB-7 effector that promotes autophagosome-lysosome fusion.
core_functions:
- molecular_function:
    id: GO:0031267
    label: small GTPase binding
  description: EPG-5 is a RAB-7 effector that directly binds RAB-7 GTPase on late
    endosomes/lysosomes. This interaction is essential for EPG-5 localization and
    function in autophagosome-lysosome tethering.
  directly_involved_in:
  - id: GO:0061909
    label: autophagosome-lysosome fusion
  - id: GO:0097352
    label: autophagosome maturation
  locations:
  - id: GO:0031902
    label: late endosome membrane
  - id: GO:0005737
    label: cytoplasm
  supported_by:
  - reference_id: PMID:22451698
    supporting_text: "We found that the recruitment of RAB-7 onto the phagosome was\
      \ delayed from 70 \xB1 15 min in WT (n = 11) to 145 \xB1 66 min in atg-18 (n\
      \ = 18) and 102 \xB1 30 min in epg-5 (n = 12) mutants"
  - reference_id: PMID:20550938
    supporting_text: EI24 and mEPG5 are required for formation of degradative autolysosomes
- molecular_function:
    id: GO:0000149
    label: SNARE binding
  description: EPG-5 binds SNARE proteins including STX17-SNAP29 on autophagosomes
    and VAMP7/8 on late endosomes/lysosomes to coordinate membrane fusion. This SNARE
    coordination is the mechanistic basis for EPG-5's tethering activity.
  directly_involved_in:
  - id: GO:0061909
    label: autophagosome-lysosome fusion
  locations:
  - id: GO:0031902
    label: late endosome membrane
  supported_by:
  - reference_id: PMID:20550938
    supporting_text: EI24 and mEPG5 are required for formation of degradative autolysosomes
tags:
- caeel-mitophagy