id: O15342 gene_symbol: ATP6V0E1 product_type: PROTEIN status: COMPLETE taxon: id: NCBITaxon:9606 label: Homo sapiens description: >- ATP6V0E1 encodes V-type proton ATPase subunit e 1 (81 amino acids, 9.2 kDa), a small dual-transmembrane protein that is a structural component of the V0 membrane-embedded domain of the vacuolar-type H+-ATPase (V-ATPase). The V0 complex contains the proton transport subunit a, a proteolipid c-ring, rotary subunit d, subunits e and f, and accessory subunits ATP6AP1 and ATP6AP2. Subunit e 1 has an N-terminal lumenal segment, two transmembrane helices, a short cytoplasmic loop, and a C-terminal lumenal tail bearing an N-linked glycan at Asn70 that contributes to V-ATPase assembly and stability. Humans have two paralogous e subunits: ATP6V0E1 (e1, ubiquitous) and ATP6V0E2 (e2, restricted to kidney and brain). Both isoforms can complement a yeast e subunit deletion, confirming that the e subunit is essential for proton pump function. ATP6V0E1 localizes to lysosomal and endosomal membranes as part of the assembled V-ATPase holoenzyme. As a V0 structural subunit, it contributes to the proton translocation function of the V-ATPase complex that acidifies lysosomes, endosomes, and other intracellular compartments. existing_annotations: - term: id: GO:1902600 label: proton transmembrane transport evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in review: summary: IBA phylogenetic transfer; proton transmembrane transport is the core function of the V-ATPase, and subunit e1 is required for this activity. action: ACCEPT reason: Proton transmembrane transport is the fundamental process of the V-ATPase. Both e1 and e2 are essential for proton pump function as shown by yeast complementation (PMID:17350184). - term: id: GO:0000220 label: vacuolar proton-transporting V-type ATPase, V0 domain evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: part_of review: summary: IBA phylogenetic transfer; V0 domain membership is confirmed by cryo-EM structure (PMID:33065002). action: ACCEPT reason: ATP6V0E1 is a confirmed V0 domain component as shown by cryo-EM structures of the complete human V-ATPase (PMID:33065002). supported_by: - reference_id: file:human/ATP6V0E1/ATP6V0E1-uniprot.txt supporting_text: The proton translocation complex V0 consists of the proton transport subunit a, a ring of proteolipid subunits c9c'', rotary subunit d, subunits e and f, and the accessory subunits ATP6AP1/Ac45 and ATP6AP2/PRR - term: id: GO:0016020 label: membrane evidence_type: IEA original_reference_id: GO_REF:0000044 qualifier: located_in review: summary: IEA from UniProt keyword mapping; generic membrane term consistent with dual-transmembrane topology of e1 subunit. action: MODIFY reason: Generic membrane is less informative than the more specific lysosomal and endosomal membrane annotations already present. The dual-TM topology and V0 domain membership place it specifically at vesicular membranes. proposed_replacement_terms: - id: GO:0005765 label: lysosomal membrane - term: id: GO:0033179 label: proton-transporting V-type ATPase, V0 domain evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: part_of review: summary: IEA from InterPro; V0 domain membership is experimentally confirmed. action: ACCEPT reason: V0 domain membership is directly confirmed by cryo-EM structures (PMID:33065002). - term: id: GO:0046961 label: proton-transporting ATPase activity, rotational mechanism evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: enables review: summary: IEA from InterPro; rotational mechanism ATPase activity is the complex-level activity to which e1 contributes. action: ACCEPT reason: The V-ATPase employs a rotational mechanism. Subunit e1 as a V0 structural component contributes to this activity. The annotation is appropriate with contributes_to semantics implied. - term: id: GO:1902600 label: proton transmembrane transport evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: involved_in review: summary: IEA from InterPro; consistent with IBA and IGI evidence for proton transport role. action: ACCEPT reason: Proton transmembrane transport is the core function. Multiple lines of evidence support this annotation. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:32296183 qualifier: enables review: summary: Generic protein binding from high-throughput binary interactome; uninformative. action: MARK_AS_OVER_ANNOTATED reason: High-throughput interactome data; protein binding does not capture the specific V0 structural role of e1. - term: id: GO:0005765 label: lysosomal membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-9639286 qualifier: located_in review: summary: Reactome TAS for lysosomal membrane localization; consistent with V0 component localization. action: ACCEPT reason: Lysosomal membrane is the primary functional localization of the assembled V-ATPase V0 domain. - term: id: GO:0005765 label: lysosomal membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-9640167 qualifier: located_in review: summary: Reactome TAS for lysosomal membrane; consistent. action: ACCEPT reason: Lysosomal membrane localization; consistent. - term: id: GO:0005765 label: lysosomal membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-9640168 qualifier: located_in review: summary: Reactome TAS for lysosomal membrane; consistent. action: ACCEPT reason: Lysosomal membrane localization; consistent. - term: id: GO:0005765 label: lysosomal membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-9640175 qualifier: located_in review: summary: Reactome TAS for lysosomal membrane; consistent. action: ACCEPT reason: Lysosomal membrane localization; consistent. - term: id: GO:0005765 label: lysosomal membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-9640195 qualifier: located_in review: summary: Reactome TAS for lysosomal membrane; consistent. action: ACCEPT reason: Lysosomal membrane localization; consistent. - term: id: GO:0005765 label: lysosomal membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-9645598 qualifier: located_in review: summary: Reactome TAS for lysosomal membrane; consistent. action: ACCEPT reason: Lysosomal membrane localization; consistent. - term: id: GO:0005765 label: lysosomal membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-9645608 qualifier: located_in review: summary: Reactome TAS for lysosomal membrane; consistent. action: ACCEPT reason: Lysosomal membrane localization; consistent. - term: id: GO:0005765 label: lysosomal membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-9646468 qualifier: located_in review: summary: Reactome TAS for lysosomal membrane; consistent. action: ACCEPT reason: Lysosomal membrane localization; consistent. - term: id: GO:0005765 label: lysosomal membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-9858941 qualifier: located_in review: summary: Reactome TAS for lysosomal membrane in MITF-dependent lysosome biogenesis context; consistent. action: ACCEPT reason: Lysosomal membrane localization consistent with V0 domain subunit function. - term: id: GO:0046961 label: proton-transporting ATPase activity, rotational mechanism evidence_type: IGI original_reference_id: PMID:17350184 qualifier: enables review: summary: IGI evidence from yeast complementation showing both e1 and e2 are essential for proton pump function; supports ATPase rotational mechanism activity. action: ACCEPT reason: Blake-Palmer et al. 2007 showed that either e1 or e2 can complement yeast lacking the e subunit ortholog, directly demonstrating the essential role of the e subunit in proton pump function. This is valid IGI evidence. supported_by: - reference_id: PMID:17350184 supporting_text: complementation studies in a yeast strain deficient for the ortholog of this subunit, that either form of the e-subunit is essential for proper proton pump function - term: id: GO:1902600 label: proton transmembrane transport evidence_type: IGI original_reference_id: PMID:17350184 qualifier: involved_in review: summary: IGI evidence from yeast complementation; same rationale as GO:0046961 IGI above. action: ACCEPT reason: Yeast complementation study directly demonstrates the e subunit is essential for proton pump function (PMID:17350184). IGI annotation is well supported. supported_by: - reference_id: PMID:17350184 supporting_text: complementation studies in a yeast strain deficient for the ortholog of this subunit, that either form of the e-subunit is essential for proper proton pump function - term: id: GO:0016241 label: regulation of macroautophagy evidence_type: NAS original_reference_id: PMID:22982048 qualifier: involved_in review: summary: NAS annotation; cited paper uses V-ATPase disruption as a tool to impair lysosomal function. Does not specifically implicate e1 subunit in macroautophagy regulation. action: MARK_AS_OVER_ANNOTATED reason: The cited paper does not demonstrate that ATP6V0E1 specifically regulates macroautophagy; it uses generic V-ATPase disruption to block lysosomal activity. This is an over-annotation of a generic downstream consequence of V-ATPase disruption. - term: id: GO:0030670 label: phagocytic vesicle membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-1222516 qualifier: located_in review: summary: Reactome TAS for phagocytic vesicle membrane (intraphagosomal pH lowering context); consistent with V0 domain at phagocytic vesicles in immune cells. action: KEEP_AS_NON_CORE reason: Phagocytic vesicle membrane localization is a non-core context for this ubiquitous V0 subunit. The primary core localizations are lysosomal and endosomal membranes. - term: id: GO:0010008 label: endosome membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-5252133 qualifier: located_in review: summary: Reactome TAS for endosome membrane; consistent with V0 component at endosomal membranes where V-ATPase acidifies endosomes. action: ACCEPT reason: Endosomal membrane localization is a core location for the V-ATPase V0 domain; required for endosomal acidification and receptor recycling. - term: id: GO:0010008 label: endosome membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-74723 qualifier: located_in review: summary: Reactome TAS for endosome membrane in endosome acidification context; consistent. action: ACCEPT reason: Endosome membrane localization; consistent with V-ATPase function. - term: id: GO:0010008 label: endosome membrane evidence_type: TAS original_reference_id: Reactome:R-HSA-917841 qualifier: located_in review: summary: Reactome TAS for endosome membrane in transferrin acidification context; consistent. action: ACCEPT reason: Endosome membrane localization in transferrin endocytosis context; consistent with V-ATPase function. - term: id: GO:0007035 label: vacuolar acidification evidence_type: ISS original_reference_id: GO_REF:0000024 qualifier: involved_in review: summary: ISS manual ortholog transfer; vacuolar acidification is the core downstream function of V-ATPase activity. action: ACCEPT reason: Vacuolar acidification is the primary biological process driven by the V-ATPase. As a required V0 structural subunit, e1 is appropriately annotated to this process. - term: id: GO:0042625 label: ATPase-coupled ion transmembrane transporter activity evidence_type: ISS original_reference_id: GO_REF:0000024 qualifier: enables review: summary: ISS manual ortholog transfer; ATPase-coupled ion transmembrane transporter activity is an appropriate broader molecular function term for the V-ATPase proton translocation activity. action: ACCEPT reason: ATPase-coupled ion transmembrane transporter activity describes the complex-level molecular function that e1 contributes to as a V0 structural component. Appropriate with contributes_to semantics. - term: id: GO:0046961 label: proton-transporting ATPase activity, rotational mechanism evidence_type: TAS original_reference_id: PMID:9556572 qualifier: enables review: summary: TAS from Ludwig et al. 1998 original characterization of M9.2 (e1) protein in bovine V-ATPase; establishes e1 as a V-ATPase membrane sector component with rotational proton transport activity. action: ACCEPT reason: The original characterization paper identified M9.2 (e1) as a V-ATPase membrane sector component, supporting proton-transporting ATPase activity annotation. The e subunit is part of the V0 sector responsible for proton translocation. supported_by: - reference_id: PMID:9556572 supporting_text: M9.2, a novel extremely hydrophobic 9.2-kDa protein comprising 80 amino acids, was detected in the membrane sector - term: id: GO:1902600 label: proton transmembrane transport evidence_type: TAS original_reference_id: PMID:9556572 qualifier: involved_in review: summary: TAS from original M9.2 characterization; proton transmembrane transport is the core function. action: ACCEPT reason: The original characterization places e1 (M9.2) in the V-ATPase membrane sector responsible for proton transport. supported_by: - reference_id: PMID:9556572 supporting_text: M9.2, a novel extremely hydrophobic 9.2-kDa protein comprising 80 amino acids, was detected in the membrane sector references: - id: GO_REF:0000002 title: Gene Ontology annotation through association of InterPro records with GO terms findings: [] - id: GO_REF:0000024 title: Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity findings: [] - id: GO_REF:0000033 title: Annotation inferences using phylogenetic trees findings: [] - id: GO_REF:0000044 title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt findings: [] - id: PMID:17350184 title: 'Molecular cloning and characterization of a novel form of the human vacuolar H+-ATPase e-subunit: an essential proton pump component.' findings: - statement: e1 subunit is ubiquitously expressed; e2 is restricted to kidney/brain; either isoform complements yeast e subunit deletion confirming essential role in proton pump function. - id: PMID:22982048 title: Lipofuscin is formed independently of macroautophagy and lysosomal activity in stress-induced prematurely senescent human fibroblasts. findings: - statement: V-ATPase disruption used as tool to impair lysosomal activity; does not specifically implicate e1 subunit in macroautophagy regulation. - id: PMID:32296183 title: A reference map of the human binary protein interactome. findings: [] - id: PMID:33065002 title: Structures of a Complete Human V-ATPase Reveal Mechanisms of Its Assembly. findings: - statement: >- Cryo-EM structure directly identifies subunit e1 in V0 complex; N-linked glycan at Asn70 experimentally confirmed; V0 contains subunit a, c9c'', d, e, f, and accessory subunits ATP6AP1, ATP6AP2. - id: PMID:9556572 title: Identification and characterization of a novel 9.2-kDa membrane sector-associated protein of vacuolar proton-ATPase from chromaffin granules. findings: - statement: M9.2 (e1 subunit) identified in V-ATPase membrane sector from bovine chromaffin granules; extremely hydrophobic dual-TM protein; 9.2 kDa, 80 amino acids. - id: Reactome:R-HSA-1222516 title: Intraphagosomal pH is lowered to 5 by V-ATPase findings: [] - id: Reactome:R-HSA-5252133 title: ATP6AP1 binds V-ATPase findings: [] - id: Reactome:R-HSA-74723 title: Endosome acidification findings: [] - id: Reactome:R-HSA-917841 title: Acidification of Tf:TfR1 containing endosome findings: [] - id: Reactome:R-HSA-9639286 title: RRAGC,D exchanges GTP for GDP findings: [] - id: Reactome:R-HSA-9640167 title: RRAGA,B exchanges GDP for GTP findings: [] - id: Reactome:R-HSA-9640168 title: >- v-ATPase:Ragulator:RRAGA,B:GTP:RRAGC,D:GDP:SLC38A9:Arginine dissociates yielding v-ATPase:Ragulator:RRAGA,B:GTP:RRAGC,D:GDP and SLC38A9:Arginine findings: [] - id: Reactome:R-HSA-9640175 title: v-ATPase:Ragulator:RagA,B:GDP:RagC,D:GDP binds SLC38A9:Arginine findings: [] - id: Reactome:R-HSA-9640195 title: RRAGA,B hydrolyzes GTP findings: [] - id: Reactome:R-HSA-9645598 title: RRAGC,D hydrolyzes GTP findings: [] - id: Reactome:R-HSA-9645608 title: v-ATPase:Ragulator:RRAGA,B:GTP:RRAGC,D:GDP binds mTORC1 findings: [] - id: Reactome:R-HSA-9646468 title: mTORC1 binds RHEB:GTP findings: [] - id: Reactome:R-HSA-9858941 title: MITF-M-dependent ATP6V0E1 gene expression findings: [] core_functions: - description: >- ATP6V0E1 is a structural dual-transmembrane subunit of the V0 proton-translocation domain of the V-ATPase. The e1 subunit is required for proper proton pump function and is part of the V0 complex at lysosomal and endosomal membranes. Its N-linked glycan at Asn70 contributes to V-ATPase assembly and stability. The e subunit is essential for V-ATPase activity, as demonstrated by yeast complementation studies. contributes_to_molecular_function: id: GO:0046961 label: proton-transporting ATPase activity, rotational mechanism molecular_function: id: GO:0005198 label: structural molecule activity directly_involved_in: - id: GO:1902600 label: proton transmembrane transport - id: GO:0007035 label: vacuolar acidification locations: - id: GO:0005765 label: lysosomal membrane - id: GO:0010008 label: endosome membrane supported_by: - reference_id: file:human/ATP6V0E1/ATP6V0E1-uniprot.txt supporting_text: The proton translocation complex V0 consists of the proton transport subunit a, a ring of proteolipid subunits c9c'', rotary subunit d, subunits e and f, and the accessory subunits ATP6AP1/Ac45 and ATP6AP2/PRR - reference_id: PMID:17350184 supporting_text: complementation studies in a yeast strain deficient for the ortholog of this subunit, that either form of the e-subunit is essential for proper proton pump function suggested_questions: - question: What is the precise structural function of the e subunit within the V0 complex — does it contribute to c-ring stability, the a subunit interface, or the assembly pathway of V0? experts: - Wang L - Rubinstein JL - question: Does the N-linked glycan on Asn70 of e1 have a specific structural role (as part of the luminal glycan coat) in V-ATPase folding or targeting, and does loss of this glycosylation site affect V-ATPase function or localization? experts: - Wang L - Fu TM suggested_experiments: - hypothesis: The N-linked glycan at Asn70 of ATP6V0E1 is required for efficient V-ATPase assembly or lysosomal targeting. description: >- Generate ATP6V0E1 Asn70Gln (N70Q) glycosylation-null mutant by CRISPR/HDR and assess V-ATPase holoenzyme assembly, lysosomal membrane targeting, and lysosomal acidification function compared to wild-type cells. experiment_type: CRISPR knock-in and V-ATPase assembly/acidification assay - hypothesis: ATP6V0E1 (e1) and ATP6V0E2 (e2) confer different targeting or functional properties to V-ATPase complexes in the same cell type. description: >- Using isoform-specific antibodies or endogenous tagging of each paralog in the same cell line, determine whether e1- and e2-containing V-ATPase complexes have distinct subcellular distributions (lysosomal vs endosomal vs plasma membrane) and whether V1/V0 assembly stoichiometry differs between the isoforms. experiment_type: isoform-specific localization and V-ATPase complex stoichiometry