1
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Khan MM, Wilkens S. Molecular mechanism of Oxr1p mediated disassembly of yeast V-ATPase. EMBO Rep 2024; 25:2323-2347. [PMID: 38565737 PMCID: PMC11094088 DOI: 10.1038/s44319-024-00126-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 03/07/2024] [Accepted: 03/09/2024] [Indexed: 04/04/2024] Open
Abstract
The eukaryotic vacuolar H+-ATPase (V-ATPase) is regulated by reversible disassembly into autoinhibited V1-ATPase and Vo proton channel subcomplexes. We recently reported that the TLDc protein Oxr1p induces V-ATPase disassembly in vitro. Whether and how Oxr1p is involved in enzyme disassembly in vivo, however, is not known. Here, using yeast genetics and fluorescence microscopy, we show that Oxr1p is essential for efficient V-ATPase disassembly in the cell. Supporting biochemical and biophysical in vitro experiments show that whereas Oxr1p-driven holoenzyme disassembly can occur in the absence of nucleotides, the presence of ATP greatly accelerates the process. ATP hydrolysis is needed, however, for subsequent release of Oxr1p so that the free V1 can adopt the autoinhibited conformation. Overall, our study unravels the molecular mechanism of Oxr1p-induced disassembly that occurs in vivo as part of the canonical V-ATPase regulation by reversible disassembly.
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Affiliation(s)
- Md Murad Khan
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA.
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2
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Indrawinata K, Argiropoulos P, Sugita S. Structural and functional understanding of disease-associated mutations in V-ATPase subunit a1 and other isoforms. Front Mol Neurosci 2023; 16:1135015. [PMID: 37465367 PMCID: PMC10352029 DOI: 10.3389/fnmol.2023.1135015] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 06/09/2023] [Indexed: 07/20/2023] Open
Abstract
The vacuolar-type ATPase (V-ATPase) is a multisubunit protein composed of the cytosolic adenosine triphosphate (ATP) hydrolysis catalyzing V1 complex, and the integral membrane complex, Vo, responsible for proton translocation. The largest subunit of the Vo complex, subunit a, enables proton translocation upon ATP hydrolysis, mediated by the cytosolic V1 complex. Four known subunit a isoforms (a1-a4) are expressed in different cellular locations. Subunit a1 (also known as Voa1), the neural isoform, is strongly expressed in neurons and is encoded by the ATP6V0A1 gene. Global knockout of this gene in mice causes embryonic lethality, whereas pyramidal neuron-specific knockout resulted in neuronal cell death with impaired spatial and learning memory. Recently reported, de novo and biallelic mutations of the human ATP6V0A1 impair autophagic and lysosomal activities, contributing to neuronal cell death in developmental and epileptic encephalopathies (DEE) and early onset progressive myoclonus epilepsy (PME). The de novo heterozygous R740Q mutation is the most recurrent variant reported in cases of DEE. Homology studies suggest R740 deprotonates protons from specific glutamic acid residues in subunit c, highlighting its importance to the overall V-ATPase function. In this paper, we discuss the structure and mechanism of the V-ATPase, emphasizing how mutations in subunit a1 can lead to lysosomal and autophagic dysfunction in neurodevelopmental disorders, and how mutations to the non-neural isoforms, a2-a4, can also lead to various genetic diseases. Given the growing discovery of disease-causing variants of V-ATPase subunit a and its function as a pump-based regulator of intracellular organelle pH, this multiprotein complex warrants further investigation.
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Affiliation(s)
- Karen Indrawinata
- Division of Translational and Experimental Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, Canada
| | - Peter Argiropoulos
- Division of Translational and Experimental Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, Canada
| | - Shuzo Sugita
- Division of Translational and Experimental Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, Canada
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
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3
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Endosomal v-ATPase as a Sensor Determining Myocardial Substrate Preference. Metabolites 2022; 12:metabo12070579. [PMID: 35888703 PMCID: PMC9316095 DOI: 10.3390/metabo12070579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/16/2022] [Accepted: 06/20/2022] [Indexed: 11/17/2022] Open
Abstract
The heart is a metabolically flexible omnivore that can utilize a variety of substrates for energy provision. To fulfill cardiac energy requirements, the healthy adult heart mainly uses long-chain fatty acids and glucose in a balanced manner, but when exposed to physiological or pathological stimuli, it can switch its substrate preference to alternative substrates such as amino acids (AAs) and ketone bodies. Using the failing heart as an example, upon stress, the fatty acid/glucose substrate balance is upset, resulting in an over-reliance on either fatty acids or glucose. A chronic fuel shift towards a single type of substrate is linked with cardiac dysfunction. Re-balancing myocardial substrate preference is suggested as an effective strategy to rescue the failing heart. In the last decade, we revealed that vacuolar-type H+-ATPase (v-ATPase) functions as a key regulator of myocardial substrate preference and, therefore, as a novel potential treatment approach for the failing heart. Fatty acids, glucose, and AAs selectively influence the assembly state of v-ATPase resulting in modulation of its proton-pumping activity. In this review, we summarize these novel insights on v-ATPase as an integrator of nutritional information. We also describe its exploitation as a therapeutic target with focus on supplementation of AA as a nutraceutical approach to fight lipid-induced insulin resistance and contractile dysfunction of the heart.
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4
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Vasanthakumar T, Keon KA, Bueler SA, Jaskolka MC, Rubinstein JL. Coordinated conformational changes in the V 1 complex during V-ATPase reversible dissociation. Nat Struct Mol Biol 2022; 29:430-439. [PMID: 35469063 DOI: 10.1038/s41594-022-00757-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 03/03/2022] [Indexed: 11/10/2022]
Abstract
Vacuolar-type ATPases (V-ATPases) are rotary enzymes that acidify intracellular compartments in eukaryotic cells. These multi-subunit complexes consist of a cytoplasmic V1 region that hydrolyzes ATP and a membrane-embedded VO region that transports protons. V-ATPase activity is regulated by reversible dissociation of the two regions, with the isolated V1 and VO complexes becoming autoinhibited on disassembly and subunit C subsequently detaching from V1. In yeast, assembly of the V1 and VO regions is mediated by the regulator of the ATPase of vacuoles and endosomes (RAVE) complex through an unknown mechanism. We used cryogenic-electron microscopy of yeast V-ATPase to determine structures of the intact enzyme, the dissociated but complete V1 complex and the V1 complex lacking subunit C. On separation, V1 undergoes a dramatic conformational rearrangement, with its rotational state becoming incompatible for reassembly with VO. Loss of subunit C allows V1 to match the rotational state of VO, suggesting how RAVE could reassemble V1 and VO by recruiting subunit C.
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Affiliation(s)
- Thamiya Vasanthakumar
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Biochemistry, The University of Toronto, Toronto, Ontario, Canada
| | - Kristine A Keon
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Medical Biophysics, The University of Toronto, Toronto, Ontario, Canada
| | - Stephanie A Bueler
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Michael C Jaskolka
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - John L Rubinstein
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, Ontario, Canada. .,Department of Biochemistry, The University of Toronto, Toronto, Ontario, Canada. .,Department of Medical Biophysics, The University of Toronto, Toronto, Ontario, Canada.
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5
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Jaskolka MC, Tarsio M, Smardon AM, Khan MM, Kane PM. Defining steps in RAVE-catalyzed V-ATPase assembly using purified RAVE and V-ATPase subcomplexes. J Biol Chem 2021; 296:100703. [PMID: 33895134 PMCID: PMC8138766 DOI: 10.1016/j.jbc.2021.100703] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 04/20/2021] [Accepted: 04/21/2021] [Indexed: 12/30/2022] Open
Abstract
The vacuolar H+-ATPase (V-ATPase) is a highly conserved proton pump responsible for the acidification of intracellular organelles in virtually all eukaryotic cells. V-ATPases are regulated by the rapid and reversible disassembly of the peripheral V1 domain from the integral membrane Vo domain, accompanied by release of the V1 C subunit from both domains. Efficient reassembly of V-ATPases requires the Regulator of the H+-ATPase of Vacuoles and Endosomes (RAVE) complex in yeast. Although a number of pairwise interactions between RAVE and V-ATPase subunits have been mapped, the low endogenous levels of the RAVE complex and lethality of constitutive RAV1 overexpression have hindered biochemical characterization of the intact RAVE complex. We describe a novel inducible overexpression system that allows purification of native RAVE and RAVE–V1 complexes. Both purified RAVE and RAVE–V1 contain substoichiometric levels of subunit C. RAVE–V1 binds tightly to expressed subunit C in vitro, but binding of subunit C to RAVE alone is weak. Neither RAVE nor RAVE–V1 interacts with the N-terminal domain of Vo subunit Vph1 in vitro. RAVE–V1 complexes, like isolated V1, have no MgATPase activity, suggesting that RAVE cannot reverse V1 inhibition generated by rotation of subunit H and entrapment of MgADP that occur upon disassembly. However, purified RAVE can accelerate reassembly of V1 carrying a mutant subunit H incapable of inhibition with Vo complexes reconstituted into lipid nanodiscs, consistent with its catalytic activity in vivo. These results provide new insights into the possible order of events in V-ATPase reassembly and the roles of the RAVE complex in each event.
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Affiliation(s)
- Michael C Jaskolka
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Maureen Tarsio
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Anne M Smardon
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Md Murad Khan
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.
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6
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Wang L, Wu D, Robinson CV, Wu H, Fu TM. Structures of a Complete Human V-ATPase Reveal Mechanisms of Its Assembly. Mol Cell 2020; 80:501-511.e3. [PMID: 33065002 PMCID: PMC7655608 DOI: 10.1016/j.molcel.2020.09.029] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 08/21/2020] [Accepted: 08/25/2020] [Indexed: 12/22/2022]
Abstract
Vesicular- or vacuolar-type adenosine triphosphatases (V-ATPases) are ATP-driven proton pumps comprised of a cytoplasmic V1 complex for ATP hydrolysis and a membrane-embedded Vo complex for proton transfer. They play important roles in acidification of intracellular vesicles, organelles, and the extracellular milieu in eukaryotes. Here, we report cryoelectron microscopy structures of human V-ATPase in three rotational states at up to 2.9-Å resolution. Aided by mass spectrometry, we build all known protein subunits with associated N-linked glycans and identify glycolipids and phospholipids in the Vo complex. We define ATP6AP1 as a structural hub for Vo complex assembly because it connects to multiple Vo subunits and phospholipids in the c-ring. The glycolipids and the glycosylated Vo subunits form a luminal glycan coat critical for V-ATPase folding, localization, and stability. This study identifies mechanisms of V-ATPase assembly and biogenesis that rely on the integrated roles of ATP6AP1, glycans, and lipids.
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Affiliation(s)
- Longfei Wang
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA.
| | - Di Wu
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, UK
| | - Carol V Robinson
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, UK
| | - Hao Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA.
| | - Tian-Min Fu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA; Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210, USA; The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA.
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7
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Banerjee S, Kane PM. Regulation of V-ATPase Activity and Organelle pH by Phosphatidylinositol Phosphate Lipids. Front Cell Dev Biol 2020; 8:510. [PMID: 32656214 PMCID: PMC7324685 DOI: 10.3389/fcell.2020.00510] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 05/28/2020] [Indexed: 12/14/2022] Open
Abstract
Luminal pH and the distinctive distribution of phosphatidylinositol phosphate (PIP) lipids are central identifying features of organelles in all eukaryotic cells that are also critical for organelle function. V-ATPases are conserved proton pumps that populate and acidify multiple organelles of the secretory and the endocytic pathway. Complete loss of V-ATPase activity causes embryonic lethality in higher animals and conditional lethality in yeast, while partial loss of V-ATPase function is associated with multiple disease states. On the other hand, many cancer cells increase their virulence by upregulating V-ATPase expression and activity. The pH of individual organelles is tightly controlled and essential for function, but the mechanisms for compartment-specific pH regulation are not completely understood. There is substantial evidence indicating that the PIP content of membranes influences organelle pH. We present recent evidence that PIPs interact directly with subunit isoforms of the V-ATPase to dictate localization of V-ATPase subpopulations and participate in their regulation. In yeast cells, which have only one set of organelle-specific V-ATPase subunit isoforms, the Golgi-enriched lipid PI(4)P binds to the cytosolic domain of the Golgi-enriched a-subunit isoform Stv1, and loss of PI(4)P binding results in mislocalization of Stv1-containing V-ATPases from the Golgi to the vacuole/lysosome. In contrast, levels of the vacuole/lysosome-enriched signaling lipid PI(3,5)P2 affect assembly and activity of V-ATPases containing the Vph1 a-subunit isoform. Mutations in the Vph1 isoform that disrupt the lipid interaction increase sensitivity to stress. These studies have decoded “zip codes” for PIP lipids in the cytosolic N-terminal domain of the a-subunit isoforms of the yeast V-ATPase, and similar interactions between PIP lipids and the V-ATPase subunit isoforms are emerging in higher eukaryotes. In addition to direct effects on the V-ATPase, PIP lipids are also likely to affect organelle pH indirectly, through interactions with other membrane transporters. We discuss direct and indirect effects of PIP lipids on organelle pH, and the functional consequences of the interplay between PIP lipid content and organelle pH.
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Affiliation(s)
- Subhrajit Banerjee
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, United States
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
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8
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Collins MP, Forgac M. Regulation and function of V-ATPases in physiology and disease. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183341. [PMID: 32422136 DOI: 10.1016/j.bbamem.2020.183341] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 04/30/2020] [Accepted: 05/03/2020] [Indexed: 02/07/2023]
Abstract
The vacuolar H+-ATPases (V-ATPases) are essential, ATP-dependent proton pumps present in a variety of eukaryotic cellular membranes. Intracellularly, V-ATPase-dependent acidification functions in such processes as membrane traffic, protein degradation, autophagy and the coupled transport of small molecules. V-ATPases at the plasma membrane of certain specialized cells function in such processes as bone resorption, sperm maturation and urinary acidification. V-ATPases also function in disease processes such as pathogen entry and cancer cell invasiveness, while defects in V-ATPase genes are associated with disorders such as osteopetrosis, renal tubular acidosis and neurodegenerative diseases. This review highlights recent advances in our understanding of V-ATPase structure, mechanism, function and regulation, with an emphasis on the signaling pathways controlling V-ATPase assembly in mammalian cells. The role of V-ATPases in cancer and other human pathologies, and the prospects for therapeutic intervention, are also discussed.
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Affiliation(s)
- Michael P Collins
- Cell, Molecular and Developmental Biology, Tufts University Graduate School of Biomedical Sciences, United States of America
| | - Michael Forgac
- Cell, Molecular and Developmental Biology, Tufts University Graduate School of Biomedical Sciences, United States of America; Dept. of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, United States of America.
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9
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Vasanthakumar T, Rubinstein JL. Structure and Roles of V-type ATPases. Trends Biochem Sci 2020; 45:295-307. [PMID: 32001091 DOI: 10.1016/j.tibs.2019.12.007] [Citation(s) in RCA: 90] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 12/05/2019] [Accepted: 12/31/2019] [Indexed: 12/19/2022]
Abstract
V-ATPases are membrane-embedded protein complexes that function as ATP hydrolysis-driven proton pumps. V-ATPases are the primary source of organellar acidification in all eukaryotes, making them essential for many fundamental cellular processes. Enzymatic activity can be modulated by regulated and reversible disassembly of the complex, and several subunits of mammalian V-ATPase have multiple isoforms that are differentially localized. Although the biochemical properties of the different isoforms are currently unknown, mutations in specific subunit isoforms have been associated with various diseases, making V-ATPases potential drug targets. V-ATPase structure and activity have been best characterized in Saccharomyces cerevisiae, where recent structures have revealed details about the dynamics of the enzyme, the proton translocation pathway, and conformational changes associated with regulated disassembly and autoinhibition.
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Affiliation(s)
- Thamiya Vasanthakumar
- The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, The University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - John L Rubinstein
- The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, The University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Medical Biophysics, The University of Toronto, Toronto, ON M5G 1L7, Canada.
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10
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Jaskolka MC, Kane PM. Interaction between the yeast RAVE complex and Vph1-containing V o sectors is a central glucose-sensitive interaction required for V-ATPase reassembly. J Biol Chem 2020; 295:2259-2269. [PMID: 31941791 DOI: 10.1074/jbc.ra119.011522] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 01/02/2020] [Indexed: 12/12/2022] Open
Abstract
The yeast vacuolar H+-ATPase (V-ATPase) of budding yeast (Saccharomyces cerevisiae) is regulated by reversible disassembly. Disassembly inhibits V-ATPase activity under low-glucose conditions by releasing peripheral V1 subcomplexes from membrane-bound Vo subcomplexes. V-ATPase reassembly and reactivation requires intervention of the conserved regulator of H+-ATPase of vacuoles and endosomes (RAVE) complex, which binds to cytosolic V1 subcomplexes and assists reassembly with integral membrane Vo complexes. Consistent with its role, the RAVE complex itself is reversibly recruited to the vacuolar membrane by glucose, but the requirements for its recruitment are not understood. We demonstrate here that RAVE recruitment to the membrane does not require an interaction with V1 Glucose-dependent RAVE localization to the vacuolar membrane required only intact Vo complexes containing the Vph1 subunit, suggesting that the RAVE-Vo interaction is glucose-dependent. We identified a short conserved sequence in the center of the RAVE subunit Rav1 that is essential for the interaction with Vph1 in vivo and in vitro Mutations in this region resulted in the temperature- and pH-dependent growth phenotype characteristic of ravΔ mutants. However, this region did not account for glucose sensitivity of the Rav1-Vph1 interaction. We quantitated glucose-dependent localization of a GFP-tagged RAVE subunit to the vacuolar membrane in several mutants previously implicated in altering V-ATPase assembly state or glucose-induced assembly. RAVE localization did not correlate with V-ATPase assembly levels reported previously in these mutants, highlighting both the catalytic nature of RAVE's role in V-ATPase assembly and the likelihood of glucose signaling to RAVE independently of V1.
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Affiliation(s)
- Michael C Jaskolka
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210.
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11
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Sharma S, Oot RA, Khan MM, Wilkens S. Functional reconstitution of vacuolar H +-ATPase from V o proton channel and mutant V 1-ATPase provides insight into the mechanism of reversible disassembly. J Biol Chem 2019; 294:6439-6449. [PMID: 30792311 DOI: 10.1074/jbc.ra119.007577] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 02/10/2019] [Indexed: 12/12/2022] Open
Abstract
The vacuolar H+-ATPase (V-ATPase; V1Vo-ATPase) is an ATP-dependent proton pump that acidifies subcellular compartments in all eukaryotic organisms. V-ATPase activity is regulated by reversible disassembly into autoinhibited V1-ATPase and Vo proton channel subcomplexes, a process that is poorly understood on the molecular level. V-ATPase is a rotary motor, and recent structural analyses have revealed different rotary states for disassembled V1 and Vo, a mismatch that is likely responsible for their inability to reconstitute into holo V-ATPase in vitro Here, using the model organism Saccharomyces cerevisiae, we show that a key impediment for binding of V1 to Vo is the conformation of the inhibitory C-terminal domain of subunit H (HCT). Using biolayer interferometry and biochemical analyses of purified mutant V1-ATPase and Vo proton channel reconstituted into vacuolar lipid-containing nanodiscs, we further demonstrate that disruption of HCT's V1-binding site facilitates assembly of a functionally coupled and stable V1Vo-ATPase. Unlike WT, this mutant enzyme was resistant to MgATP hydrolysis-induced dissociation, further highlighting HCT's role in the mechanism of V-ATPase regulation. Our findings provide key insight into the molecular events underlying regulation of V-ATPase activity by reversible disassembly.
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Affiliation(s)
- Stuti Sharma
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Rebecca A Oot
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Md Murad Khan
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Stephan Wilkens
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
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12
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Hayek SR, Rane HS, Parra KJ. Reciprocal Regulation of V-ATPase and Glycolytic Pathway Elements in Health and Disease. Front Physiol 2019; 10:127. [PMID: 30828305 PMCID: PMC6384264 DOI: 10.3389/fphys.2019.00127] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/31/2019] [Indexed: 12/24/2022] Open
Abstract
The ability of cells to adapt to fluctuations in glucose availability is crucial for their survival and involves the vacuolar proton-translocating ATPase (V-ATPase), a proton pump found in all eukaryotes. V-ATPase hydrolyzes ATP via its V1 domain and uses the energy released to transport protons across membranes via its Vo domain. This activity is critical for pH homeostasis and generation of a membrane potential that drives cellular metabolism. A number of stimuli have been reported to alter V-ATPase assembly in yeast and higher eukaryotes. Glucose flux is one of the strongest and best-characterized regulators of V-ATPase; this review highlights current models explaining how glycolysis and V-ATPase are coordinated in both the Saccharomyces cerevisiae model fungus and in mammalian systems. Glucose-dependent assembly and trafficking of V-ATPase, V-ATPase-dependent modulations in glycolysis, and the recent discovery that glucose signaling through V-ATPase acts as a molecular switch to dictate anabolic versus catabolic metabolism are discussed. Notably, metabolic plasticity and altered glycolytic flux are critical drivers of numerous human pathologies, and the expression and activity of V-ATPase is often altered in disease states or can be pharmacologically manipulated as treatment. This overview will specifically discuss connections between V-ATPase and glycolysis in cancer.
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Affiliation(s)
- Summer R Hayek
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Hallie S Rane
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Karlett J Parra
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
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13
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Specific V-ATPase expression sub-classifies IDHwt lower-grade gliomas and impacts glioma growth in vivo. EBioMedicine 2019; 41:214-224. [PMID: 30737087 PMCID: PMC6441867 DOI: 10.1016/j.ebiom.2019.01.052] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 01/24/2019] [Accepted: 01/25/2019] [Indexed: 12/27/2022] Open
Abstract
Background Cancer cells use specific V-ATPase subunits to activate oncogenic pathways. Therefore, we investigated V-ATPase deregulation in aggressive gliomas and associated signaling. Methods V-ATPase genes expression and associated pathways were analyzed in different series of glioma available from public databases, as well as in patients' cohort. Activation of pathways was analyzed at gene and protein expression levels. A genetic model of glioma in Drosophila melanogaster and mice with GBM patients-derived orthotopic xenografts were used as in vivo models of disease. Findings GBM and recurrent gliomas display a specific V-ATPase signature. Such signature resolves the heterogeneous class of IDH-wild type lower-grade gliomas, identifying the patients with worse prognosis independently from clinical and molecular features (p = 0·03, by Cox proportional-hazards model). In vivo, V-ATPase subunits deregulation significantly impacts tumor growth and proliferation. At the molecular level, GBM-like V-ATPase expression correlates with upregulation of Homeobox genes. Interpretation Our data identify a V-ATPase signature that accompanies glioma aggressiveness and suggest new entry points for glioma stratification and follow-up. Fund This work was supported by Fondazione Cariplo (2014–1148 to VV), Fondazione IRCCS Ca' Granda, and Fondazione INGM Grant in Molecular Medicine 2014 (to VV).
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14
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Harrison MA, Muench SP. The Vacuolar ATPase - A Nano-scale Motor That Drives Cell Biology. Subcell Biochem 2018; 87:409-459. [PMID: 29464568 DOI: 10.1007/978-981-10-7757-9_14] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The vacuolar H+-ATPase (V-ATPase) is a ~1 MDa membrane protein complex that couples the hydrolysis of cytosolic ATP to the transmembrane movement of protons. In essentially all eukaryotic cells, this acid pumping function plays critical roles in the acidification of endosomal/lysosomal compartments and hence in transport, recycling and degradative pathways. It is also important in acid extrusion across the plasma membrane of some cells, contributing to homeostatic control of cytoplasmic pH and maintenance of appropriate extracellular acidity. The complex, assembled from up to 30 individual polypeptides, operates as a molecular motor with rotary mechanics. Historically, structural inferences about the eukaryotic V-ATPase and its subunits have been made by comparison to the structures of bacterial homologues. However, more recently, we have developed a much better understanding of the complete structure of the eukaryotic complex, in particular through advances in cryo-electron microscopy. This chapter explores these recent developments, and examines what they now reveal about the catalytic mechanism of this essential proton pump and how its activity might be regulated in response to cellular signals.
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Affiliation(s)
- Michael A Harrison
- School of Biomedical Sciences, Faculty of Biological Sciences, The University of Leeds, Leeds, UK.
| | - Steven P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences, The University of Leeds, Leeds, UK
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15
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Sharma S, Oot RA, Wilkens S. MgATP hydrolysis destabilizes the interaction between subunit H and yeast V 1-ATPase, highlighting H's role in V-ATPase regulation by reversible disassembly. J Biol Chem 2018; 293:10718-10730. [PMID: 29754144 DOI: 10.1074/jbc.ra118.002951] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 04/22/2018] [Indexed: 01/01/2023] Open
Abstract
Vacuolar H+-ATPases (V-ATPases; V1Vo-ATPases) are rotary-motor proton pumps that acidify intracellular compartments and, in some tissues, the extracellular space. V-ATPase is regulated by reversible disassembly into autoinhibited V1-ATPase and Vo proton channel sectors. An important player in V-ATPase regulation is subunit H, which binds at the interface of V1 and Vo H is required for MgATPase activity in holo-V-ATPase but also for stabilizing the MgADP-inhibited state in membrane-detached V1 However, how H fulfills these two functions is poorly understood. To characterize the H-V1 interaction and its role in reversible disassembly, we determined binding affinities of full-length H and its N-terminal domain (HNT) for an isolated heterodimer of subunits E and G (EG), the N-terminal domain of subunit a (aNT), and V1 lacking subunit H (V1ΔH). Using isothermal titration calorimetry (ITC) and biolayer interferometry (BLI), we show that HNT binds EG with moderate affinity, that full-length H binds aNT weakly, and that both H and HNT bind V1ΔH with high affinity. We also found that only one molecule of HNT binds V1ΔH with high affinity, suggesting conformational asymmetry of the three EG heterodimers in V1ΔH. Moreover, MgATP hydrolysis-driven conformational changes in V1 destabilized the interaction of H or HNT with V1ΔH, suggesting an interplay between MgADP inhibition and subunit H. Our observation that H binding is affected by MgATP hydrolysis in V1 points to H's role in the mechanism of reversible disassembly.
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Affiliation(s)
- Stuti Sharma
- From the Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, New York 13210
| | - Rebecca A Oot
- From the Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, New York 13210
| | - Stephan Wilkens
- From the Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, New York 13210
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16
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Farsi Z, Gowrisankaran S, Krunic M, Rammner B, Woehler A, Lafer EM, Mim C, Jahn R, Milosevic I. Clathrin coat controls synaptic vesicle acidification by blocking vacuolar ATPase activity. eLife 2018; 7:32569. [PMID: 29652249 PMCID: PMC5935483 DOI: 10.7554/elife.32569] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 04/07/2018] [Indexed: 12/14/2022] Open
Abstract
Newly-formed synaptic vesicles (SVs) are rapidly acidified by vacuolar adenosine triphosphatases (vATPases), generating a proton electrochemical gradient that drives neurotransmitter loading. Clathrin-mediated endocytosis is needed for the formation of new SVs, yet it is unclear when endocytosed vesicles acidify and refill at the synapse. Here, we isolated clathrin-coated vesicles (CCVs) from mouse brain to measure their acidification directly at the single vesicle level. We observed that the ATP-induced acidification of CCVs was strikingly reduced in comparison to SVs. Remarkably, when the coat was removed from CCVs, uncoated vesicles regained ATP-dependent acidification, demonstrating that CCVs contain the functional vATPase, yet its function is inhibited by the clathrin coat. Considering the known structures of the vATPase and clathrin coat, we propose a model in which the formation of the coat surrounds the vATPase and blocks its activity. Such inhibition is likely fundamental for the proper timing of SV refilling.
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Affiliation(s)
- Zohreh Farsi
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Sindhuja Gowrisankaran
- Synaptic Vesicle Dynamics Group, European Neuroscience Institute, University Medical Center Göttingen, Göttingen, Germany
| | - Matija Krunic
- Synaptic Vesicle Dynamics Group, European Neuroscience Institute, University Medical Center Göttingen, Göttingen, Germany
| | | | - Andrew Woehler
- Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Eileen M Lafer
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States.,Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, United States
| | - Carsten Mim
- Department for Biomedical Engineering and Health Solutions, Kungliga Tekniska Högskolan, Huddinge, Sweden.,Department of Biosciences and Nutrition, Karolinska Institute, Huddinge, Sweden
| | - Reinhard Jahn
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Ira Milosevic
- Synaptic Vesicle Dynamics Group, European Neuroscience Institute, University Medical Center Göttingen, Göttingen, Germany
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17
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Rotating with the brakes on and other unresolved features of the vacuolar ATPase. Biochem Soc Trans 2017; 44:851-5. [PMID: 27284051 PMCID: PMC4900747 DOI: 10.1042/bst20160043] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Indexed: 12/31/2022]
Abstract
The rotary ATPase family comprises the ATP synthase (F-ATPase), vacuolar ATPase (V-ATPase) and archaeal ATPase (A-ATPase). These either predominantly utilize a proton gradient for ATP synthesis or use ATP to produce a proton gradient, driving secondary transport and acidifying organelles. With advances in EM has come a significant increase in our understanding of the rotary ATPase family. Following the sub nm resolution reconstructions of both the F- and V-ATPases, the secondary structure organization of the elusive subunit a has now been resolved, revealing a novel helical arrangement. Despite these significant developments in our understanding of the rotary ATPases, there are still a number of unresolved questions about the mechanism, regulation and overall architecture, which this mini-review aims to highlight and discuss.
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18
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Oot RA, Couoh-Cardel S, Sharma S, Stam NJ, Wilkens S. Breaking up and making up: The secret life of the vacuolar H + -ATPase. Protein Sci 2017; 26:896-909. [PMID: 28247968 DOI: 10.1002/pro.3147] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 02/21/2017] [Indexed: 01/24/2023]
Abstract
The vacuolar ATPase (V-ATPase; V1 Vo -ATPase) is a large multisubunit proton pump found in the endomembrane system of all eukaryotic cells where it acidifies the lumen of subcellular organelles including lysosomes, endosomes, the Golgi apparatus, and clathrin-coated vesicles. V-ATPase function is essential for pH and ion homeostasis, protein trafficking, endocytosis, mechanistic target of rapamycin (mTOR), and Notch signaling, as well as hormone secretion and neurotransmitter release. V-ATPase can also be found in the plasma membrane of polarized animal cells where its proton pumping function is involved in bone remodeling, urine acidification, and sperm maturation. Aberrant (hypo or hyper) activity has been associated with numerous human diseases and the V-ATPase has therefore been recognized as a potential drug target. Recent progress with moderate to high-resolution structure determination by cryo electron microscopy and X-ray crystallography together with sophisticated single-molecule and biochemical experiments have provided a detailed picture of the structure and unique mode of regulation of the V-ATPase. This review summarizes the recent advances, focusing on the structural and biophysical aspects of the field.
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Affiliation(s)
- Rebecca A Oot
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, 13210
| | - Sergio Couoh-Cardel
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, 13210
| | - Stuti Sharma
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, 13210
| | - Nicholas J Stam
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, 13210
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, 13210
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19
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Oot RA, Kane PM, Berry EA, Wilkens S. Crystal structure of yeast V1-ATPase in the autoinhibited state. EMBO J 2016; 35:1694-706. [PMID: 27295975 DOI: 10.15252/embj.201593447] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 05/12/2016] [Indexed: 01/23/2023] Open
Abstract
Vacuolar ATPases (V-ATPases) are essential proton pumps that acidify the lumen of subcellular organelles in all eukaryotic cells and the extracellular space in some tissues. V-ATPase activity is regulated by a unique mechanism referred to as reversible disassembly, wherein the soluble catalytic sector, V1, is released from the membrane and its MgATPase activity silenced. The crystal structure of yeast V1 presented here shows that activity silencing involves a large conformational change of subunit H, with its C-terminal domain rotating ~150° from a position near the membrane in holo V-ATPase to a position at the bottom of V1 near an open catalytic site. Together with biochemical data, the structure supports a mechanistic model wherein subunit H inhibits ATPase activity by stabilizing an open catalytic site that results in tight binding of inhibitory ADP at another site.
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Affiliation(s)
- Rebecca A Oot
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Edward A Berry
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
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20
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Chan CY, Dominguez D, Parra KJ. Regulation of Vacuolar H+-ATPase (V-ATPase) Reassembly by Glycolysis Flow in 6-Phosphofructo-1-kinase (PFK-1)-deficient Yeast Cells. J Biol Chem 2016; 291:15820-9. [PMID: 27226568 DOI: 10.1074/jbc.m116.717488] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Indexed: 01/21/2023] Open
Abstract
Yeast 6-phosphofructo-1-kinase (PFK-1) has two subunits, Pfk1p and Pfk2p. Deletion of Pfk2p alters glucose-dependent V-ATPase reassembly and vacuolar acidification (Chan, C. Y., and Parra, K. J. (2014) Yeast phosphofructokinase-1 subunit Pfk2p is necessary for pH homeostasis and glucose-dependent vacuolar ATPase reassembly. J. Biol. Chem. 289, 19448-19457). This study capitalized on the mechanisms suppressing vacuolar H(+)-ATPase (V-ATPase) in pfk2Δ to gain new knowledge of the mechanisms underlying glucose-dependent V-ATPase regulation. Because V-ATPase is fully assembled in pfk2Δ, and glycolysis partially suppressed at steady state, we manipulated glycolysis and assessed its direct involvement on V-ATPase function. At steady state, the ratio of proton transport to ATP hydrolysis increased 24% after increasing the glucose concentration from 2% to 4% to enhance the glycolysis flow in pfk2Δ. Tighter coupling restored vacuolar pH when glucose was abundant and glycolysis operated below capacity. After readdition of glucose to glucose-deprived cells, glucose-dependent V1Vo reassembly was proportional to the glycolysis flow. Readdition of 2% glucose to pfk2Δ cells, which restored 62% of ethanol concentration, led to equivalent 60% V1Vo reassembly levels. Steady-state level of assembly (100% reassembly) was reached at 4% glucose when glycolysis reached a threshold in pfk2Δ (≥40% the wild-type flow). At 4% glucose, the level of Pfk1p co-immunoprecipitated with V-ATPase decreased 58% in pfk2Δ, suggesting that Pfk1p binding to V-ATPase may be inhibitory in the mutant. We concluded that V-ATPase activity at steady state and V-ATPase reassembly after readdition of glucose to glucose-deprived cells are controlled by the glycolysis flow. We propose a new mechanism by which glucose regulates V-ATPase catalytic activity that occurs at steady state without changing V1Vo assembly.
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Affiliation(s)
- Chun-Yuan Chan
- From the Department of Biochemistry and Molecular Biology, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Dennis Dominguez
- From the Department of Biochemistry and Molecular Biology, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
| | - Karlett J Parra
- From the Department of Biochemistry and Molecular Biology, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131
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21
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Cotter K, Stransky L, McGuire C, Forgac M. Recent Insights into the Structure, Regulation, and Function of the V-ATPases. Trends Biochem Sci 2016; 40:611-622. [PMID: 26410601 DOI: 10.1016/j.tibs.2015.08.005] [Citation(s) in RCA: 174] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 08/06/2015] [Accepted: 08/07/2015] [Indexed: 10/23/2022]
Abstract
The vacuolar (H(+))-ATPases (V-ATPases) are ATP-dependent proton pumps that acidify intracellular compartments and are also present at the plasma membrane. They function in such processes as membrane traffic, protein degradation, virus and toxin entry, bone resorption, pH homeostasis, and tumor cell invasion. V-ATPases are large multisubunit complexes, composed of an ATP-hydrolytic domain (V1) and a proton translocation domain (V0), and operate by a rotary mechanism. This review focuses on recent insights into their structure and mechanism, the mechanisms that regulate V-ATPase activity (particularly regulated assembly and trafficking), and the role of V-ATPases in processes such as cell signaling and cancer. These developments have highlighted the potential of V-ATPases as a therapeutic target in a variety of human diseases.
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Affiliation(s)
- Kristina Cotter
- Program in Cellular and Molecular Physiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
| | - Laura Stransky
- Program in Cellular and Molecular Physiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
| | - Christina McGuire
- Program in Biochemistry, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
| | - Michael Forgac
- Program in Cellular and Molecular Physiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA; Program in Biochemistry, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA; Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
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22
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Couoh-Cardel S, Milgrom E, Wilkens S. Affinity Purification and Structural Features of the Yeast Vacuolar ATPase Vo Membrane Sector. J Biol Chem 2015; 290:27959-71. [PMID: 26416888 DOI: 10.1074/jbc.m115.662494] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Indexed: 12/27/2022] Open
Abstract
The membrane sector (Vo) of the proton pumping vacuolar ATPase (V-ATPase, V1Vo-ATPase) from Saccharomyces cerevisiae was purified to homogeneity, and its structure was characterized by EM of single molecules and two-dimensional crystals. Projection images of negatively stained Vo two-dimensional crystals showed a ring-like structure with a large asymmetric mass at the periphery of the ring. A cryo-EM reconstruction of Vo from single-particle images showed subunits a and d in close contact on the cytoplasmic side of the proton channel. A comparison of three-dimensional reconstructions of free Vo and Vo as part of holo V1Vo revealed that the cytoplasmic N-terminal domain of subunit a (aNT) must undergo a large conformational change upon enzyme disassembly or (re)assembly from Vo, V1, and subunit C. Isothermal titration calorimetry using recombinant subunit d and aNT revealed that the two proteins bind each other with a Kd of ~5 μm. Treatment of the purified Vo sector with 1-palmitoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] resulted in selective release of subunit d, allowing purification of a VoΔd complex. Passive proton translocation assays revealed that both Vo and VoΔd are impermeable to protons. We speculate that the structural change in subunit a upon release of V1 from Vo during reversible enzyme dissociation plays a role in blocking passive proton translocation across free Vo and that the interaction between aNT and d seen in free Vo functions to stabilize the Vo sector for efficient reassembly of V1Vo.
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Affiliation(s)
- Sergio Couoh-Cardel
- From the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210
| | - Elena Milgrom
- From the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210
| | - Stephan Wilkens
- From the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210
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23
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Smardon AM, Nasab ND, Tarsio M, Diakov TT, Kane PM. Molecular Interactions and Cellular Itinerary of the Yeast RAVE (Regulator of the H+-ATPase of Vacuolar and Endosomal Membranes) Complex. J Biol Chem 2015; 290:27511-23. [PMID: 26405040 DOI: 10.1074/jbc.m115.667634] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Indexed: 12/11/2022] Open
Abstract
The RAVE complex (regulator of the H(+)-ATPase of vacuolar and endosomal membranes) is required for biosynthetic assembly and glucose-stimulated reassembly of the yeast vacuolar H(+)-ATPase (V-ATPase). Yeast RAVE contains three subunits: Rav1, Rav2, and Skp1. Rav1 is the largest subunit, and it binds Rav2 and Skp1 of RAVE; the E, G, and C subunits of the V-ATPase peripheral V1 sector; and Vph1 of the membrane Vo sector. We identified Rav1 regions required for interaction with its binding partners through deletion analysis, co-immunoprecipitation, two-hybrid assay, and pulldown assays with expressed proteins. We find that Skp1 binding requires sequences near the C terminus of Rav1, V1 subunits E and C bind to a conserved region in the C-terminal half of Rav1, and the cytosolic domain of Vph1 binds near the junction of the Rav1 N- and C-terminal halves. In contrast, Rav2 binds to the N-terminal domain of Rav1, which can be modeled as a double β-propeller. Only the V1 C subunit binds to both Rav1 and Rav2. Using GFP-tagged RAVE subunits in vivo, we demonstrate glucose-dependent association of RAVE with the vacuolar membrane, consistent with its role in glucose-dependent V-ATPase assembly. It is known that V1 subunit C localizes to the V1-Vo interface in assembled V-ATPase complexes and is important in regulated disassembly of V-ATPases. We propose that RAVE cycles between cytosol and vacuolar membrane in a glucose-dependent manner, positioning V1 and V0 subcomplexes and orienting the V1 C subunit to promote assembly.
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Affiliation(s)
- Anne M Smardon
- From the Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Negin Dehdar Nasab
- From the Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Maureen Tarsio
- From the Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Theodore T Diakov
- From the Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Patricia M Kane
- From the Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
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24
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Saccharomyces cerevisiae vacuolar H+-ATPase regulation by disassembly and reassembly: one structure and multiple signals. EUKARYOTIC CELL 2014; 13:706-14. [PMID: 24706019 DOI: 10.1128/ec.00050-14] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Vacuolar H(+)-ATPases (V-ATPases) are highly conserved ATP-driven proton pumps responsible for acidification of intracellular compartments. V-ATPase proton transport energizes secondary transport systems and is essential for lysosomal/vacuolar and endosomal functions. These dynamic molecular motors are composed of multiple subunits regulated in part by reversible disassembly, which reversibly inactivates them. Reversible disassembly is intertwined with glycolysis, the RAS/cyclic AMP (cAMP)/protein kinase A (PKA) pathway, and phosphoinositides, but the mechanisms involved are elusive. The atomic- and pseudo-atomic-resolution structures of the V-ATPases are shedding light on the molecular dynamics that regulate V-ATPase assembly. Although all eukaryotic V-ATPases may be built with an inherent capacity to reversibly disassemble, not all do so. V-ATPase subunit isoforms and their interactions with membrane lipids and a V-ATPase-exclusive chaperone influence V-ATPase assembly. This minireview reports on the mechanisms governing reversible disassembly in the yeast Saccharomyces cerevisiae, keeping in perspective our present understanding of the V-ATPase architecture and its alignment with the cellular processes and signals involved.
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25
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Marshansky V, Rubinstein JL, Grüber G. Eukaryotic V-ATPase: novel structural findings and functional insights. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:857-79. [PMID: 24508215 DOI: 10.1016/j.bbabio.2014.01.018] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Revised: 12/25/2013] [Accepted: 01/27/2014] [Indexed: 02/06/2023]
Abstract
The eukaryotic V-type adenosine triphosphatase (V-ATPase) is a multi-subunit membrane protein complex that is evolutionarily related to F-type adenosine triphosphate (ATP) synthases and A-ATP synthases. These ATPases/ATP synthases are functionally conserved and operate as rotary proton-pumping nano-motors, invented by Nature billions of years ago. In the first part of this review we will focus on recent structural findings of eukaryotic V-ATPases and discuss the role of different subunits in the function of the V-ATPase holocomplex. Despite structural and functional similarities between rotary ATPases, the eukaryotic V-ATPases are the most complex enzymes that have acquired some unconventional cellular functions during evolution. In particular, the novel roles of V-ATPases in the regulation of cellular receptors and their trafficking via endocytotic and exocytotic pathways were recently uncovered. In the second part of this review we will discuss these unique roles of V-ATPases in modulation of function of cellular receptors, involved in the development and progression of diseases such as cancer and diabetes as well as neurodegenerative and kidney disorders. Moreover, it was recently revealed that the V-ATPase itself functions as an evolutionarily conserved pH sensor and receptor for cytohesin-2/Arf-family GTP-binding proteins. Thus, in the third part of the review we will evaluate the structural basis for and functional insights into this novel concept, followed by the analysis of the potentially essential role of V-ATPase in the regulation of this signaling pathway in health and disease. Finally, future prospects for structural and functional studies of the eukaryotic V-ATPase will be discussed.
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Affiliation(s)
- Vladimir Marshansky
- Center for Systems Biology, Program in Membrane Biology, Division of Nephrology, Simches Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA; Department of Medicine, Harvard Medical School, Boston, MA 02114, USA; Kadmon Pharmaceuticals Corporation, Alexandria Center for Life Science, 450 East 29th Street, New York, NY 10016, USA.
| | - John L Rubinstein
- Molecular Structure and Function Program, The Hospital for Sick Children Research Institute, University of Toronto, Toronto, ON M5G 1X8, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5G 1X8, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1X8, Canada
| | - Gerhard Grüber
- Nanyang Technological University, Division of Structural Biology and Biochemistry, School of Biological Sciences, Singapore 637551, Republic of Singapore; Bioinformatics Institute, A(⁎)STAR, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
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26
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Smardon AM, Diab HI, Tarsio M, Diakov TT, Nasab ND, West RW, Kane PM. The RAVE complex is an isoform-specific V-ATPase assembly factor in yeast. Mol Biol Cell 2013; 25:356-67. [PMID: 24307682 PMCID: PMC3907276 DOI: 10.1091/mbc.e13-05-0231] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Vacuolar H+-ATPases (V-ATPases) acidify multiple organelles, and subunit isoforms help impart organelle-specific regulation of acidification. The regulator of ATPase of vacuoles and endosomes (RAVE) complex regulates organelle acidification by promoting V-ATPase assembly. This work demonstrates that RAVE is the first identified isoform-specific V-ATPase assembly factor required for control of vacuolar acidification. The regulator of ATPase of vacuoles and endosomes (RAVE) complex is implicated in vacuolar H+-translocating ATPase (V-ATPase) assembly and activity. In yeast, rav1∆ mutants exhibit a Vma− growth phenotype characteristic of loss of V-ATPase activity only at high temperature. Synthetic genetic analysis identified mutations that exhibit a full, temperature-independent Vma− growth defect when combined with the rav1∆ mutation. These include class E vps mutations, which compromise endosomal sorting. The synthetic Vma− growth defect could not be attributed to loss of vacuolar acidification in the double mutants, as there was no vacuolar acidification in the rav1∆ mutant. The yeast V-ATPase a subunit is present as two isoforms, Stv1p in Golgi and endosomes and Vph1p in vacuoles. Rav1p interacts directly with the N-terminal domain of Vph1p. STV1 overexpression suppressed the growth defects of both rav1∆ and rav1∆vph1∆, and allowed RAVE-independent assembly of active Stv1p-containing V-ATPases in vacuoles. Mutations causing synthetic genetic defects in combination with rav1∆ perturbed the normal localization of Stv1–green fluorescent protein. We propose that RAVE is necessary for assembly of Vph1-containing V-ATPase complexes but not Stv1-containing complexes. Synthetic Vma− phenotypes arise from defects in Vph1p-containing complexes caused by rav1∆, combined with defects in Stv1p-containing V-ATPases caused by the second mutation. Thus RAVE is the first isoform-specific V-ATPase assembly factor.
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Affiliation(s)
- Anne M Smardon
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210
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27
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Muench SP, Scheres SHW, Huss M, Phillips C, Vitavska O, Wieczorek H, Trinick J, Harrison MA. Subunit positioning and stator filament stiffness in regulation and power transmission in the V1 motor of the Manduca sexta V-ATPase. J Mol Biol 2013; 426:286-300. [PMID: 24075871 PMCID: PMC3899036 DOI: 10.1016/j.jmb.2013.09.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 09/04/2013] [Accepted: 09/05/2013] [Indexed: 12/01/2022]
Abstract
The vacuolar H+-ATPase (V-ATPase) is an ATP-driven proton pump essential to the function of eukaryotic cells. Its cytoplasmic V1 domain is an ATPase, normally coupled to membrane-bound proton pump Vo via a rotary mechanism. How these asymmetric motors are coupled remains poorly understood. Low energy status can trigger release of V1 from the membrane and curtail ATP hydrolysis. To investigate the molecular basis for these processes, we have carried out cryo-electron microscopy three-dimensional reconstruction of deactivated V1 from Manduca sexta. In the resulting model, three peripheral stalks that are parts of the mechanical stator of the V-ATPase are clearly resolved as unsupported filaments in the same conformations as in the holoenzyme. They are likely therefore to have inherent stiffness consistent with a role as flexible rods in buffering elastic power transmission between the domains of the V-ATPase. Inactivated V1 adopted a homogeneous resting state with one open active site adjacent to the stator filament normally linked to the H subunit. Although present at 1:1 stoichiometry with V1, both recombinant subunit C reconstituted with V1 and its endogenous subunit H were poorly resolved in three-dimensional reconstructions, suggesting structural heterogeneity in the region at the base of V1 that could indicate positional variability. If the position of H can vary, existing mechanistic models of deactivation in which it binds to and locks the axle of the V-ATPase rotary motor would need to be re-evaluated. Dissociation of vacuolar H+-ATPase domains deactivates its V1 motor. V1 has one “open” catalytic site linked to the stator filament bound by subunit H. Movement of subunit H to prevent rotary catalysis is possible. Three stator filaments project from deactivated V1, indicating inherent stiffness. This work gives new insight into energetic coupling and control in V-ATPases.
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Affiliation(s)
- Stephen P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Sjors H W Scheres
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Markus Huss
- Abteilung Tierphysiologie, Fachbereich Biologie/Chemie, Universität Osnabrück, 49069 Osnabrück, Germany
| | - Clair Phillips
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Olga Vitavska
- Abteilung Tierphysiologie, Fachbereich Biologie/Chemie, Universität Osnabrück, 49069 Osnabrück, Germany
| | - Helmut Wieczorek
- Abteilung Tierphysiologie, Fachbereich Biologie/Chemie, Universität Osnabrück, 49069 Osnabrück, Germany
| | - John Trinick
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Michael A Harrison
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
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28
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Liberman R, Cotter K, Baleja JD, Forgac M. Structural analysis of the N-terminal domain of subunit a of the yeast vacuolar ATPase (V-ATPase) using accessibility of single cysteine substitutions to chemical modification. J Biol Chem 2013; 288:22798-808. [PMID: 23740254 DOI: 10.1074/jbc.m113.460295] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The vacuolar ATPase (V-ATPase) is a multisubunit complex that carries out ATP-driven proton transport. It is composed of a peripheral V1 domain that hydrolyzes ATP and an integral V0 domain that translocates protons. Subunit a is a 100-kDa integral membrane protein (part of V0) that possesses an N-terminal cytoplasmic domain and a C-terminal hydrophobic domain. Although the C-terminal domain functions in proton transport, the N-terminal domain is critical for intracellular targeting and regulation of V-ATPase assembly. Despite its importance, there is currently no high resolution structure for subunit a of the V-ATPase. Recently, the crystal structure of the N-terminal domain of the related subunit I from the archaebacterium Meiothermus ruber was reported. We have used homology modeling to construct a model of the N-terminal domain of Vph1p, one of two isoforms of subunit a expressed in yeast. To test this model, unique cysteine residues were introduced into a Cys-less form of Vph1p and their accessibility to modification by the sulfhydryl reagent 3-(N-maleimido-propionyl) biocytin (MPB) was determined. In addition, accessibility of introduced cysteine residues to MPB modification was compared in the V1V0 complex and the free V0 domain to identify residues protected from modification by the presence of V1. The results provide an experimental test of the proposed model and have identified regions of the N-terminal domain of subunit a that likely serve as interfacial contact sites with the peripheral V1 domain. The possible significance of these results for in vivo regulation of V-ATPase assembly is discussed.
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Affiliation(s)
- Rachel Liberman
- Department of Molecular Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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29
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Petzoldt AG, Gleixner EM, Fumagalli A, Vaccari T, Simons M. Elevated expression of the V-ATPase C subunit triggers JNK-dependent cell invasion and overgrowth in a Drosophila epithelium. Dis Model Mech 2013; 6:689-700. [PMID: 23335205 PMCID: PMC3634652 DOI: 10.1242/dmm.010660] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The C subunit of the vacuolar H+-ATPase or V-ATPase regulates the activity and assembly of the proton pump at cellular membranes. It has been shown to be strongly upregulated in oral squamous cell carcinoma, a highly metastatic epithelial cancer. In addition, increased V-ATPase activity appears to correlate with invasiveness of cancer cells, but the underlying mechanism is largely unknown. Using the Drosophila wing imaginal epithelium as an in vivo model system, we demonstrate that overexpression of Vha44, the Drosophila orthologue of the C subunit, causes a tumor-like tissue transformation in cells of the wing epithelium. Overexpressing cells are excluded from the epithelium and acquire invasive properties while displaying high apoptotic rates. Blocking apoptosis in these cells unmasks a strong proliferation stimulus, leading to overgrowth. Furthermore, we show that excess Vha44 greatly increases acidification of endocytic compartments and interferes with endosomal trafficking. As a result, cargoes such as GFP-Lamp1 and Notch accumulate in highly acidified enlarged endolysosomal compartments. Consistent with previous reports on the endocytic activation of Eiger/JNK signaling, we find that V-ATPase stimulation by Vha44 causes JNK signaling activation whereas downmodulation of JNK signaling rescues the invasive phenotypes. In summary, our in vivo-findings demonstrate that increased levels of V-ATPase C subunit induce a Eiger/JNK-dependent cell transformation within an epithelial organ that recapitulates early carcinoma stages.
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Affiliation(s)
- Astrid G Petzoldt
- Center for Systems Biology (ZBSA), University of Freiburg, Habsburgerstr. 49, 79104 Freiburg, Germany
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30
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Ribeiro CC, Monteiro RM, Freitas FP, Retamal C, Teixeira LRS, Palma LM, Silva FE, Façanha AR, Okorokova-Façanha AL, Okorokov LA. Extracellular glucose increases the coupling capacity of the yeast V H+-ATPase and the resistance of its H+ transport activity to nitrate inhibition. PLoS One 2012; 7:e49580. [PMID: 23189149 PMCID: PMC3506656 DOI: 10.1371/journal.pone.0049580] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 10/11/2012] [Indexed: 11/18/2022] Open
Abstract
V H(+)-ATPase has an important role in a variety of key physiological processes. This enzyme is reversibly activated/partly inactivated by the addition/exhaustion of extracellular glucose. The current model of its regulation assumes the reversible disassembly/reassembly of ∼60-70% of the V1 and V0 membrane complexes, which are responsible for ATP hydrolysis and H(+) conductance, respectively. The number of assembled complexes determines the pump activity because disassembled complexes are inactive. The model predicts the identical catalytic properties for the activated and semi-active enzymes molecules. To verify the model predictions we have isolated total membranes from yeast spheroplasts that were pre-incubated either with or without glucose. Nitrate treatment of membranes revealed the similar ATPase inhibition for two enzyme states, suggesting that they have identical structures that are essential for ATP hydrolysis. However, H(+) transport was inhibited more than the ATPase activities, indicating a nitrate uncoupling action, which was significantly higher for the nonactivated enzyme. This finding suggests that the structure of the non-activated enzyme, which is essential for H(+) transport, is less stable than that of the activated enzyme. Moreover, the glucose activation of the pump increases i) its coupling capacity; ii) its K(M) for ATP hydrolysis and ATP affinity for H(+) transport; iii) the Vmax for H(+) transport in comparison with the Vmax for ATP hydrolysis and iv) the immune reactivity of catalytic subunit A and regulatory subunit B by 9.3 and 2.4 times, respectively. The protein content of subunits A and B was not changed by extracellular glucose. We propose that instead of the dissociation/reassociation of complexes V1 and V0, changes in the extracellular glucose concentration cause reversible and asymmetrical modulations in the immune reactivity of subunits A and B by their putative biochemical modifications. This response asymmetrically modulates H(+)-transport and ATP hydrolysis, exhibiting distinct properties for the activated versus non-activated enzymes.
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Affiliation(s)
- Camila C. Ribeiro
- Laboratório de Fisiologia e Bioquímica de Microrganismos, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
- Laboratório de Biologia Celular e Tecidual, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
| | - Renan M. Monteiro
- Laboratório de Fisiologia e Bioquímica de Microrganismos, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
| | - Flavia P. Freitas
- Laboratório de Fisiologia e Bioquímica de Microrganismos, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
| | - Claudio Retamal
- Laboratório de Biologia Celular e Tecidual, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
| | - Layz R. S. Teixeira
- Laboratório de Fisiologia e Bioquímica de Microrganismos, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
| | - Livia M. Palma
- Laboratório de Fisiologia e Bioquímica de Microrganismos, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
| | - Flavia E. Silva
- Laboratório de Fisiologia e Bioquímica de Microrganismos, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
| | - Arnoldo R. Façanha
- Laboratório de Biologia Celular e Tecidual, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
| | - Anna L. Okorokova-Façanha
- Laboratório de Fisiologia e Bioquímica de Microrganismos, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
| | - Lev A. Okorokov
- Laboratório de Fisiologia e Bioquímica de Microrganismos, Centro de Biociência e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brasil
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31
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Benlekbir S, Bueler SA, Rubinstein JL. Structure of the vacuolar-type ATPase from Saccharomyces cerevisiae at 11-Å resolution. Nat Struct Mol Biol 2012; 19:1356-62. [PMID: 23142977 DOI: 10.1038/nsmb.2422] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 09/21/2012] [Indexed: 11/09/2022]
Abstract
Vacuolar-type ATPases (V-type ATPases) in eukaryotic cells are large membrane protein complexes that acidify various intracellular compartments. The enzymes are regulated by dissociation of the V(1) and V(O) regions of the complex. Here we present the structure of the Saccharomyces cerevisiae V-type ATPase at 11-Å resolution by cryo-EM of protein particles in ice. The structure explains many cross-linking and protein interaction studies. Docking of crystal structures suggests that inhibition of ATPase activity by the dissociated V(1) region involves rearrangement of the N- and C-terminal domains of subunit H and also suggests how this inhibition is triggered upon dissociation. We provide support for this model by demonstrating that mutation of subunit H to increase the rigidity of the linker between its two domains decreases its ability to inhibit ATPase activity.
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Affiliation(s)
- Samir Benlekbir
- Molecular Structure and Function Program, The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
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32
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Parsons LS, Wilkens S. Probing subunit-subunit interactions in the yeast vacuolar ATPase by peptide arrays. PLoS One 2012; 7:e46960. [PMID: 23071676 PMCID: PMC3470569 DOI: 10.1371/journal.pone.0046960] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 09/07/2012] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Vacuolar (H(+))-ATPase (V-ATPase; V(1)V(o)-ATPase) is a large multisubunit enzyme complex found in the endomembrane system of all eukaryotic cells where its proton pumping action serves to acidify subcellular organelles. In the plasma membrane of certain specialized tissues, V-ATPase functions to pump protons from the cytoplasm into the extracellular space. The activity of the V-ATPase is regulated by a reversible dissociation mechanism that involves breaking and re-forming of protein-protein interactions in the V(1)-ATPase - V(o)-proton channel interface. The mechanism responsible for regulated V-ATPase dissociation is poorly understood, largely due to a lack of detailed knowledge of the molecular interactions that are responsible for the structural and functional link between the soluble ATPase and membrane bound proton channel domains. METHODOLOGY/PRINCIPAL FINDINGS To gain insight into where some of the stator subunits of the V-ATPase associate with each other, we have developed peptide arrays from the primary sequences of V-ATPase subunits. By probing the peptide arrays with individually expressed V-ATPase subunits, we have identified several key interactions involving stator subunits E, G, C, H and the N-terminal domain of the membrane bound a subunit. CONCLUSIONS The subunit-peptide interactions identified from the peptide arrays complement low resolution structural models of the eukaryotic vacuolar ATPase obtained from transmission electron microscopy. The subunit-subunit interaction data are discussed in context of our current model of reversible enzyme dissociation.
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Affiliation(s)
- Lee S. Parsons
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, United States of America
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, United States of America
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33
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Uner NE, Nishikawa Y, Okuno D, Nakano M, Yokoyama K, Noji H. Single-molecule analysis of inhibitory pausing states of V1-ATPase. J Biol Chem 2012; 287:28327-35. [PMID: 22736762 DOI: 10.1074/jbc.m112.381194] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
V(1)-ATPase, the hydrophilic V-ATPase domain, is a rotary motor fueled by ATP hydrolysis. Here, we found that Thermus thermophilus V(1)-ATPase shows two types of inhibitory pauses interrupting continuous rotation: a short pause (SP, 4.2 s) that occurred frequently during rotation, and a long inhibitory pause (LP, >30 min) that terminated all active rotations. Both pauses occurred at the same angle for ATP binding and hydrolysis. Kinetic analysis revealed that the time constants of inactivation into and activation from the SP were too short to represent biochemically predicted ADP inhibition, suggesting that SP is a newly identified inhibitory state of V(1)-ATPase. The time constant of inactivation into LP was 17 min, consistent with one of the two time constants governing the inactivation process observed in bulk ATPase assay. When forcibly rotated in the forward direction, V(1) in LP resumed active rotation. Solution ADP suppressed the probability of mechanical activation, suggesting that mechanical rotation enhanced inhibitory ADP release. These features were highly consistent with mechanical activation of ADP-inhibited F(1), suggesting that LP represents the ADP-inhibited state of V(1)-ATPase. Mechanical activation largely depended on the direction and angular displacement of forced rotation, implying that V(1)-ATPase rotation modulates the off rate of ADP.
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Affiliation(s)
- Naciye Esma Uner
- Department of Biotechnology, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
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34
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Qin A, Cheng TS, Pavlos NJ, Lin Z, Dai KR, Zheng MH. V-ATPases in osteoclasts: structure, function and potential inhibitors of bone resorption. Int J Biochem Cell Biol 2012; 44:1422-35. [PMID: 22652318 DOI: 10.1016/j.biocel.2012.05.014] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Revised: 05/18/2012] [Accepted: 05/18/2012] [Indexed: 01/06/2023]
Abstract
The vacuolar-type H(+)-ATPase (V-ATPase) proton pump is a macromolecular complex composed of at least 14 subunits organized into two functional domains, V(1) and V(0). The complex is located on the ruffled border plasma membrane of bone-resorbing osteoclasts, mediating extracellular acidification for bone demineralization during bone resorption. Genetic studies from mice to man implicate a critical role for V-ATPase subunits in osteoclast-related diseases including osteopetrosis and osteoporosis. Thus, the V-ATPase complex is a potential molecular target for the development of novel anti-resorptive agents useful for the treatment of osteolytic diseases. Here, we review the current structure and function of V-ATPase subunits, emphasizing their exquisite roles in osteoclastic function. In addition, we compare several distinct classes of V-ATPase inhibitors with specific inhibitory effects on osteoclasts. Understanding the structure-function relationship of the osteoclast V-ATPase may lead to the development of osteoclast-specific V-ATPase inhibitors that may serve as alternative therapies for the treatment of osteolytic diseases.
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Affiliation(s)
- A Qin
- Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Crawley, Australia.
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35
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Baumann O, Walz B. The blowfly salivary gland - a model system for analyzing the regulation of plasma membrane V-ATPase. JOURNAL OF INSECT PHYSIOLOGY 2012; 58:450-458. [PMID: 22133312 DOI: 10.1016/j.jinsphys.2011.11.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 11/17/2011] [Accepted: 11/18/2011] [Indexed: 05/31/2023]
Abstract
Vacuolar H(+)-ATPases (V-ATPases) are heteromultimeric proteins that use the energy of ATP hydrolysis for the electrogenic transport of protons across membranes. They are common to all eukaryotic cells and are located in the plasma membrane or in membranes of acid organelles. In many insect epithelia, V-ATPase molecules reside in large numbers in the apical plasma membrane and create an electrochemical proton gradient that is used for the acidification or alkalinization of the extracellular space, the secretion or reabsorption of ions and fluids, the import of nutrients, and diverse other cellular activities. Here, we summarize our results on the functions and regulation of V-ATPase in the tubular salivary gland of the blowfly Calliphora vicina. In this gland, V-ATPase activity energizes the secretion of a KCl-rich saliva in response to the neurohormone serotonin (5-HT). Because of particular morphological and physiological features, the blowfly salivary glands are a superior and exemplary system for the analysis of the intracellular signaling pathways and mechanisms that modulate V-ATPase activity and solute transport in an insect epithelium.
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Affiliation(s)
- Otto Baumann
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany.
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36
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Kane PM. Targeting reversible disassembly as a mechanism of controlling V-ATPase activity. Curr Protein Pept Sci 2012; 13:117-23. [PMID: 22044153 PMCID: PMC3536023 DOI: 10.2174/138920312800493142] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 08/05/2011] [Accepted: 08/06/2011] [Indexed: 11/22/2022]
Abstract
Vacuolar proton-translocating ATPases (V-ATPases) are highly conserved proton pumps consisting of a peripheral membrane subcomplex called V1, which contains the sites of ATP hydrolysis, attached to an integral membrane subcomplex called Vo, which encompasses the proton pore. V-ATPase regulation by reversible dissociation, characterized by release of assembled V1 sectors into the cytosol and inhibition of both ATPase and proton transport activities, was first identified in tobacco hornworm and yeast. It has since become clear that modulation of V-ATPase assembly level is also a regulatory mechanism in mammalian cells. In this review, the implications of reversible disassembly for V-ATPase structure are discussed, along with insights into underlying subunit-subunit interactions provided by recent structural work. Although initial experiments focused on glucose deprivation as a trigger for disassembly, it is now clear that V-ATPase assembly can be regulated by other extracellular conditions. Consistent with a complex, integrated response to extracellular signals, a number of different regulatory proteins, including RAVE/rabconnectin, aldolase and other glycolytic enzymes, and protein kinase A have been suggested to control V-ATPase assembly and disassembly. It is likely that multiple signaling pathways dictate the ultimate level of assembly and activity. Tissue-specific V-ATPase inhibition is a potential therapy for osteoporosis and cancer; the possibility of exploiting reversible disassembly in design of novel V-ATPase inhibitors is discussed.
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Affiliation(s)
- Patricia M Kane
- Dept. of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 East Adams St., Syracuse, NY 13210, USA.
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37
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Oot RA, Wilkens S. Subunit interactions at the V1-Vo interface in yeast vacuolar ATPase. J Biol Chem 2012; 287:13396-406. [PMID: 22367203 DOI: 10.1074/jbc.m112.343962] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Eukaryotic vacuolar ATPase (V-ATPase) is regulated by a reversible dissociation mechanism that involves breaking and reforming of protein-protein interactions at the interface of the V(1)-ATPase and V(o)-proton channel domains. We found previously that the head domain of the single copy C subunit (C(head)) binds one subunit EG heterodimer with high affinity (Oot, R.A. and Wilkens, S. (2010) J. Biol. Chem. 285, 24654-24664). Here we generated a water-soluble construct of the N-terminal domain of the V(o) "a" subunit composed of amino acid residues 104-372 (a(NT(104-372))). Analytical gel filtration chromatography and sedimentation velocity analysis revealed that a(NT(104-372)) undergoes reversible dimerization in a concentration-dependent manner. A low-resolution molecular envelope was calculated for the a(NT(104-372)) dimer using small angle x-ray scattering data. Isothermal titration calorimetry experiments revealed that a(NT(104-372)) binds the C(foot) and EG heterodimer with dissociation constants of 22 and 33 μM, respectively. We speculate that the spatial closeness of the a(NT), C(foot), and EG binding sites in the intact V-ATPase results in a high-avidity interaction that is able to resist the torque of rotational catalysis, and that reversible enzyme dissociation is initiated by breaking either the a(NT(104-372))-C(foot) or a(NT(104-372))-EG interaction by an as-yet unknown signaling mechanism.
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Affiliation(s)
- Rebecca A Oot
- Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210, USA
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38
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Regulation of vacuolar H+-ATPase activity by the Cdc42 effector Ste20 in Saccharomyces cerevisiae. EUKARYOTIC CELL 2012; 11:442-51. [PMID: 22327006 DOI: 10.1128/ec.05286-11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the budding yeast Saccharomyces cerevisiae, the Cdc42 effector Ste20 plays a crucial role in the regulation of filamentous growth, a response to nutrient limitation. Using the split-ubiquitin technique, we found that Ste20 forms a complex with Vma13, an important regulatory subunit of vacuolar H(+)-ATPase (V-ATPase). This protein-protein interaction was confirmed by a pulldown assay and coimmunoprecipitation. We also demonstrate that Ste20 associates with vacuolar membranes and that Ste20 stimulates V-ATPase activity in isolated vacuolar membranes. This activation requires Ste20 kinase activity and does not depend on increased assembly of the V1 and V0 sectors of the V-ATPase, which is a major regulatory mechanism. Furthermore, loss of V-ATPase activity leads to a strong increase in invasive growth, possibly because these cells fail to store and mobilize nutrients efficiently in the vacuole in the absence of the vacuolar proton gradient. In contrast to the wild type, which grows in rather small, isolated colonies on solid medium during filamentation, hyperinvasive vma mutants form much bigger aggregates in which a large number of cells are tightly clustered together. Genetic data suggest that Ste20 and the protein kinase A catalytic subunit Tpk2 are both activated in the vma13Δ strain. We propose that during filamentous growth, Ste20 stimulates V-ATPase activity. This would sustain nutrient mobilization from vacuolar stores, which is beneficial for filamentous growth.
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39
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Srinivasan S, Vyas NK, Baker ML, Quiocho FA. Crystal structure of the cytoplasmic N-terminal domain of subunit I, a homolog of subunit a, of V-ATPase. J Mol Biol 2011; 412:14-21. [PMID: 21787787 DOI: 10.1016/j.jmb.2011.07.014] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 07/08/2011] [Accepted: 07/12/2011] [Indexed: 11/17/2022]
Abstract
Subunit "a" is associated with the membrane-bound (V(O)) complex of eukaryotic vacuolar H(+)-ATPase acidification machinery. It has also been shown recently to be involved in diverse membrane fusion/secretory functions independent of acidification. Here, we report the crystal structure of the N-terminal cytosolic domain from the Meiothermus ruber subunit "I" homolog of subunit a. The structure is composed of a curved long central α-helix bundle capped on both ends by two lobes with similar α/β architecture. Based on the structure, a reasonable model of its eukaryotic subunit a counterpart was obtained. The crystal structure and model fit well into reconstructions from electron microscopy of prokaryotic and eukaryotic vacuolar H(+)-ATPases, respectively, clarifying their orientations and interactions and revealing features that could enable subunit a to play a role in membrane fusion/secretion.
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Affiliation(s)
- Sankaranarayanan Srinivasan
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
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40
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Abstract
AbstractThe rotary ATPase family of membrane protein complexes may have only three members, but each one plays a fundamental role in biological energy conversion. The F1Fo-ATPase (F-ATPase) couples ATP synthesis to the electrochemical membrane potential in bacteria, mitochondria and chloroplasts, while the vacuolar H+-ATPase (V-ATPase) operates as an ATP-driven proton pump in eukaryotic membranes. In different species of archaea and bacteria, the A1Ao-ATPase (A-ATPase) can function as either an ATP synthase or an ion pump. All three of these multi-subunit complexes are rotary molecular motors, sharing a fundamentally similar mechanism in which rotational movement drives the energy conversion process. By analogy to macroscopic systems, individual subunits can be assigned to rotor, axle or stator functions. Recently, three-dimensional reconstructions from electron microscopy and single particle image processing have led to a significant step forward in understanding of the overall architecture of all three forms of these complexes and have allowed the organisation of subunits within the rotor and stator parts of the motors to be more clearly mapped out. This review describes the emerging consensus regarding the organisation of the rotor and stator components of V-, A- and F-ATPases, examining core similarities that point to a common evolutionary origin, and highlighting key differences. In particular, it discusses how newly revealed variation in the complexity of the inter-domain connections may impact on the mechanics and regulation of these molecular machines.
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Moore B, Miles AJ, Guerra-Giraldez C, Simpson P, Iwata M, Wallace BA, Matthews SJ, Smith DF, Brown KA. Structural basis of molecular recognition of the Leishmania small hydrophilic endoplasmic reticulum-associated protein (SHERP) at membrane surfaces. J Biol Chem 2010; 286:9246-56. [PMID: 21106528 PMCID: PMC3059043 DOI: 10.1074/jbc.m110.130427] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The 57-residue small hydrophilic endoplasmic reticulum-associated protein (SHERP) shows highly specific, stage-regulated expression in the non-replicative vector-transmitted stages of the kinetoplastid parasite, Leishmania major, the causative agent of human cutaneous leishmaniasis. Previous studies have demonstrated that SHERP localizes as a peripheral membrane protein on the cytosolic face of the endoplasmic reticulum and on outer mitochondrial membranes, whereas its high copy number suggests a critical function in vivo. However, the absence of defined domains or identifiable orthologues, together with lack of a clear phenotype in transgenic parasites lacking SHERP, has limited functional understanding of this protein. Here, we use a combination of biophysical and biochemical methods to demonstrate that SHERP can be induced to adopt a globular fold in the presence of anionic lipids or SDS. Cross-linking and binding studies suggest that SHERP has the potential to form a complex with the vacuolar type H(+)-ATPase. Taken together, these results suggest that SHERP may function in modulating cellular processes related to membrane organization and/or acidification during vector transmission of infective Leishmania.
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Affiliation(s)
- Benjamin Moore
- Division of Cell and Molecular Biology, Centre for Molecular Microbiology and Infection, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom
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Toei M, Saum R, Forgac M. Regulation and isoform function of the V-ATPases. Biochemistry 2010; 49:4715-23. [PMID: 20450191 DOI: 10.1021/bi100397s] [Citation(s) in RCA: 259] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The vacuolar (H(+))-ATPases are ATP-dependent proton pumps that acidify intracellular compartments and, in some cases, transport protons across the plasma membrane of eukaryotic cells. Intracellular V-ATPases play an important role in normal physiological processes such as receptor-mediated endocytosis, intracellular membrane trafficking, pro-hormone processing, protein degradation, and the coupled uptake of small molecules, such as neurotransmitters. They also function in the entry of various pathogenic agents, including many envelope viruses, like influenza virus, and toxins, like anthrax toxin. Plasma membrane V-ATPases function in renal pH homeostasis, bone resorption and sperm maturation, and various disease processes, including renal tubular acidosis, osteopetrosis, and tumor metastasis. V-ATPases are composed of a peripheral V(1) domain containing eight different subunits that is responsible for ATP hydrolysis and an integral V(0) domain containing six different subunits that translocates protons. In mammalian cells, most of the V-ATPase subunits exist in multiple isoforms which are often expressed in a tissue specific manner. Isoforms of one of the V(0) subunits (subunit a) have been shown to possess information that targets the V-ATPase to distinct cellular destinations. Mutations in isoforms of subunit a lead to the human diseases osteopetrosis and renal tubular acidosis. A number of mechanisms are employed to regulate V-ATPase activity in vivo, including reversible dissociation of the V(1) and V(0) domains, control of the tightness of coupling of proton transport and ATP hydrolysis, and selective targeting of V-ATPases to distinct cellular membranes. Isoforms of subunit a are involved in regulation both via the control of coupling and via selective targeting. This review will begin with a brief introduction to the function, structure, and mechanism of the V-ATPases followed by a discussion of the role of V-ATPase subunit isoforms and the mechanisms involved in regulation of V-ATPase activity.
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Affiliation(s)
- Masashi Toei
- Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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Current awareness on yeast. Yeast 2009. [DOI: 10.1002/yea.1626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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