id: Q96A05 gene_symbol: ATP6V1E2 product_type: PROTEIN status: COMPLETE taxon: id: NCBITaxon:9606 label: Homo sapiens description: ATP6V1E2 encodes the testis/sperm-enriched isoform of subunit E of the peripheral V1 sector of the vacuolar-type H(+)-ATPase (V-ATPase), a rotary proton pump. The V-ATPase comprises a cytoplasmic V1 complex that hydrolyzes ATP and a membrane-integral V0 complex that translocates protons across the membrane. Within V1, subunit E pairs with subunit G to form the EG heterodimers that constitute the three peripheral (stator) stalks. These stalks hold the (AB)3 catalytic head stationary against the torque generated when the central D/F rotor turns, coupling ATP hydrolysis in V1 to proton translocation through V0. ATP6V1E2 is the tissue-restricted paralog of the ubiquitously expressed ATP6V1E1; it is enriched in testis and sperm, where a V-ATPase containing this subunit is plausibly associated with the acrosome (a lysosome-related organelle). Its core molecular role is as a structural V1 peripheral-stalk component that enables ATP hydrolysis-driven, rotary proton transport, contributing to acidification of 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: Phylogenetic (IBA) annotation that subunit E of V-ATPase participates in proton transmembrane transport. This is the central biological process for the V-ATPase complex and is the core function of this subunit, which forms part of the EG peripheral stalk required for the rotary pumping mechanism. action: ACCEPT reason: The V-ATPase, of which subunit E is an obligate structural component, hydrolyzes ATP to drive proton translocation across membranes. This IBA annotation correctly captures the core biological role of the gene product. - term: id: GO:0046961 label: proton-transporting ATPase activity, rotational mechanism evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: enables review: summary: Phylogenetic (IBA) annotation to the rotary proton-transporting ATPase molecular function. Subunit E does not itself hydrolyze ATP, but as part of the EG stator stalks it is an essential structural component of the holoenzyme that enables this activity; GO annotates subunits of the complex to the complex activity. action: ACCEPT reason: Subunit E is required for the rotary mechanism by anchoring the catalytic head; annotating the subunit with the complex molecular function follows GO convention for obligate complex members and represents the core function. - term: id: GO:0033178 label: proton-transporting two-sector ATPase complex, catalytic domain evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: part_of review: summary: InterPro-based (IPR002842, V-ATPase V1 E subunit) annotation placing ATP6V1E2 in the catalytic (V1) domain of the two-sector ATPase complex. The V1 sector is the ATP-hydrolyzing catalytic domain of the V-ATPase, and subunit E is a component of it. action: ACCEPT reason: Subunit E is part of the V1 (catalytic) sector of the V-ATPase, so this complex-membership annotation correctly captures the cellular-component context and is consistent with the curated complex membership documented in UniProt. supported_by: - reference_id: file:human/ATP6V1E2/ATP6V1E2-uniprot.txt supporting_text: The V1 complex consists of three catalytic AB heterodimers that form a heterohexamer, three peripheral stalks each consisting of EG heterodimers, one central rotor including subunits D and F, and the regulatory subunits C and H. - term: id: GO:0046961 label: proton-transporting ATPase activity, rotational mechanism evidence_type: IEA original_reference_id: GO_REF:0000120 qualifier: enables review: summary: Electronic (IEA) annotation to the rotary proton-transporting ATPase activity, duplicating the more authoritative IBA annotation of the same term. action: MARK_AS_OVER_ANNOTATED reason: This IEA annotation is redundant with the IBA annotation to the identical term (GO:0046961). The IBA version is retained as the representative core annotation; the duplicate IEA adds no information. - term: id: GO:1902600 label: proton transmembrane transport evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: involved_in review: summary: InterPro-based electronic (IEA) annotation to proton transmembrane transport, duplicating the more authoritative IBA annotation of the same term. action: MARK_AS_OVER_ANNOTATED reason: This IEA annotation is redundant with the IBA annotation to the identical term (GO:1902600). The IBA version is retained as the representative core annotation; the duplicate IEA adds no information. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:21516116 qualifier: enables review: summary: High-throughput next-generation-sequencing interactome screen reporting a binary interaction (with ATP6V1G1, O75348). The E-G interaction is biologically expected since the V1 peripheral stalk is an E-G heterodimer, but the bare 'protein binding' term is uninformative as a molecular-function statement. action: MARK_AS_OVER_ANNOTATED reason: GO:0005515 'protein binding' conveys no specific functional information. The underlying E-G heterodimer relationship is already captured by the V1-complex membership annotation (GO:0033178). - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:25416956 qualifier: enables review: summary: Proteome-scale binary interactome map (Rolland et al.) reporting interactions (with ATP6V1G1, O75348, and BBLN, Q9BUW7) from a high-throughput yeast two-hybrid screen. Bare 'protein binding' is uninformative. action: MARK_AS_OVER_ANNOTATED reason: GO:0005515 'protein binding' conveys no specific molecular function. The meaningful E-G interaction is already represented by complex-membership annotations. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:30021884 qualifier: enables review: summary: Crosslinking mass-spectrometry study of histone interaction landscapes in intact nuclei, reporting an interaction with ATP6V1G1 (O75348) as part of a large-scale dataset. Bare 'protein binding' is uninformative and the study is not focused on ATP6V1E2 function. action: MARK_AS_OVER_ANNOTATED reason: GO:0005515 'protein binding' conveys no specific molecular function and derives from a high-throughput dataset unrelated to the specific role of this subunit. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:32296183 qualifier: enables review: summary: HuRI reference binary interactome (Luck et al.) reporting interactions (with RASSF10 A6NK89, ATP6V1G1 O75348, ATP6V1G2 O95670, and MESD Q14696) from a high-throughput yeast two-hybrid screen. Bare 'protein binding' is uninformative. action: MARK_AS_OVER_ANNOTATED reason: GO:0005515 'protein binding' conveys no specific molecular function. The E-G interactions (ATP6V1G1/G2) reflect expected V1 stalk architecture already captured by complex-membership annotations. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:40205054 qualifier: enables review: summary: Multimodal cell-mapping study (Schaffer et al.) reporting an interaction with ATP6V1G2 (O95670) from a high-throughput dataset. Bare 'protein binding' is uninformative as a molecular-function statement. action: MARK_AS_OVER_ANNOTATED reason: GO:0005515 'protein binding' conveys no specific molecular function. The E-G interaction is already represented by complex-membership annotations. - term: id: GO:0001669 label: acrosomal vesicle evidence_type: IEA original_reference_id: GO_REF:0000107 qualifier: located_in review: summary: Ensembl-orthology electronic annotation transferred from mouse Atp6v1e2 (Q9D593) placing the protein in the acrosomal vesicle. The acrosome is a lysosome-related organelle in sperm, and V-ATPase-mediated acidification there is biologically plausible for this testis/sperm-enriched isoform, but the localization has not been directly demonstrated for the human protein. action: KEEP_AS_NON_CORE reason: Plausible and consistent with the testis/sperm-enriched expression of ATP6V1E2, but supported only by orthology-based IEA without direct human experimental evidence; retained as a non-core localization. - term: id: GO:0016241 label: regulation of macroautophagy evidence_type: NAS original_reference_id: PMID:22982048 qualifier: involved_in review: summary: NAS (non-traceable author statement) annotation derived from a study of lipofuscin formation in stress-induced senescent fibroblasts. The paper concerns macroautophagy and lysosomal activity in fibroblasts and does not study the testis-specific ATP6V1E2 isoform. Any V-ATPase role in autophagy is an indirect downstream consequence of lysosomal acidification. action: MARK_AS_OVER_ANNOTATED reason: The annotation is NAS without a traceable experimental link to this isoform; macroautophagy regulation is not a core function of this testis-restricted V1 stalk subunit and is at best an indirect consequence of organelle acidification. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-1222516 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol. The V1 sector is cytoplasmic/peripheral, so 'cytosol' is defensible, but it is a coarse location that fails to capture the V-ATPase-complex / organelle-membrane functional context. action: KEEP_AS_NON_CORE reason: Defensible but coarse; the V1 subunit is peripheral/cytoplasmic, yet the functionally informative location is the V-ATPase complex on intracellular membranes. Retained as non-core. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-5252133 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-74723 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-917841 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-9639286 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-9640167 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-9640168 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-9640175 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-9640195 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-9645598 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-9645608 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. - term: id: GO:0005829 label: cytosol evidence_type: TAS original_reference_id: Reactome:R-HSA-9646468 qualifier: located_in review: summary: Reactome reaction-level TAS annotation to cytosol, duplicating other Reactome cytosol annotations for this gene. action: KEEP_AS_NON_CORE reason: Defensible but coarse and redundant with other Reactome cytosol annotations; the informative location is the V-ATPase complex on membranes. core_functions: - description: Structural component of the V1 peripheral (stator) stalk of the vacuolar H(+)-ATPase, forming an EG heterodimer that anchors the (AB)3 catalytic head and enables ATP hydrolysis-driven rotary proton transport supported_by: - reference_id: file:human/ATP6V1E2/ATP6V1E2-uniprot.txt supporting_text: The V1 complex consists of three catalytic AB heterodimers that form a heterohexamer, three peripheral stalks each consisting of EG heterodimers, one central rotor including subunits D and F, and the regulatory subunits C and H. molecular_function: id: GO:0046961 label: proton-transporting ATPase activity, rotational mechanism directly_involved_in: - id: GO:1902600 label: proton transmembrane transport in_complex: id: GO:0033178 label: proton-transporting two-sector ATPase complex, catalytic domain proposed_new_terms: [] suggested_questions: - question: Is the V-ATPase complex containing ATP6V1E2 specifically localized to the sperm acrosome, and does it acidify the acrosomal lumen during spermatogenesis or the acrosome reaction? - question: Does ATP6V1E2 functionally substitute for ATP6V1E1 within the same V-ATPase holoenzyme in testis, or do the two paralogs assemble into distinct, tissue-specific V-ATPase populations? - question: Does loss of ATP6V1E2 cause a male-fertility or sperm-function phenotype distinct from that of the ubiquitous ATP6V1E1? suggested_experiments: - description: Immunolocalization (and immuno-EM) of ATP6V1E2 in human/mouse testis and spermatozoa to confirm acrosomal-vesicle localization and distinguish it from ATP6V1E1. - description: Reconstitution or co-immunoprecipitation assays to test EG heterodimer formation of ATP6V1E2 with ATP6V1G1/G2 and incorporation into an assembled, ATP-hydrolyzing V-ATPase complex. - description: Generation and phenotyping of an Atp6v1e2 knockout (sperm count, motility, acrosome reaction, acrosomal pH, fertility) to define its in vivo role. references: - id: GO_REF:0000002 title: Gene Ontology annotation through association of InterPro records with GO terms findings: [] - id: GO_REF:0000033 title: Annotation inferences using phylogenetic trees findings: [] - id: GO_REF:0000107 title: Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara findings: [] - id: GO_REF:0000120 title: Combined Automated Annotation using Multiple IEA Methods findings: [] - id: PMID:12036578 title: A human gene, ATP6E1, encoding a testis-specific isoform of H(+)-ATPase subunit E. findings: - statement: ATP6V1E2 (ATP6E1) encodes a testis-specific isoform of the V-ATPase subunit E, distinct from the ubiquitous ATP6V1E1 paralog. reference_section_type: ABSTRACT - id: PMID:21516116 title: Next-generation sequencing to generate interactome datasets. findings: [] - id: PMID:22982048 title: Lipofuscin is formed independently of macroautophagy and lysosomal activity in stress-induced prematurely senescent human fibroblasts. findings: [] - id: PMID:25416956 title: A proteome-scale map of the human interactome network. findings: [] - id: PMID:30021884 title: Histone Interaction Landscapes Visualized by Crosslinking Mass Spectrometry in Intact Cell Nuclei. findings: [] - id: PMID:32296183 title: A reference map of the human binary protein interactome. findings: [] - id: PMID:40205054 title: Multimodal cell maps as a foundation for structural and functional genomics. findings: [] - 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: []