ATP6V0B: The c'' Proteolipid Subunit of Vacuolar H⁺-ATPase

Introduction

ATP6V0B (also known as ATP6F) encodes the c'' subunit of the V₀ membrane sector of vacuolar H⁺-ATPase (V-ATPase), a multi-subunit enzyme responsible for the acidification of intracellular compartments in all eukaryotic cells. The gene product is a 21 kDa proteolipid that forms part of the proton-conducting pore of V-ATPase, participating directly in the translocation of protons across membranes. V-ATPase activity is essential for maintaining the acidic pH of lysosomes, endosomes, the trans-Golgi network, and secretory vesicles, and plays critical roles in processes including protein degradation, receptor-mediated endocytosis, autophagy, neurotransmitter loading, and nutrient sensing[stevens-1997-vatpase-review-abstract].

The human ATP6V0B gene was first cloned and characterized by Nishigori and colleagues in 1998, who identified it as a homolog of the Saccharomyces cerevisiae VMA16 protein[nishigori-1998-atp6f-abstract]. The gene maps to chromosome 1p32.3 and encodes a highly hydrophobic protein of 205 amino acids with five predicted transmembrane domains. A critical glutamic acid residue (Glu98) within the fourth transmembrane segment is essential for proton transport activity[nishigori-1998-atp6f-abstract]. While V-ATPase has long been considered a housekeeping enzyme required for basic cellular functions, recent research has revealed that ATP6V0B expression is dynamically regulated and plays specific roles in cellular signaling pathways, particularly the mTORC1 pathway controlling cell growth and autophagy.

V-ATPase Complex Structure and Organization

The V-ATPase holoenzyme is a rotary motor that couples ATP hydrolysis to proton pumping across membranes. It consists of two functional domains: a cytoplasmic V₁ sector (~500 kDa) responsible for ATP hydrolysis, and a membrane-embedded V₀ sector (~250 kDa) that forms the proton-conducting pore[stevens-1997-vatpase-review-abstract]. The V₁ sector contains eight different subunits (A-H) arranged in an A₃B₃CDE₃FG₃H structure, with the catalytic sites located at the interfaces between the A and B subunits. The V₀ sector in mammals consists of multiple subunits including the 116 kDa subunit a (with tissue-specific isoforms a1-a4), the proteolipid subunits c, c', and c'', subunit d, and subunit e[stevens-1997-vatpase-review-abstract].

The proteolipid subunits (c, c', and c'') are the key components of the proton-conducting rotor ring. Unlike bacterial and archaeal V-type ATPases which have homo-oligomeric c-rings, eukaryotic V-ATPases possess hetero-oligomeric rings composed of multiple c subunit isoforms[zhao-2015-cryo-em-vatpase-abstract]. Cryo-electron microscopy studies of the yeast V-ATPase revealed that the c-ring contains 10 proteolipid subunits arranged in a ring structure[zhao-2015-cryo-em-vatpase-abstract]. This stoichiometry establishes the ATP:H⁺ ratio for proton pumping at 3:10, meaning that hydrolysis of three ATP molecules is coupled to the translocation of ten protons across the membrane[zhao-2015-cryo-em-vatpase-abstract].

ATP6V0B as the c'' Proteolipid Subunit

ATP6V0B encodes the c'' isoform of the V-ATPase proteolipid. The human c'' protein is 205 amino acids in length and shares 61% amino acid identity and 83% similarity with the yeast Vma16p protein[nishigori-1998-atp6f-abstract]. The mouse ortholog, characterized by Sun-Wada and colleagues, exhibits 83-84% similarity to both yeast Vma16p and Caenorhabditis elegans vha-4, indicating strong evolutionary conservation of this subunit across eukaryotes[sun-wada-2001-mouse-atp6f-abstract].

Structural analysis predicts five transmembrane α-helical segments in ATP6V0B, similar to other c-type proteolipids[nishigori-1998-atp6f-abstract]. A critical feature is the conserved glutamic acid residue (Glu98 in humans) located in the middle of the fourth transmembrane helix, which serves as the proton-binding site during transport[nishigori-1998-atp6f-abstract]. Mutation of this glutamate abolishes proton pumping activity, establishing it as essential for the catalytic function of the enzyme. The high-resolution cryo-EM structure of the yeast V₀ sector at 3.5 Å resolution revealed the precise arrangement of amino acids constituting the proton pathway at the interface between the proteolipid ring and subunit a[roh-2018-v0-structure-abstract].

The genomic organization of ATP6V0B is conserved between human and mouse, with both genes consisting of 8 exons separated by 7 introns that follow the GT-AG splicing rule[sun-wada-2001-mouse-atp6f-abstract]. The gene is transcribed as two mRNA species of approximately 1.0 and 1.8 kb in multiple tissues, with varying expression levels suggesting tissue-specific regulation[sun-wada-2001-mouse-atp6f-abstract].

Mechanism of Proton Translocation

The V-ATPase operates as a rotary motor in which ATP hydrolysis in the V₁ sector drives the rotation of the central rotor subcomplex, which is mechanically coupled to the proteolipid c-ring in V₀. As the c-ring rotates against the stationary subunit a, protons are picked up from the cytoplasmic side of the membrane and released into the luminal side through a two-channel mechanism.

Each proteolipid subunit carries a single proton on its essential glutamate residue. On the cytoplasmic side, protons enter through a half-channel in subunit a and bind to the glutamate of an incoming c-subunit. The c-ring then rotates, carrying the protonated glutamate through the hydrophobic core of the membrane. On completing nearly a full rotation, the protonated glutamate encounters a second half-channel in subunit a opening to the luminal side, where the proton is released. The cryo-EM structures of yeast V-ATPase in three rotational states provided direct visualization of the conformational changes that occur during this rotary catalytic cycle[zhao-2015-cryo-em-vatpase-abstract].

Subcellular Localization and Membrane Targeting

ATP6V0B, as part of the V-ATPase complex, localizes to the membranes of multiple acidic intracellular compartments. Studies with epitope-tagged constructs demonstrated localization to endomembrane organelles including the endoplasmic reticulum, Golgi apparatus, endosomes, and lysosomes[sun-wada-2001-mouse-atp6f-abstract]. The specific localization of V-ATPase is largely determined by the isoform of the subunit a that is incorporated into the complex. In yeast, the Vph1p isoform targets V-ATPase to the vacuole, while the Stv1p isoform targets it to the late Golgi and endosomes[finnigan-2011-vatpase-isoforms-abstract]. Similarly, in mammals, different a-subunit isoforms (a1-a4) direct V-ATPase to specific cellular locations including lysosomes, the Golgi, synaptic vesicles, and the plasma membrane of specialized cells.

V-ATPase is assembled in the endoplasmic reticulum through a complex pathway requiring dedicated assembly factors. The V₀ sector assembles first, requiring factors including Vma21p (TMEM199 in humans) and Voa1p[roh-2018-v0-structure-abstract]. Remarkably, the high-resolution structure of yeast V₀ revealed that the C-terminus of the assembly factor Voa1 remains as an integral component of the mature complex, with its transmembrane helix bound inside the proteolipid ring contributing to complex stability[roh-2018-v0-structure-abstract].

Biological Processes and Cellular Pathways

Lysosomal Acidification and Autophagy

The primary function of V-ATPase containing ATP6V0B is the acidification of intracellular compartments. Lysosomal acidification to pH 4.5-5.0 is essential for the activity of acid hydrolases that degrade macromolecules during autophagy and endocytosis. V-ATPase inhibition leads to accumulation of undigested material, disruption of autophagy, and cell death[stevens-1997-vatpase-review-abstract].

mTORC1 Signaling and Amino Acid Sensing

A groundbreaking discovery by Zoncu and colleagues demonstrated that V-ATPase is essential for amino acid activation of mTORC1, the master regulator of cell growth[zoncu-2011-mtorc1-vatpase-abstract]. The V-ATPase engages in amino acid-sensitive interactions with the Ragulator complex, which anchors the Rag GTPases to the lysosomal surface. In the presence of amino acids, V-ATPase activity promotes the interaction between Ragulator and the Rag heterodimers, leading to mTORC1 recruitment to the lysosome where it is activated by the GTPase Rheb[zoncu-2011-mtorc1-vatpase-abstract][bar-peled-2012-ragulator-gef-abstract]. This "inside-out" mechanism suggests that amino acids are sensed within the lysosomal lumen, with the signal transmitted through V-ATPase to activate mTORC1 on the cytoplasmic surface[zoncu-2011-mtorc1-vatpase-abstract].

E2F1 Transcriptional Regulation

A significant finding by Meo-Evoli and colleagues identified ATP6V0B as a direct transcriptional target of the E2F1 transcription factor[meo-evoli-2015-e2f1-vatpase-abstract]. Chromatin immunoprecipitation assays confirmed E2F1 binding to the ATP6V0B promoter, and E2F1 activation led to increased ATP6V0B mRNA expression. Importantly, ectopic expression of ATP6V0B alone was sufficient to increase V-ATPase activity and mTORC1 signaling, while ATP6V0B knockdown abrogated E2F1-induced mTORC1 activation[meo-evoli-2015-e2f1-vatpase-abstract]. This pathway links E2F1-driven cell cycle progression to V-ATPase activity and mTORC1-dependent cell growth, with implications for understanding the metabolic reprogramming in proliferating and cancer cells.

Thyroid Hormone-Induced Expression

Thyroid hormone (T3) has been identified as a regulator of V-ATPase subunit expression, including ATP6V0B[tseng-2023-thyroid-hormone-abstract]. Tseng and colleagues demonstrated that T3 activates expression of numerous lysosomal genes in a thyroid hormone receptor-dependent manner, including ATP6V0B, ATP6V0D1, and ATP6V1E1. This hormonal regulation links V-ATPase expression to metabolic state, as thyroid hormone promotes lysosomal biogenesis and autophagy during periods of increased metabolic demand. The T3-induced upregulation of V-ATPase components enhances lysosomal function, facilitating the breakdown of lipids and other macromolecules during autophagy[tseng-2023-thyroid-hormone-abstract].

Neurosecretion and Membrane Fusion

Beyond its role in acidification, the V₀ sector has been implicated in membrane fusion events independent of proton pumping. In synaptic vesicles, V-ATPase acidification is required for neurotransmitter loading, but studies suggest V₀ may also directly participate in vesicle fusion with the plasma membrane[morel-2015-neurosecretion-abstract]. V₀ interacts with SNARE proteins and calmodulin, and perturbation of these interactions affects neurotransmitter release. The V₀ sector may function as a pH sensor that regulates SNARE complex assembly during vesicle priming and may contribute to fusion pore formation and stability[morel-2015-neurosecretion-abstract].

Disease Associations and Clinical Relevance

Cancer

Overexpression of ATP6V0B has been associated with tumor progression in multiple cancer types. In bladder cancer, ATP6V0B is overexpressed and correlates with poor patient prognosis[wang-2025-bladder-cancer-abstract]. Functional studies demonstrated that ATP6V0B promotes proliferation, invasion, and migration of bladder cancer cells, while knockdown inhibits tumor growth in vivo. Mechanistically, ATP6V0B activates PI3K/AKT signaling through upregulation of PAQR4[wang-2025-bladder-cancer-abstract]. ATP6V0B has also been identified as a potential biomarker for pancreatic cancer in extracellular vesicle-based liquid biopsy approaches[greenberg-2025-pancreatic-ev-abstract]. Additionally, ATP6V0B expression has been associated with cellular senescence phenotypes in hepatocellular carcinoma and has been identified as a hub gene in osteomyelitis-associated programmed cell death pathways.

Pigmentation and Neurofibromatosis Type 1

Genetic studies have linked ATP6V0B variants to pigmentation phenotypes. In patients with Neurofibromatosis type 1 (NF1), SNPs near the ATP6V0B locus (rs4660761 and rs7161) were significantly associated with café-au-lait macule count[pemov-2014-nf1-calm-abstract]. These SNPs are predicted to regulate ATP6V0B expression, and the association suggests a role for V-ATPase in melanosome biology and skin pigmentation[pemov-2014-nf1-calm-abstract]. Studies comparing melanocytes from individuals with dark versus light skin identified ATP6V0B among genes showing differential expression, supporting an evolutionary role in the pigmentary phenotype[lopez-2015-melanocyte-abstract].

V-ATPase Subunit Mutations and Human Disease

While specific pathogenic mutations in ATP6V0B have not been reported, mutations in other V-ATPase subunits cause well-characterized human diseases. Mutations in ATP6V0A3 (a3 subunit) cause autosomal recessive osteopetrosis with neurodegeneration. Mutations in ATP6V0A2 (a2 subunit) cause cutis laxa type II with wrinkly skin syndrome. Mutations in ATP6V1B1 and ATP6V0A4 cause distal renal tubular acidosis with sensorineural deafness[shine-2014-vision-abstract]. The structural and functional conservation of the c'' subunit suggests that damaging mutations would likely be incompatible with life or cause severe developmental abnormalities. Indeed, genetic studies in Drosophila demonstrated that V-ATPase knockout mutations are recessive lethal, with lethal alleles of multiple V-ATPase subunits showing consistent phenotypes including transparent Malpighian tubules[allan-2005-drosophila-vatpase-abstract]. The essential nature of V-ATPase for organismal viability explains the absence of loss-of-function mutations in core subunits like ATP6V0B in human disease databases.

Open Questions

Several important questions remain about ATP6V0B function and regulation:

1. Subunit stoichiometry in mammalian V-ATPase: While the yeast c-ring contains 10 proteolipids, the exact composition and stoichiometry of c, c', and c'' subunits in the mammalian c-ring remains to be definitively established.

2. Tissue-specific functions: Do different expression ratios of the proteolipid isoforms (c, c', c'') confer tissue-specific properties to V-ATPase function?

3. ATP6V0B in cancer progression: What is the precise mechanism by which ATP6V0B overexpression promotes tumor metastasis beyond activation of PI3K/AKT signaling? Does it involve altered lysosomal positioning, enhanced matrix degradation, or other mechanisms?

4. Regulatory mechanisms: Beyond E2F1 regulation, what other transcription factors and signaling pathways control ATP6V0B expression under different physiological conditions?

5. Therapeutic targeting: Can selective modulation of ATP6V0B-containing V-ATPases provide therapeutic benefit in cancer without disrupting essential V-ATPase functions in normal tissues?

6. Non-canonical functions: Does ATP6V0B play direct roles in membrane fusion or other cellular processes independent of its function in the V-ATPase proton pore?

References

• nishigori-1998-atp6f-abstract: Nishigori H, Yamada S, Tomura H, et al. Identification and characterization of the gene encoding a second proteolipid subunit of human vacuolar H(+)-ATPase (ATP6F). Genomics. 1998;50(2):222-8. PMID: 9653649. DOI: 10.1006/geno.1998.5310

• sun-wada-2001-mouse-atp6f-abstract: Sun-Wada GH, Murakami H, Nakai H, et al. Mouse Atp6f, the gene encoding the 23-kDa proteolipid of vacuolar proton translocating ATPase. Gene. 2001;274(1-2):93-9. PMID: 11675001. DOI: 10.1016/s0378-1119(01)00603-5

• izumi-2003-promoter-abstract: Izumi H, Ise T, Murakami T, et al. Structural and functional characterization of two human V-ATPase subunit gene promoters. Biochim Biophys Acta. 2003;1628(2):97-104. PMID: 12890556. DOI: 10.1016/s0167-4781(03)00119-2

• stevens-1997-vatpase-review-abstract: Stevens TH, Forgac M. Structure, function and regulation of the vacuolar (H+)-ATPase. Annu Rev Cell Dev Biol. 1997;13:779-808. PMID: 9442887. DOI: 10.1146/annurev.cellbio.13.1.779

• zhao-2015-cryo-em-vatpase-abstract: Zhao J, Benlekbir S, Rubinstein JL. Electron cryomicroscopy observation of rotational states in a eukaryotic V-ATPase. Nature. 2015;521(7551):241-5. PMID: 25971514. DOI: 10.1038/nature14365

• roh-2018-v0-structure-abstract: Roh SH, Stam NJ, Hryc CF, et al. The 3.5-Å CryoEM Structure of Nanodisc-Reconstituted Yeast Vacuolar ATPase V₀ Proton Channel. Mol Cell. 2018;69(6):993-1004.e3. PMID: 29526695. DOI: 10.1016/j.molcel.2018.02.006

• zoncu-2011-mtorc1-vatpase-abstract: Zoncu R, Bar-Peled L, Efeyan A, et al. mTORC1 senses lysosomal amino acids through an inside-out mechanism that requires the vacuolar H(+)-ATPase. Science. 2011;334(6056):678-83. PMID: 22053050. DOI: 10.1126/science.1207056

• bar-peled-2012-ragulator-gef-abstract: Bar-Peled L, Schweitzer LD, Zoncu R, Sabatini DM. Ragulator is a GEF for the rag GTPases that signal amino acid levels to mTORC1. Cell. 2012;150(6):1196-208. PMID: 22980980. DOI: 10.1016/j.cell.2012.07.032

• meo-evoli-2015-e2f1-vatpase-abstract: Meo-Evoli N, Almacellas E, Massucci FA, et al. V-ATPase: a master effector of E2F1-mediated lysosomal trafficking, mTORC1 activation and autophagy. Oncotarget. 2015;6(29):28057-70. PMID: 26356814. DOI: 10.18632/oncotarget.4812

• morel-2015-neurosecretion-abstract: Morel N, Poëa-Guyon S. The membrane domain of vacuolar H(+)ATPase: a crucial player in neurotransmitter exocytotic release. Cell Mol Life Sci. 2015;72(13):2561-73. PMID: 25795337. DOI: 10.1007/s00018-015-1886-2

• pemov-2014-nf1-calm-abstract: Pemov A, Sung H, Hyland PL, et al. Genetic modifiers of neurofibromatosis type 1-associated café-au-lait macule count identified using multi-platform analysis. PLoS Genet. 2014;10(10):e1004575. PMID: 25329635. DOI: 10.1371/journal.pgen.1004575

• wang-2025-bladder-cancer-abstract: Wang X, Qu Y, Sun Y, et al. ATP6V0B promotes the tumorigenesis of bladder cancer by activating PAQR4/PI3K/AKT signaling. BMC Cancer. 2025;25(1):789. PMID: 40295930. DOI: 10.1186/s12885-025-14183-z

• shine-2014-vision-abstract: Shine L, Kilty C, Gross J, Kennedy B. Vacuolar ATPases and their role in vision. Adv Exp Med Biol. 2014;801:97-103. PMID: 24664686. DOI: 10.1007/978-1-4614-3209-8_13

• lopez-2015-melanocyte-abstract: López S, Smith-Zubiaga I, García de Galdeano A, et al. Comparison of the Transcriptional Profiles of Melanocytes from Dark and Light Skinned Individuals under Basal Conditions and Following Ultraviolet-B Irradiation. PLoS One. 2015;10(8):e0134911. PMID: 26244334. DOI: 10.1371/journal.pone.0134911

• finnigan-2011-vatpase-isoforms-abstract: Finnigan GC, Hanson-Smith V, Houser BD, et al. The reconstructed ancestral subunit a functions as both V-ATPase isoforms Vph1p and Stv1p in Saccharomyces cerevisiae. Mol Biol Cell. 2011;22(17):3176-91. PMID: 21737673. DOI: 10.1091/mbc.E11-03-0244

• greenberg-2025-pancreatic-ev-abstract: Greenberg ZF, Ali S, Brock A, et al. Nanomaterial isolated extracellular vesicles enable high precision identification of tumor biomarkers for pancreatic cancer liquid biopsy. J Nanobiotechnology. 2025;23(1):467. PMID: 40598203. DOI: 10.1186/s12951-025-03527-3

• tseng-2023-thyroid-hormone-abstract: Tseng YT, Lu PY, Lee WJ, et al. Thyroid hormone upregulates ATP6V0B and increases lysosomal function in autophagy. Biochem Biophys Res Commun. 2023;662:66-75. PMID: 37099812. DOI: 10.1016/j.bbrc.2023.04.061

• allan-2005-drosophila-vatpase-abstract: Allan AK, Du J, Davies SA, Bhartiya DP. Genome-wide survey of V-ATPase genes in Drosophila reveals a conserved renal phenotype for lethal alleles. Physiol Genomics. 2005;22(2):128-38. PMID: 15855386. DOI: 10.1152/physiolgenomics.00233.2004

Citations

1. allan-2005-drosophila-vatpase-abstract.md
2. bar-peled-2012-ragulator-gef-abstract.md
3. finnigan-2011-vatpase-isoforms-abstract.md
4. greenberg-2025-pancreatic-ev-abstract.md
5. higashida-2016-atp6v0c-neurotransmitter-abstract.md
6. izumi-2003-promoter-abstract.md
7. lopez-2015-melanocyte-abstract.md
8. meo-evoli-2015-e2f1-vatpase-abstract.md
9. morel-2015-neurosecretion-abstract.md
10. nishigori-1998-atp6f-abstract.md
11. pemov-2014-nf1-calm-abstract.md
12. roh-2018-v0-structure-abstract.md
13. shine-2014-vision-abstract.md
14. stevens-1997-vatpase-review-abstract.md
15. sun-wada-2001-mouse-atp6f-abstract.md
16. tseng-2023-thyroid-hormone-abstract.md
17. wang-2025-bladder-cancer-abstract.md
18. zhao-2015-cryo-em-vatpase-abstract.md
19. zoncu-2011-mtorc1-vatpase-abstract.md

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.

Research plan and verification
Objective 1: Verify identity, organism, family, domains. The target is human ATP6V0B (UniProt Q99437), encoding the V-ATPase V0 21 kDa proteolipid subunit c'' (also called c-double-prime), a member of the V-ATPase proteolipid subunit family. Literature identifies ATP6V0B as the V0 c'' proteolipid subunit in mammals, consistent with the UniProt description and human organism context (Homo sapiens). V-ATPase proteolipids (c, c', c'') are homologous to F-type ATP synthase c subunits and form the membrane c-ring of the Vo sector (ion-conducting rotor), validating the protein family and domain expectations (ATPase proteolipid c-like) (holliday2014vacuolarh+atpasean pages 2-3, cipriano2008structureandregulation pages 2-4, forgac1999structureandproperties pages 3-3).

Objective 2: Summarize key concepts and definitions
- V-ATPase architecture and function: Eukaryotic V-ATPases acidify intracellular organelles and, in specialized cells, the extracellular milieu. They consist of a cytosolic catalytic V1 sector (ATP hydrolysis) and a membrane-embedded Vo sector (H+ translocation). ATP hydrolysis in V1 drives rotation of the central stalk (D/F) and subunit d, which rotates the proteolipid c-ring of Vo past the stationary a-subunit to move protons across the membrane (rotary mechanism) (cipriano2008structureandregulation pages 2-4, holliday2014vacuolarh+atpasean pages 2-3).
- Proteolipid subunits: The Vo proteolipids include c (4 transmembrane helices), c' (4 TM), and c'' (5 TM; ATP6V0B). Each harbors a single buried, protonatable carboxyl essential for H+ translocation: in TM4 of c (and c') and TM3 of c'' (c'') (cipriano2008structureandregulation pages 2-4, forgac1999structureandproperties pages 3-3).
- Compartmental roles: V-ATPases acidify endosomes, lysosomes, Golgi, and secretory/synaptic vesicles; plasma membrane V-ATPases occur in specialized cells (e.g., renal intercalated cells, epididymal clear cells, osteoclast ruffled border), where extracellular acidification supports physiological functions (holliday2014vacuolarh+atpasean pages 2-3, chu2021thevatpasea3 pages 2-3).

Objective 3: ATP6V0B-specific function and structural/biochemical details
- Identity and synonyms: ATP6V0B encodes the Vo proteolipid subunit c'' (c-double-prime), a ~20–23 kDa hydrophobic subunit with five transmembrane helices; it is homologous to other proteolipids and to the F-type c subunit (holliday2014vacuolarh+atpasean pages 2-3, forgac1999structureandproperties pages 3-3).
- Conserved catalytic residue: c'' contains a buried acidic residue in TM3 required for proton translocation; mutational/chemical modification studies demonstrate that neutralizing the essential carboxyl of a single proteolipid subunit can abolish transport, underscoring the functional necessity of each proteolipid’s conserved carboxyl (cipriano2008structureandregulation pages 2-4, forgac1999structureandproperties pages 3-3).
- c-ring composition and stoichiometry: In yeast, the Vo ring contains multiple c copies plus single copies of c' and c'' (a1 d1 e n c4–5 c'1 c''1), establishing a general principle of mixed proteolipid rings. Mammalian summaries similarly describe a c-ring that includes a single c'' together with multiple c subunits; some overviews denote a c9 + c'' ring, implying one ATP6V0B per ring in mammals (cipriano2008structureandregulation pages 2-4, chu2021thevatpasea3 pages 2-3, yang2025vatpaseandlysosomal pages 6-7).
- Placement and interactions: Cross-linking places the a-subunit TM7 adjacent to TM4 of c' and TM3 of c'', consistent with a direct interface between a and proteolipid helices where proton exchange occurs during rotation. Potent macrolide inhibitors (bafilomycin/concanamycin) bind within helical interfaces of the proteolipid ring, indicating druggable grooves near c/c'' interfaces (cipriano2008structureandregulation pages 2-4).

Objective 4: Localization and pathways
- Subcellular localization: ATP6V0B-containing V-ATPases populate the acidifying pumps of the endo-lysosomal system, Golgi, and secretory/synaptic vesicles; in certain polarized or specialized cell types, V-ATPase is targeted to the plasma membrane for extracellular acidification (kidney intercalated cells, epididymis clear cells, osteoclasts). Targeting is largely determined by the isoform of the a-subunit (e.g., a3 targeting in osteoclasts), but the proteolipid ring that includes ATP6V0B is integral to Vo in all locations (holliday2014vacuolarh+atpasean pages 2-3, chu2021thevatpasea3 pages 2-3).
- Pathways: V-ATPases are central for endocytic trafficking, receptor–ligand dissociation, lysosomal hydrolase activation, neurotransmitter loading into synaptic vesicles, autophagy and mTORC1 nutrient/energy sensing at lysosomes. By contributing to luminal acidification, the ATP6V0B-containing c-ring is required for these processes (cipriano2008structureandregulation pages 2-4, holliday2014vacuolarh+atpasean pages 2-3).

Objective 5: Recent developments (priority to 2023–2024) and latest research context
- Although few 2023–2024 primary data directly isolate ATP6V0B-specific effects, contemporary reviews and updates reinforce mechanistic placement of the proteolipid ring and its regulation within emerging V-ATPase biology, including lysosomal energy-sensing platforms and accessory subunits embedded near the c-ring in mammalian brain V-ATPases (e.g., AC45/ATP6AP1, ATP6AP2) (chen2025theemergingroles pages 22-23, yang2025vatpaseandlysosomal pages 6-7). These updates contextualize ATP6V0B as the unique c'' proteolipid in a mammalian c-ring whose stability, interactions, and regulation are relevant to disease pathways.

Objective 6: Regulation and interaction partners
- Transcriptional regulation: The transcription factor E2F1 upregulates ATP6V0B expression and V-ATPase activity; E2F1 activation drives lysosome peripheral trafficking and mTORC1 activation, which is suppressed by V-ATPase inhibition. Reporter assays and mRNA measurements confirm E2F1-induced ATP6V0B transcription (meoevoli2015vatpaseamaster pages 5-8).
- Protein interactions and assembly environment: Mammalian V-ATPases incorporate accessory proteins (ATP6AP1/AC45 and ATP6AP2) within or adjacent to the proteolipid ring in brain complexes, and these proteins interface with mTORC1 energy-sensing machinery, linking Vo ring composition to signaling. Although not specific to ATP6V0B alone, they are positioned in the ring neighborhood where c'' resides (yang2025vatpaseandlysosomal pages 6-7).

Objective 7: Disease associations and phenotypes
- V-ATPase subunits and disease: Multiple V-ATPase subunit mutations cause human disease, particularly neurological disorders (e.g., ATP6V1A variants causing developmental epileptic encephalopathy), emphasizing that disruption of V-ATPase function leads to organelle acidification defects and neurodevelopmental phenotypes. While direct human genetic disease caused by ATP6V0B has not been clearly established, the essential role of the proteolipid ring (including c'') in proton translocation supports the plausibility that perturbation would be deleterious (groszer2022rarehumanatp6v1a pages 7-9, cipriano2008structureandregulation pages 2-4, forgac1999structureandproperties pages 3-3).
- Cancer and tissue remodeling: V-ATPase localization to the plasma membrane in tumor cells and osteoclasts drives extracellular acidification for invasion/metastasis and bone resorption, respectively. ATP6V0B participates as the c'' subunit of the proton-translocating rotor required for these activities (holliday2014vacuolarh+atpasean pages 2-3, chu2021thevatpasea3 pages 2-3).

Objective 8: Applications and implementations
- Pharmacology and tool compounds: Bafilomycin and concanamycin are classical macrolide inhibitors that target interfaces within the proteolipid ring of Vo, inhibiting rotation and H+ translocation. These compounds are widely used as research tools to block organelle acidification, interrogate autophagy (late-stage flux), and inhibit mTORC1 activation dependent on lysosomal acidification (cipriano2008structureandregulation pages 2-4).
- Translational contexts: Accessory subunit interactions near the proteolipid ring (e.g., ATP6AP1/ATP6AP2) link V-ATPase to nutrient/energy sensing (mTORC1), suggesting V-ATPase modulators—and, by extension, the stability/interaction profile of the c-ring that includes ATP6V0B—may have therapeutic implications in cancer and metabolic/inflammatory diseases (yang2025vatpaseandlysosomal pages 6-7, chen2025theemergingroles pages 22-23).

Objective 9: Quantitative/statistical details
- Proteolipid ring stoichiometry: Yeast Vo contains 4–5 copies of c plus single copies of c' and c'' in the ring (a1 d1 e n c4–5 c'1 c''1). Mammalian summaries suggest a similar principle with multiple c-subunits and one c'' per ring (often summarized as c9 + c'') (cipriano2008structureandregulation pages 2-4, chu2021thevatpasea3 pages 2-3, yang2025vatpaseandlysosomal pages 6-7).
- Essential residues: The essential protonatable carboxylates are located in TM4 of c (and c') and TM3 of c''; neutralization or chemical modification of a single proteolipid’s essential carboxyl can abolish proton transport, underscoring the dependence on every proteolipid site within the ring (cipriano2008structureandregulation pages 2-4, forgac1999structureandproperties pages 3-3).

Expert analysis
- Specificity and unique role of ATP6V0B: Among the proteolipid family, ATP6V0B provides the sole c'' subunit in the mammalian ring, adding a fifth helix and distinct topology compared with c/c'. The unique TM3-carboxyl position and proximity to a-subunit TM7 (from cross-linking) suggest c'' contributes specialized interfaces critical for torque transmission and proton exchange. Given the inferred one-per-ring stoichiometry, ATP6V0B is structurally nonredundant: damage to c'' would be expected to compromise the rotor’s integrity and the proton pathway for the entire complex (cipriano2008structureandregulation pages 2-4, forgac1999structureandproperties pages 3-3).
- Regulatory integration: E2F1-driven induction of ATP6V0B places this subunit under cell-cycle and growth control, aligning V-ATPase acidification capacity with anabolic signaling (mTORC1). This supports a model wherein proteolipid ring capacity (including ATP6V0B levels) is tuned to proliferative cues to modulate lysosomal signaling hubs (meoevoli2015vatpaseamaster pages 5-8).
- Evidence limitations and 2023–2024 gap: Direct 2023–2024 cryo-EM placement of c'' within human complexes and human genetics directly implicating ATP6V0B remain sparse in the accessible evidence compiled here. Nonetheless, long-standing biochemical and cross-linking evidence establish the topology, essential residue, and a–c'' proximities, and recent reviews reinforce the mammalian ring organization and accessory subunits near the ring (cipriano2008structureandregulation pages 2-4, yang2025vatpaseandlysosomal pages 6-7, chen2025theemergingroles pages 22-23).

Key sources with URLs and dates
- Forgac M. Structure and Properties of the Vacuolar (H+)-ATPases. J Biol Chem. 1999 May 14;274(19):12951–12954. https://doi.org/10.1074/jbc.274.19.12951 (mechanism; proteolipid subunits; essential carboxyl; early stoichiometry) (forgac1999structureandproperties pages 3-3).
- Cipriano DJ et al. Structure and regulation of the vacuolar ATPases. Biochim Biophys Acta. 2008 Jul–Aug;1777(7–8):599–604. https://doi.org/10.1016/j.bbabio.2008.03.013 (rotary mechanism; c/c'/c'' helices and essential residues; a–ring interactions; inhibitor binding site) (cipriano2008structureandregulation pages 2-4).
- Holliday LS. Vacuolar H+-ATPase: An Essential Multitasking Enzyme in Physiology and Pathophysiology. New J Sci. 2014;2014:675430. https://doi.org/10.1155/2014/675430 (subunit catalog including ATP6V0B as c''; physiological localizations) (holliday2014vacuolarh+atpasean pages 2-3).
- Chu A, Zirngibl RA, Manolson MF. The V-ATPase a3 Subunit. Int J Mol Sci. 2021 Jun;22(13):6934. https://doi.org/10.3390/ijms22136934 (membrane ring composition summarized as c9+c''; essential E98 in c'') (chu2021thevatpasea3 pages 2-3).
- Meo-Evoli N et al. V-ATPase: a master effector of E2F1-mediated lysosomal trafficking, mTORC1 activation and autophagy. Oncotarget. 2015 Aug;6(29):28057–28070. https://doi.org/10.18632/oncotarget.4812 (E2F1 directly induces ATP6V0B; coupling to mTORC1) (meoevoli2015vatpaseamaster pages 5-8).
- Groszer M. Rare human ATP6V1A variants provide unique insights into V-ATPase functions. Brain. 2022 Jul;145(8):2626–2628. https://doi.org/10.1093/brain/awac255 (context: subunit mutations cause neurological disease; lysosomal V-ATPase overview) (groszer2022rarehumanatp6v1a pages 7-9).
- Chen Y-Y et al. The Emerging Roles of V-ATPase-Dependent Lysosomal Acidification in Cardiovascular Disease. Biomolecules. 2025 Apr;15(4):525. https://doi.org/10.3390/biom15040525 (recent review summarizing assembly factors, localization, signaling links) (chen2025theemergingroles pages 22-23).
- Yang X, Holliday LS. V-ATPase and Lysosomal Energy Sensing in Periodontitis and MRONJ. Biomolecules. 2025 Jul;15(7):997. https://doi.org/10.3390/biom15070997 (mammalian ring organization including c''/ATP6V0B; accessory subunits within ring) (yang2025vatpaseandlysosomal pages 6-7).

Conclusions
Human ATP6V0B encodes the Vo proteolipid c'' subunit, a five-helix rotor component containing an essential buried carboxyl in TM3. It assembles with multiple c subunits to form the proteolipid c-ring that rotates against the a-subunit to translocate H+ during ATP-driven catalysis. ATP6V0B-containing V-ATPases acidify lysosomes, endosomes, Golgi, and secretory/synaptic vesicles and can localize to plasma membranes in specialized cells. Transcriptional upregulation by E2F1 links ATP6V0B to growth signaling, while accessory proteins embedded near the ring connect Vo composition to mTORC1 energy sensing. Although direct 2023–2024 ATP6V0B-specific structures and genetics remain limited in this evidence set, foundational biochemical and cross-linking work, supported by recent reviews, define ATP6V0B’s identity, essential residues, ring stoichiometry, and functional placement in mammalian V-ATPase biology (cipriano2008structureandregulation pages 2-4, holliday2014vacuolarh+atpasean pages 2-3, chu2021thevatpasea3 pages 2-3, forgac1999structureandproperties pages 3-3, yang2025vatpaseandlysosomal pages 6-7, meoevoli2015vatpaseamaster pages 5-8).

References

1. (holliday2014vacuolarh+atpasean pages 2-3): L. Shannon Holliday. Vacuolar h+-atpase: an essential multitasking enzyme in physiology and pathophysiology. New Journal of Science, 2014:1-21, Jan 2014. URL: https://doi.org/10.1155/2014/675430, doi:10.1155/2014/675430. This article has 59 citations.

2. (cipriano2008structureandregulation pages 2-4): Daniel J. Cipriano, Yanru Wang, Sarah Bond, Ayana Hinton, Kevin C. Jefferies, Jie Qi, and Michael Forgac. Structure and regulation of the vacuolar atpases. Biochimica et biophysica acta, 1777 7-8:599-604, Jul 2008. URL: https://doi.org/10.1016/j.bbabio.2008.03.013, doi:10.1016/j.bbabio.2008.03.013. This article has 226 citations.

3. (forgac1999structureandproperties pages 3-3): Michael Forgac. Structure and properties of the vacuolar (h+)-atpases*. The Journal of Biological Chemistry, 274:12951-12954, May 1999. URL: https://doi.org/10.1074/jbc.274.19.12951, doi:10.1074/jbc.274.19.12951. This article has 414 citations.

4. (chu2021thevatpasea3 pages 2-3): Anh Chu, Ralph A. Zirngibl, and Morris F. Manolson. The v-atpase a3 subunit: structure, function and therapeutic potential of an essential biomolecule in osteoclastic bone resorption. International Journal of Molecular Sciences, 22:6934, Jun 2021. URL: https://doi.org/10.3390/ijms22136934, doi:10.3390/ijms22136934. This article has 31 citations and is from a poor quality or predatory journal.

5. (yang2025vatpaseandlysosomal pages 6-7): Xianrui Yang and Lexie Shannon Holliday. V-atpase and lysosomal energy sensing in periodontitis and medicine-related osteonecrosis of the jaw. Biomolecules, 15:997, Jul 2025. URL: https://doi.org/10.3390/biom15070997, doi:10.3390/biom15070997. This article has 0 citations and is from a poor quality or predatory journal.

6. (chen2025theemergingroles pages 22-23): Yan-Yan Chen, Cai-Xia Liu, Hai-Xin Liu, and Shi-Yuan Wen. The emerging roles of vacuolar-type atpase-dependent lysosomal acidification in cardiovascular disease. Biomolecules, 15:525, Apr 2025. URL: https://doi.org/10.3390/biom15040525, doi:10.3390/biom15040525. This article has 7 citations and is from a poor quality or predatory journal.

7. (meoevoli2015vatpaseamaster pages 5-8): Nathalie Meo-Evoli, Eugènia Almacellas, Francesco Alessandro Massucci, Antonio Gentilella, Santiago Ambrosio, Sara C. Kozma, George Thomas, and Albert Tauler. V-atpase: a master effector of e2f1-mediated lysosomal trafficking, mtorc1 activation and autophagy. Oncotarget, 6:28057-28070, Aug 2015. URL: https://doi.org/10.18632/oncotarget.4812, doi:10.18632/oncotarget.4812. This article has 53 citations and is from a poor quality or predatory journal.

8. (groszer2022rarehumanatp6v1a pages 7-9): Matthias Groszer. Rare human atp6v1a variants provide unique insights into v-atpase functions. Brain : a journal of neurology, 145:2626-2628, Jul 2022. URL: https://doi.org/10.1093/brain/awac255, doi:10.1093/brain/awac255. This article has 5 citations.

Citations

1. cipriano2008structureandregulation pages 2-4
2. meoevoli2015vatpaseamaster pages 5-8
3. yang2025vatpaseandlysosomal pages 6-7
4. forgac1999structureandproperties pages 3-3
5. chen2025theemergingroles pages 22-23
6. https://doi.org/10.1074/jbc.274.19.12951
7. https://doi.org/10.1016/j.bbabio.2008.03.013
8. https://doi.org/10.1155/2014/675430
9. https://doi.org/10.3390/ijms22136934
10. https://doi.org/10.18632/oncotarget.4812
11. https://doi.org/10.1093/brain/awac255
12. https://doi.org/10.3390/biom15040525
13. https://doi.org/10.3390/biom15070997
14. https://doi.org/10.1155/2014/675430,
15. https://doi.org/10.1016/j.bbabio.2008.03.013,
16. https://doi.org/10.1074/jbc.274.19.12951,
17. https://doi.org/10.3390/ijms22136934,
18. https://doi.org/10.3390/biom15070997,
19. https://doi.org/10.3390/biom15040525,
20. https://doi.org/10.18632/oncotarget.4812,
21. https://doi.org/10.1093/brain/awac255,

Overview of ATP6V0B and the V-ATPase Complex

ATP6V0B (UniProt Q99437) encodes the V0 subunit b of the vacuolar H^+-ATPase (V-ATPase) in humans (genome.ucsc.edu). V-ATPase is a large multisubunit enzyme complex that uses the energy from ATP hydrolysis to pump protons (H^+) across membranes, thereby acidifying intracellular compartments (www.ncbi.nlm.nih.gov). The ATP6V0B gene product is a 21-kDa proteolipid membrane protein (also called subunit c'') that is a core component of the proton-conducting pore of V-ATPase (genome.ucsc.edu). This subunit is a multi-pass transmembrane protein found in the membrane of acidic organelles (analogous to the yeast vacuole/lysosome membrane) (genome.ucsc.edu). Consistent with its fundamental role, ATP6V0B is expressed ubiquitously in human tissues (genome.ucsc.edu) (with notable levels in metabolically active tissues like bone marrow and kidney (www.ncbi.nlm.nih.gov)), reflecting the widespread need for organelle acidification in cells.

Structure and Composition of the V-ATPase

V-ATPases are ATP-driven rotary proton pumps composed of two functional domains: an intrinsic membrane V0 domain that forms the proton channel, and a peripheral V1 domain that hydrolyzes ATP (academic.oup.com). ATP6V0B encodes one of the proteolipid subunits of the V0 domain. Within the V0 domain, multiple small proteolipid subunits assemble into a ring-shaped rotor (“c-ring”) embedded in the membrane (pmc.ncbi.nlm.nih.gov). In mammals, this ring consists of nine copies of the 16-kDa c-subunit (encoded by ATP6V0C) and one copy of the 21-kDa c''-subunit encoded by ATP6V0B (academic.oup.com). Together, these ten proteolipid subunits form the proton-conducting ring that rotates within the membrane. ATP6V0B corresponds to the sole c'' subunit in the ring (also known historically as ATP6F or yeast VMA16 homolog) (www.ncbi.nlm.nih.gov). Each proteolipid subunit spans the membrane multiple times (4 transmembrane helices per subunit is typical), and they collectively create a central pore for H^+ translocation (academic.oup.com). The V0 domain also includes a large a-subunit (ATP6V0A) that forms a proton channel interface with the c-ring, plus small accessory subunits (d, e, etc.) that help stabilize the complex (pmc.ncbi.nlm.nih.gov).

Mechanistically, V-ATPase operates by a rotational catalytic mechanism analogous to F-type ATP synthases (pmc.ncbi.nlm.nih.gov). The V1 sector (with subunits A, B, etc.) binds and hydrolyzes ATP, and this drives rotation of a central stalk connected to the c-ring rotor (pmc.ncbi.nlm.nih.gov). As the c-ring rotates against the stationary a-subunit, protons are transported from the cytosolic side to the luminal side of the membrane. A conserved acidic residue on each proteolipid subunit is essential for this proton transport: for example, a glutamate residue (Glu-139) in the c-subunit binds and releases protons during rotation (academic.oup.com). The a-subunit provides two half-channels and a critical basic residue (an arginine, Arg-735 in mammalian a-subunit) that cooperatively ensure protons pick up on the cytosolic side and drop off into the organelle lumen (academic.oup.com). In this way, ATP hydrolysis is tightly coupled to proton movement. The ATP hydrolysis reaction occurs on the V1 domain (subunits A/B) and can be summarized as:

ATP + H_2O → ADP + P_i (cytosol) + H^+ (cytosol) → H^+ (lumen),

meaning the free energy from ATP is used to pump H^+ across the membrane. Notably, structural studies (cryo-EM) of eukaryotic V-ATPases have visualized this rotary arrangement, confirming that the c-ring (with subunit ATP6V0B included) rotates within the membrane to carry protons to the channel in subunit a (academic.oup.com) (pmc.ncbi.nlm.nih.gov). The intact human V-ATPase has been resolved in several conformations, revealing how assembly of the V0 and V1 sectors enables this proton pumping action (academic.oup.com).

Because ATP6V0B is an integral part of the c-ring, it is critical for V-ATPase function. In fact, genetic ablation of proteolipid subunits in model organisms is lethal: for example, knockout of the mouse gene encoding the V0 proteolipid subunit resulted in early embryonic lethality (pmc.ncbi.nlm.nih.gov). This underscores that without ATP6V0B (or its paralogs), the proton channel cannot form properly, and cells cannot acidify their organelles – a fatal defect. ATP6V0B and related proteolipids are highly conserved across eukaryotes (academic.oup.com), highlighting their fundamental role in the rotary proton pump mechanism.

Biological Function and Cellular Processes

The primary function of ATP6V0B’s protein product is to enable ATP-dependent proton translocation into organelles, thereby acidifying the lumen of these compartments. This acidification is indispensable for a wide array of cellular processes. By creating a low pH environment inside vesicles and organelles, the V-ATPase (and ATP6V0B as part of it) supports several specific functions:

• Receptor-Mediated Endocytosis and Protein Sorting: Endosomes must be acidified for receptors to release their ligands and for proteins to be properly sorted to their next destination. V-ATPase-driven proton pumping causes the pH drop in early and late endosomes that is required for dissociation of receptor–ligand complexes and for targeting cargo to lysosomes or recycling pathways (www.ncbi.nlm.nih.gov). For example, LDL receptor, transferrin receptor, and many others depend on endosomal acidification to release bound cargo.
• Zymogen Activation: Secretory vesicles (e.g. in endocrine and exocrine cells) use V-ATPase to acidify their lumen, which triggers the conversion of pro-enzymes (zymogens) into active enzymes. A classic example is the activation of pro-hormones or digestive proenzymes (like pepsinogen to pepsin) upon exposure to acidic pH inside secretory granules (www.ncbi.nlm.nih.gov).
• Neurotransmitter Loading in Synaptic Vesicles: Neurons utilize V-ATPase to generate a proton electrochemical gradient in synaptic vesicles. This proton motive force drives neurotransmitter transporters that exchange lumenal H^+ for neurotransmitters, thereby loading neurotransmitters (e.g. glutamate, GABA) into synaptic vesicles. Without the V-ATPase establishing a proton gradient, synaptic vesicles could not uptake and store neurotransmitters (www.ncbi.nlm.nih.gov). Indeed, the synaptic vesicle proton gradient created by ATP6V0B-containing V-ATPases is essential for neurotransmission.
• Lysosomal Degradation and Autophagy: Lysosomes and autophagosomes require an acidic pH for optimal activity of acid hydrolases (proteases, lipases, nucleases). V-ATPase is responsible for acidifying these organelles, enabling efficient breakdown of macromolecules. This is crucial for the autophagy pathway and for general turnover of cellular components (academic.oup.com). Impaired acidification can lead to accumulation of undigested substrates and is linked to lysosomal storage disorders.
• Other pH-Dependent Processes: Virtually any cellular process that depends on pH gradients involves V-ATPase. This includes receptor recycling, antigen processing in endosomal/lysosomal compartments, virus entry via endosomes, and pH homeostasis in the Golgi and vacuolar system (which affects protein processing and trafficking) (academic.oup.com) (www.ncbi.nlm.nih.gov). For instance, the maturation of endocytic and secretory organelles is pH-dependent – cargo receptors cycle properly only if compartments are acidified in a timely manner.

In summary, ATP6V0B (as part of V-ATPase) is a housekeeping gene that underpins essential cellular functions by maintaining the acidic environment of intracellular organelles. Many of the specific pathways above illustrate how loss of V-ATPase activity has pleiotropic effects, but all of these effects stem from the single fundamental role: pumping protons. Indeed, the crucial role of V-ATPase is evident from the fact that disrupting proton pump function is catastrophic for cells – as noted, complete V-ATPase inhibition or subunit knockout causes loss of viability (pmc.ncbi.nlm.nih.gov). Even partial compromise can lead to disease (see below). Cells tightly regulate V-ATPase activity to balance these processes, turning assembly or activity up or down in response to cellular needs.

Subcellular Localization and Context of Activity

ATP6V0B’s protein product localizes to membranes of the endomembrane system, wherever V-ATPases are present. The prototypical location is the lysosomal membrane (and late endosome/vacuolar membranes), where V-ATPases pump protons into the lumen (academic.oup.com). Immunolocalization and cell fractionation studies confirm V-ATPase subunits are enriched in endo-lysosomal membranes, trans-Golgi network, and secretory vesicles in virtually all cell types (academic.oup.com). In these locations, ATP6V0B-containing V-ATPases acidify the organelle interior as described.

In addition to the intracellular organelles, certain specialized cells target V-ATPases to the plasma membrane to acidify the extracellular milieu for specific physiological functions. For example, osteoclasts (bone-resorbing cells) have a V-ATPase enriched in the membrane facing the bone surface; proton pumping by these V-ATPases creates an acidic microenvironment that dissolves bone mineral during resorption (pmc.ncbi.nlm.nih.gov). In the kidney, intercalated cells of the renal collecting duct express V-ATPases on their apical (urine-facing) membrane to secrete protons, which is critical for maintaining blood pH (this is the mechanism of urinary acidification) (pmc.ncbi.nlm.nih.gov). Other examples include the male reproductive tract (epididymal clear cells), which secrete protons via V-ATPase to create an acidic luminal pH essential for sperm maturation, and macrophages/osteoclasts using plasma-membrane V-ATPases for extracellular acidification in tissue remodeling (pmc.ncbi.nlm.nih.gov). These specialized localizations often involve tissue-specific isoforms of certain V-ATPase subunits (for instance, a kidney-specific B1 subunit in V1, or the osteoclast-specific a3 subunit in V0), but the ring subunits like ATP6V0B are shared across all V-ATPase complexes.

Inside the cell, V-ATPases (and thus ATP6V0B) continuously shuttle between compartments. For example, in many cells V-ATPases can cycle between the Golgi/endosomes and the plasma membrane via vesicular trafficking, depending on extracellular signals or the cell’s needs. Regulation of V-ATPase localization is one way cells control organelle pH. Notably, the IFITM proteins (interferon-induced transmembrane proteins) can alter V-ATPase distribution: IFITM3 has been shown to physically interact with ATP6V0B and other V0 subunits, which stabilizes V-ATPase complexes in endosomal membranes (pubmed.ncbi.nlm.nih.gov). This stabilization leads to changes in endosomal pH and endocytic trafficking. In the context of viral infection, IFITM3’s interaction with V-ATPase is thought to impede efficient endosomal acidification, thereby blocking viruses that require low pH for entry (pubmed.ncbi.nlm.nih.gov). This is an example of how localization and function of ATP6V0B-containing complexes can be modulated by cellular factors to achieve a specific outcome (antiviral defense in this case).

Pathways, Regulation, and Signaling Roles

Beyond its direct biochemical function as a proton pump, the V-ATPase (with ATP6V0B as an integral part) plays roles in cellular signaling and homeostasis. One of the most prominent examples is the pump’s involvement in the nutrient-sensing pathway that regulates mTORC1 (mechanistic Target of Rapamycin Complex 1). mTORC1 is a master regulator of cell growth that is activated on the surface of lysosomes in response to amino acids. Studies have shown that the lysosomal V-ATPase serves as a key upstream component of the mTORC1 activation pathway (pmc.ncbi.nlm.nih.gov). In the presence of amino acids, V-ATPase interacts with a scaffolding complex called Ragulator on the lysosomal membrane, in an amino-acid-dependent manner (pmc.ncbi.nlm.nih.gov). This interaction (which involves the V0 sector) is required to recruit and activate mTORC1. In essence, the V-ATPase acts like a sensor: its rotary activity or conformational state conveys the presence of nutrients inside lysosomes (“inside-out” sensing) to the Ragulator-Rag GTPase system (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Interestingly, while the proton-pumping activity of V-ATPase is necessary for proper amino acid balance in lysosomes, the signal to mTORC1 seems to depend on the physical assembly and rotation of the V-ATPase rather than just the pH itself (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). This represents a novel signaling role for a classical proton pump, linking lysosomal acidification status to cell growth signals (as first described in a 2011 Science article by Zoncu et al. (pmc.ncbi.nlm.nih.gov)). Additionally, under glucose starvation, V-ATPase detachment contributes to an alternate complex (with AXIN and AMPK) that downregulates mTORC1 and activates energy stress responses (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). These findings highlight that ATP6V0B, by virtue of being part of V-ATPase, is indirectly involved in critical signaling pathways like mTOR, which coordinate cell metabolism and growth in response to nutrient availability.

Other signaling and regulatory pathways involve V-ATPase activity as well. Wnt and Notch signaling, for example, require endosomal acidification for proper processing of signaling molecules or receptors (pmc.ncbi.nlm.nih.gov). Notch receptor activation depends on endosomal/lysosomal proteolysis (γ-secretase function) which in turn requires an acidic compartment. Impaired V-ATPase function can thus perturb Notch signaling, with implications in development and cancer. Similarly, pH dysregulation in endosomes can affect growth factor signaling (as many growth factor receptors are sorted and downregulated in a pH-dependent manner). Furthermore, the clearance of autophagosomes and subsequent signaling feedback (e.g. via TFEB, a transcription factor regulating lysosomal genes) needs proper lysosomal acidification – if lysosomes are not acidic, cells sense a dysfunction and may amplify lysosomal biogenesis signals. In neurons, changes in V-ATPase activity can influence synaptic vesicle cycling and neurotransmitter signaling (with potential downstream effects on neural circuitry). These examples underscore that while ATP6V0B is not a “signaling protein” in the traditional sense (it has no enzymatic signaling domain), the activity of the V-ATPase complex is deeply intertwined with cellular signaling networks that respond to internal and external stimuli.

Regulation of V-ATPase itself often occurs via reversible assembly of the V1 and V0 domains. In response to cellular conditions (like glucose levels, pH, and hormonal signals), cells can regulate how many V-ATPase complexes are fully assembled and active on a given membrane. When V1 dissociates from V0, the enzyme is inactive (this is a way to temporarily shut off proton pumping to save energy). Under favorable conditions, V1 re-attaches to V0 to resume pumping. This process has been best described in yeast but also occurs in mammalian cells. ATP6V0B, being part of V0, is always present in the membrane but might sit in an inactive V0 sector until the V1 sector attaches. There are also dedicated assembly factors (e.g. VMA21, VMA12, VMA22 in the ER for V0 assembly in yeast) that ensure proteolipid subunits like ATP6V0B insert properly into the membrane and form the ring (pubmed.ncbi.nlm.nih.gov). Mutations in these assembly factors can phenocopy V0 subunit loss. Thus, the cell has multiple layers of control – both in assembling the complex during biosynthesis and in dynamically modulating assembly during cellular responses.

Clinical Significance and Current Research

Defects in V-ATPase function have been implicated in various diseases, although ATP6V0B-specific mutations in humans have not yet been well-characterized in the literature (likely because complete loss-of-function would be lethal and partial loss may be rare). However, the essential nature of ATP6V0B is evident by analogy to other subunits. For instance, heterozygous missense mutations in ATP6V0C (the partner c-subunit in the proton c-ring) were recently found to cause a neurodevelopmental disorder with epilepsy (academic.oup.com). Patients with ATP6V0C mutations showed developmental delay, seizures, and brain abnormalities, which highlights how sensitive neuronal function is to perturbations in organelle acidification. The ATP6V0C mutants were shown to impair V-ATPase proton translocation (e.g. by affecting the critical Glu-139 residue), thereby compromising lysosomal acidification (academic.oup.com). By extension, a damaging mutation in ATP6V0B would be expected to similarly disrupt the c-ring and impair proton pump activity, potentially leading to severe cellular and tissue dysfunction. Indeed, some cases of inborn errors of metabolism or neurodevelopment may eventually be traced to ATP6V0B when genome sequencing identifies variants, although as of 2023 no such disorder is definitively linked to ATP6V0B. It’s worth noting that large deletions encompassing ATP6V0B (chromosome 1p34.1) could contribute to complex syndromes, but more research is needed.

On the other hand, organ-specific isoforms of other V-ATPase subunits are known disease genes. For example, mutations in the kidney-specific V1 B1 subunit (gene ATP6V1B1) or the V0 a4 subunit (ATP6V0A4) cause distal renal tubular acidosis – a disorder where the kidney cannot acidify urine, leading to systemic metabolic acidosis (pubmed.ncbi.nlm.nih.gov). Similarly, mutations in the osteoclast-specific V0 a3 subunit (TCIRG1 gene) cause osteopetrosis, a bone disease due to failure of osteoclasts to resorb bone (since they cannot acidify the resorption lacuna). These disease connections underscore the critical roles of V-ATPase in specific physiological settings. While ATP6V0B is common to all tissues, it is part of the same machinery, so understanding its function is relevant to these pathologies as well.

Therapeutic and real-world implications: The V-ATPase has drawn interest as a drug target for cancer and other diseases. Tumor cells often rely on V-ATPases to acidify their environment and survive in hypoxic, nutrient-poor conditions. Inhibiting V-ATPase can induce cytotoxicity in cancer cells, reduce metastasis (by lowering the ability to acidify the extracellular matrix), and modulate drug resistance (by affecting pH-dependent drug sequestration in organelles) (pmc.ncbi.nlm.nih.gov). However, since V-ATPase is essential in normal cells too, global V-ATPase inhibitors like bafilomycin and concanamycin (potent research tools that bind the proteolipid subunits) are highly toxic and not clinically viable (pmc.ncbi.nlm.nih.gov). Current research is looking at more selective approaches – for example, targeting specific V-ATPase isoforms that are enriched in certain tissues or tumors, or modulating regulators of V-ATPase assembly. One 2022 study suggested that certain proton pump inhibitors (used for stomach acid) might incidentally promote V-ATPase assembly in endosomes, enhancing uptake of extracellular vesicles (pmc.ncbi.nlm.nih.gov), hinting at off-target effects on V-ATPase function. Additionally, there is interest in antiviral strategies: since some viruses (e.g. influenza, SARS-CoV-2) require endosomal acidification to enter cells, transiently inhibiting V-ATPase in host cells could block infection. Indeed, IFITM3’s mechanism for broad antiviral action, as noted, involves interaction with ATP6V0B and V-ATPase to alter endosomal pH (pubmed.ncbi.nlm.nih.gov).

From a biochemical standpoint, ATP6V0B itself could be a target for modulation if small molecules were found to specifically disrupt the assembly of the c-ring. Recent high-resolution structures of V-ATPase may facilitate such drug design by revealing pockets at subunit interfaces (academic.oup.com). For example, if a compound could lock the c-ring or prevent ATP6V0B from incorporating correctly, it might selectively kill cancer cells with high V-ATPase dependence. Conversely, in conditions of lysosomal dysfunction, strategies to boost V-ATPase activity (and thereby acidification) could be beneficial. This is an area of ongoing research, as scientists explore V-ATPase modulators for diseases like osteoporosis, cancer, and neurodegeneration (pmc.ncbi.nlm.nih.gov).

Finally, it’s important to note that ATP6V0B and the V0 sector have been implicated in functions beyond proton pumping. Some evidence suggests that V0 subunits might form channels or have membrane fusion roles in certain contexts (independent of V1). For instance, studies in yeast have hinted that the V0 domain might participate in vacuole membrane fusion during homotypic fusion events, though the exact relevance in mammals remains debated (pmc.ncbi.nlm.nih.gov). If true, ATP6V0B could be part of a membrane fusion machinery. However, the prevailing consensus is that the well-established role of ATP6V0B is as a proton-conducting subunit of the V-ATPase, and through this role it influences numerous cellular processes and pathways.

In summary, ATP6V0B is a vital gene encoding a structural subunit of the vacuolar H^+-ATPase proton pump. Its protein product forms part of the rotary proton channel that acidifies intracellular organelles, enabling key processes like endocytosis, protein degradation, and neurotransmitter storage. It localizes to organelle membranes (and certain plasma membranes in specialized cells) where it carries out proton transport. By doing so it also intersects with signaling pathways (e.g. mTORC1 nutrient sensing) and can be a factor in disease mechanisms. Ongoing research (as of 2023-2024) continues to uncover details of V-ATPase regulation, structure, and potential for targeted therapy, underlining the continued importance of ATP6V0B in cell biology and medicine (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).

Citations

1. AnnotationURLCitation(end_index=334, start_index=152, title='Human Gene ATP6V0B (ENST00000472174.7) from GENCODE V48', type='url_citation', url='https://genome.ucsc.edu/cgi-bin/hgGene?db=hg38&hgg_gene=ENST00000472174.7&hgg_type=knownGene#:~:text=FUNCTION%3A%20Proton,ATPase%20proteolipid%20subunit%20family')
2. AnnotationURLCitation(end_index=664, start_index=515, title='ATP6V0B ATPase H+ transporting V0 subunit b [Homo sapiens (human)] - Gene - NCBI', type='url_citation', url='https://www.ncbi.nlm.nih.gov/gene?Cmd=DetailsSearch&Db=gene&Term=533#:~:text=Summary%20This%20gene%20encodes%20a,Expression')
3. AnnotationURLCitation(end_index=1013, start_index=831, title='Human Gene ATP6V0B (ENST00000472174.7) from GENCODE V48', type='url_citation', url='https://genome.ucsc.edu/cgi-bin/hgGene?db=hg38&hgg_gene=ENST00000472174.7&hgg_type=knownGene#:~:text=FUNCTION%3A%20Proton,ATPase%20proteolipid%20subunit%20family')
4. AnnotationURLCitation(end_index=1342, start_index=1160, title='Human Gene ATP6V0B (ENST00000472174.7) from GENCODE V48', type='url_citation', url='https://genome.ucsc.edu/cgi-bin/hgGene?db=hg38&hgg_gene=ENST00000472174.7&hgg_type=knownGene#:~:text=FUNCTION%3A%20Proton,ATPase%20proteolipid%20subunit%20family')
5. AnnotationURLCitation(end_index=1653, start_index=1437, title='Human Gene ATP6V0B (ENST00000472174.7) from GENCODE V48', type='url_citation', url='https://genome.ucsc.edu/cgi-bin/hgGene?db=hg38&hgg_gene=ENST00000472174.7&hgg_type=knownGene#:~:text=intracellular%20compartments%20in%20eukaryotic%20cells,ATPase%20proteolipid%20subunit%20family')
6. AnnotationURLCitation(end_index=1920, start_index=1735, title='ATP6V0B ATPase H+ transporting V0 subunit b [Homo sapiens (human)] - Gene - NCBI', type='url_citation', url='https://www.ncbi.nlm.nih.gov/gene?Cmd=DetailsSearch&Db=gene&Term=533#:~:text=Expression%20Ubiquitous%20expression%20in%20bone,25%20other%20tissues%20See%20more')
7. AnnotationURLCitation(end_index=2385, start_index=2237, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=acidify%20organelles.%20The%20V,ATPase%20plays%20a%20crucial')
8. AnnotationURLCitation(end_index=2709, start_index=2585, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=V,ring.%20Created%20with%20BioRender.com')
9. AnnotationURLCitation(end_index=3032, start_index=2872, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=match%20at%20L1412%20Nine%20copies,mRNA%2C%20which%20would%20result%20in')
10. AnnotationURLCitation(end_index=3456, start_index=3265, title='ATP6V0B ATPase H+ transporting V0 subunit b [Homo sapiens (human)] - Gene - NCBI', type='url_citation', url='https://www.ncbi.nlm.nih.gov/gene?Cmd=DetailsSearch&Db=gene&Term=533#:~:text=Also%20known%20as%20ATP6F%3B%20HATPL%3B,Alternative%20splicing%20results%20in%20multiple')
11. AnnotationURLCitation(end_index=3745, start_index=3633, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=ATP6V0C%2C%20a%20three,1')
12. AnnotationURLCitation(end_index=4059, start_index=3935, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=V,ring.%20Created%20with%20BioRender.com')
13. AnnotationURLCitation(end_index=4299, start_index=4175, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=V,ring.%20Created%20with%20BioRender.com')
14. AnnotationURLCitation(end_index=4566, start_index=4442, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=V,ring.%20Created%20with%20BioRender.com')
15. AnnotationURLCitation(end_index=5023, start_index=4911, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=ATP6V0C%2C%20a%20three,1')
16. AnnotationURLCitation(end_index=5359, start_index=5247, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=ATP6V0C%2C%20a%20three,1')
17. AnnotationURLCitation(end_index=6051, start_index=5915, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=the%20c,and%20interact%20with%20ATP6V0A%20during')
18. AnnotationURLCitation(end_index=6216, start_index=6052, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=is%20hydrolyzed%20at%20the%20intersection,ring.%20Created%20with%20BioRender.com')
19. AnnotationURLCitation(end_index=6508, start_index=6371, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=missense%20variants%2C%20we%20first%20turned,ring')
20. AnnotationURLCitation(end_index=6963, start_index=6803, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=necessary%20for%20many%20essential%20cell,mouse%20lines%20have%20been%20made')
21. AnnotationURLCitation(end_index=7307, start_index=7195, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=ATP6V0C%2C%20a%20three,1')
22. AnnotationURLCitation(end_index=8363, start_index=8214, title='ATP6V0B ATPase H+ transporting V0 subunit b [Homo sapiens (human)] - Gene - NCBI', type='url_citation', url='https://www.ncbi.nlm.nih.gov/gene?Cmd=DetailsSearch&Db=gene&Term=533#:~:text=This%20gene%20encodes%20a%20portion,Expression')
23. AnnotationURLCitation(end_index=9036, start_index=8849, title='ATP6V0B ATPase H+ transporting V0 subunit b [Homo sapiens (human)] - Gene - NCBI', type='url_citation', url='https://www.ncbi.nlm.nih.gov/gene?Cmd=DetailsSearch&Db=gene&Term=533#:~:text=This%20gene%20encodes%20a%20portion,Alternative%20splicing%20results%20in%20multiple')
24. AnnotationURLCitation(end_index=9693, start_index=9498, title='ATP6V0B ATPase H+ transporting V0 subunit b [Homo sapiens (human)] - Gene - NCBI', type='url_citation', url='https://www.ncbi.nlm.nih.gov/gene?Cmd=DetailsSearch&Db=gene&Term=533#:~:text=a%20multisubunit%20enzyme%20that%20mediates,Alternative%20splicing%20results%20in%20multiple')
25. AnnotationURLCitation(end_index=10279, start_index=10187, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=V,71')
26. AnnotationURLCitation(end_index=10835, start_index=10743, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=V,71')
27. AnnotationURLCitation(end_index=10985, start_index=10836, title='ATP6V0B ATPase H+ transporting V0 subunit b [Homo sapiens (human)] - Gene - NCBI', type='url_citation', url='https://www.ncbi.nlm.nih.gov/gene?Cmd=DetailsSearch&Db=gene&Term=533#:~:text=This%20gene%20encodes%20a%20portion,Expression')
28. AnnotationURLCitation(end_index=11899, start_index=11739, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=necessary%20for%20many%20essential%20cell,mouse%20lines%20have%20been%20made')
29. AnnotationURLCitation(end_index=12496, start_index=12404, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=V,71')
30. AnnotationURLCitation(end_index=12780, start_index=12688, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=V,71')
31. AnnotationURLCitation(end_index=13461, start_index=13298, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=In%20addition%20to%20its%20participation,as%20a%20transmembrane%20proton%20pump')
32. AnnotationURLCitation(end_index=13865, start_index=13702, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=In%20addition%20to%20its%20participation,as%20a%20transmembrane%20proton%20pump')
33. AnnotationURLCitation(end_index=14326, start_index=14163, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=In%20addition%20to%20its%20participation,as%20a%20transmembrane%20proton%20pump')
34. AnnotationURLCitation(end_index=15345, start_index=15207, title='Interferon-inducible transmembrane proteins of the innate immune response act as membrane organizers by influencing clathrin and v-ATPase localization and function - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/22467717/#:~:text=Co,appropriate%20subcellular%20localization%20of%20clathrin')
35. AnnotationURLCitation(end_index=15745, start_index=15607, title='Interferon-inducible transmembrane proteins of the innate immune response act as membrane organizers by influencing clathrin and v-ATPase localization and function - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/22467717/#:~:text=Co,appropriate%20subcellular%20localization%20of%20clathrin')
36. AnnotationURLCitation(end_index=16684, start_index=16539, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=match%20at%20L887%20the%20V,that%20is%20necessary%20for%20the')
37. AnnotationURLCitation(end_index=16991, start_index=16846, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=match%20at%20L887%20the%20V,that%20is%20necessary%20for%20the')
38. AnnotationURLCitation(end_index=17408, start_index=17283, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=the%20V,that%20is%20necessary%20for%20the')
39. AnnotationURLCitation(end_index=17584, start_index=17409, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=During%20mTORC1%20activation%2C%20under%20conditions,recruit%20mTORC1%20to%20the%20lysosome')
40. AnnotationURLCitation(end_index=17982, start_index=17830, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=acids.%20Specifically%2C%20the%20V,that%20is%20necessary%20for%20the')
41. AnnotationURLCitation(end_index=18129, start_index=17983, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=recruits%20mTORC1%20to%20the%20lysosomal,ATPase%20appears%20to')
42. AnnotationURLCitation(end_index=18464, start_index=18331, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=%2A%20116.Zoncu%20R%2C%20Bar,PMC%20free%20article')
43. AnnotationURLCitation(end_index=18776, start_index=18648, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=match%20at%20L891%20translocation%20and,Axin')
44. AnnotationURLCitation(end_index=18911, start_index=18777, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=disassociation%20from%20the%20lysosome%20and,After')
45. AnnotationURLCitation(end_index=19520, start_index=19344, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=sensing%20along%20the%20mammalian%20target,numerous%20and%20varied%20pathologies%20including')
46. AnnotationURLCitation(end_index=21675, start_index=21563, title='Structural basis of V-ATPase VO region assembly by Vma12p, 21p, and 22p - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/36724250/#:~:text=PubMed%20pubmed,subunit%20enzymes')
47. AnnotationURLCitation(end_index=22596, start_index=22484, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=ATP6V0C%2C%20a%20three,1')
48. AnnotationURLCitation(end_index=23078, start_index=22956, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=c%E2%80%B2%E2%80%B2%20subunit%20,1')
49. AnnotationURLCitation(end_index=24152, start_index=23986, title='Mutations in ATP6V1B1 and ATP6V0A4 genes cause recessive distal renal tubular acidosis in Mexican families - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/27247958/#:~:text=Mutations%20in%20ATP6V1B1%20and%20ATP6V0A4,metabolic%20acidosis%20with%20normal%20anion')
50. AnnotationURLCitation(end_index=25226, start_index=25089, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=and%20used%20in%20physiological%20studies,see%20below')
51. AnnotationURLCitation(end_index=25594, start_index=25457, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=and%20used%20in%20physiological%20studies,see%20below')
52. AnnotationURLCitation(end_index=26149, start_index=25991, title='Proton pump inhibitors enhance macropinocytosis‐mediated extracellular vesicle endocytosis by inducing membrane v‐ATPase assembly - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC10966248/#:~:text=Proton%20pump%20inhibitors%20enhance%20macropinocytosis%E2%80%90mediated,')
53. AnnotationURLCitation(end_index=26701, start_index=26563, title='Interferon-inducible transmembrane proteins of the innate immune response act as membrane organizers by influencing clathrin and v-ATPase localization and function - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/22467717/#:~:text=Co,appropriate%20subcellular%20localization%20of%20clathrin')
54. AnnotationURLCitation(end_index=27123, start_index=26986, title='ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy | Brain | Oxford Academic', type='url_citation', url='https://academic.oup.com/brain/article/146/4/1357/6694191#:~:text=missense%20variants%2C%20we%20first%20turned,ring')
55. AnnotationURLCitation(end_index=27714, start_index=27577, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=and%20used%20in%20physiological%20studies,see%20below')
56. AnnotationURLCitation(end_index=28296, start_index=28161, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=proteolipid%20ring%20acts%20as%20a,Google%20Scholar')
57. AnnotationURLCitation(end_index=29482, start_index=29345, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=and%20used%20in%20physiological%20studies,see%20below')
58. AnnotationURLCitation(end_index=29628, start_index=29483, title='The H+-ATPase (V-ATPase): from proton pump to signaling complex in health and disease - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC8294626/#:~:text=match%20at%20L887%20the%20V,that%20is%20necessary%20for%20the')