1
|
Expression of plasma membrane calcium ATPases confers Ca 2+/H + exchange in rodent synaptic vesicles. Sci Rep 2019; 9:4289. [PMID: 30862855 PMCID: PMC6414521 DOI: 10.1038/s41598-019-40557-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 02/19/2019] [Indexed: 02/07/2023] Open
Abstract
Ca2+ transport into synaptic vesicles (SVs) at the presynaptic terminals has been proposed to be an important process for regulating presynaptic [Ca2+] during stimulation as well as at rest. However, the molecular identity of the transport system remains elusive. Previous studies have demonstrated that isolated SVs exhibit two distinct Ca2+ transport systems depending on extra-vesicular (cytosolic) pH; one is mediated by a high affinity Ca2+ transporter which is active at neutral pH and the other is mediated by a low affinity Ca2+/H+ antiporter which is maximally active at alkaline pH of 8.5. In addition, synaptic vesicle glycoprotein 2 s (SV2s), a major SV component, have been proposed to contribute to Ca2+ clearance from the presynaptic cytoplasm. Here, we show that at physiological pH, the plasma membrane Ca2+ ATPases (PMCAs) are responsible for both the Ca2+/H+ exchange activity and Ca2+ uptake into SVs. The Ca2+/H+ exchange activity monitored by acidification assay exhibited high affinity for Ca2+ (Km ~ 400 nM) and characteristic divalent cation selectivity for the PMCAs. Both activities were remarkably reduced by PMCA blockers, but not by a blocker of the ATPase that transfers Ca2+ from the cytosol to the lumen of sarcoplasmic endoplasmic reticulum (SERCA) at physiological pH. Furthermore, we rule out the contribution of SV2s, putative Ca2+ transporters on SVs, since both Ca2+/H+ exchange activity and Ca2+ transport were unaffected in isolated vesicles derived from SV2-deficient brains. Finally, using a PMCA1-pHluorin construct that enabled us to monitor cellular distribution and recycling properties in living neurons, we demonstrated that PMCA1-pHluorin localized to intracellular acidic compartments and recycled at presynaptic terminals in an activity-dependent manner. Collectively, our results imply that vesicular PMCAs may play pivotal roles in both presynaptic Ca2+ homeostasis and the modulation of H+ gradient in SVs.
Collapse
|
2
|
Shah VS, Meyerholz DK, Tang XX, Reznikov L, Abou Alaiwa M, Ernst SE, Karp PH, Wohlford-Lenane CL, Heilmann KP, Leidinger MR, Allen PD, Zabner J, McCray PB, Ostedgaard LS, Stoltz DA, Randak CO, Welsh MJ. Airway acidification initiates host defense abnormalities in cystic fibrosis mice. Science 2016; 351:503-7. [PMID: 26823428 DOI: 10.1126/science.aad5589] [Citation(s) in RCA: 228] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cystic fibrosis (CF) is caused by mutations in the gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel. In humans and pigs, the loss of CFTR impairs respiratory host defenses, causing airway infection. But CF mice are spared. We found that in all three species, CFTR secreted bicarbonate into airway surface liquid. In humans and pigs lacking CFTR, unchecked H(+) secretion by the nongastric H(+)/K(+) adenosine triphosphatase (ATP12A) acidified airway surface liquid, which impaired airway host defenses. In contrast, mouse airways expressed little ATP12A and secreted minimal H(+); consequently, airway surface liquid in CF and non-CF mice had similar pH. Inhibiting ATP12A reversed host defense abnormalities in human and pig airways. Conversely, expressing ATP12A in CF mouse airways acidified airway surface liquid, impaired defenses, and increased airway bacteria. These findings help explain why CF mice are protected from infection and nominate ATP12A as a potential therapeutic target for CF.
Collapse
Affiliation(s)
- Viral S Shah
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Department of Molecular Physiology and Biophysics, Pappajohn Biomedical Institute, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - David K Meyerholz
- Department of Pathology, University of Iowa, Iowa City, IA 52242, USA
| | - Xiao Xiao Tang
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Howard Hughes Medical Institute, University of Iowa, Iowa City, IA 52242, USA
| | - Leah Reznikov
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | | | - Sarah E Ernst
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Howard Hughes Medical Institute, University of Iowa, Iowa City, IA 52242, USA
| | - Philip H Karp
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Howard Hughes Medical Institute, University of Iowa, Iowa City, IA 52242, USA
| | | | | | | | - Patrick D Allen
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Joseph Zabner
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Paul B McCray
- Department of Pediatrics University of Iowa, Iowa City, IA 52242, USA. Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA
| | | | - David A Stoltz
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Department of Molecular Physiology and Biophysics, Pappajohn Biomedical Institute, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA. Department of Biomedical Engineering, College of Engineering, University of Iowa, Iowa City, IA 52242, USA
| | | | - Michael J Welsh
- Department of Medicine, University of Iowa, Iowa City, IA 52242, USA. Department of Molecular Physiology and Biophysics, Pappajohn Biomedical Institute, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA. Howard Hughes Medical Institute, University of Iowa, Iowa City, IA 52242, USA
| |
Collapse
|
3
|
Morel N, Poëa-Guyon S. The membrane domain of vacuolar H(+)ATPase: a crucial player in neurotransmitter exocytotic release. Cell Mol Life Sci 2015; 72:2561-73. [PMID: 25795337 PMCID: PMC11113229 DOI: 10.1007/s00018-015-1886-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 03/10/2015] [Accepted: 03/12/2015] [Indexed: 12/31/2022]
Abstract
V-ATPases are multimeric enzymes made of two sectors, a V1 catalytic domain and a V0 membrane domain. They accumulate protons in various intracellular organelles. Acidification of synaptic vesicles by V-ATPase energizes the accumulation of neurotransmitters in these storage organelles and is therefore required for efficient synaptic transmission. In addition to this well-accepted role, functional studies have unraveled additional hidden roles of V0 in neurotransmitter exocytosis that are independent of the transport of protons. V0 interacts with SNAREs and calmodulin, and perturbing these interactions affects neurotransmitter release. Here, we discuss these data in relation with previous results obtained in reconstituted membranes and on yeast vacuole fusion. We propose that V0 could be a sensor of intra-vesicular pH that controls the exocytotic machinery, probably regulating SNARE complex assembly during the synaptic vesicle priming step, and that, during the membrane fusion step, V0 might favor lipid mixing and fusion pore stability.
Collapse
Affiliation(s)
- Nicolas Morel
- Centre de Neurosciences Paris-Sud, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8195 and Université Paris-Sud, 91405, Orsay, France,
| | | |
Collapse
|
4
|
Rangaraju V, Calloway N, Ryan TA. Activity-driven local ATP synthesis is required for synaptic function. Cell 2014; 156:825-35. [PMID: 24529383 DOI: 10.1016/j.cell.2013.12.042] [Citation(s) in RCA: 513] [Impact Index Per Article: 51.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 11/01/2013] [Accepted: 12/31/2013] [Indexed: 01/20/2023]
Abstract
Cognitive function is tightly related to metabolic state, but the locus of this control is not well understood. Synapses are thought to present large ATP demands; however, it is unclear how fuel availability and electrical activity impact synaptic ATP levels and how ATP availability controls synaptic function. We developed a quantitative genetically encoded optical reporter of presynaptic ATP, Syn-ATP, and find that electrical activity imposes large metabolic demands that are met via activity-driven control of both glycolysis and mitochondrial function. We discovered that the primary source of activity-driven metabolic demand is the synaptic vesicle cycle. In metabolically intact synapses, activity-driven ATP synthesis is well matched to the energetic needs of synaptic function, which, at steady state, results in ∼10(6) free ATPs per nerve terminal. Despite this large reservoir of ATP, we find that several key aspects of presynaptic function are severely impaired following even brief interruptions in activity-stimulated ATP synthesis.
Collapse
Affiliation(s)
- Vidhya Rangaraju
- Rockefeller/Sloan-Kettering/Weill Cornell Tri-Institutional Training Program in Chemical Biology, New York, NY 10065, USA; Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Nathaniel Calloway
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Timothy A Ryan
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA.
| |
Collapse
|
5
|
Poëa-Guyon S, Ammar MR, Erard M, Amar M, Moreau AW, Fossier P, Gleize V, Vitale N, Morel N. The V-ATPase membrane domain is a sensor of granular pH that controls the exocytotic machinery. ACTA ACUST UNITED AC 2013; 203:283-98. [PMID: 24165939 PMCID: PMC3812966 DOI: 10.1083/jcb.201303104] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Several studies have suggested that the V0 domain of the vacuolar-type H(+)-adenosine triphosphatase (V-ATPase) is directly implicated in secretory vesicle exocytosis through a role in membrane fusion. We report in this paper that there was a rapid decrease in neurotransmitter release after acute photoinactivation of the V0 a1-I subunit in neuronal pairs. Likewise, inactivation of the V0 a1-I subunit in chromaffin cells resulted in a decreased frequency and prolonged kinetics of amperometric spikes induced by depolarization, with shortening of the fusion pore open time. Dissipation of the granular pH gradient was associated with an inhibition of exocytosis and correlated with the V1-V0 association status in secretory granules. We thus conclude that V0 serves as a sensor of intragranular pH that controls exocytosis and synaptic transmission via the reversible dissociation of V1 at acidic pH. Hence, the V-ATPase membrane domain would allow the exocytotic machinery to discriminate fully loaded and acidified vesicles from vesicles undergoing neurotransmitter reloading.
Collapse
Affiliation(s)
- Sandrine Poëa-Guyon
- Centre de Neurosciences Paris-Sud, Centre National de la Recherche Scientifique Unité Mixte de Recherche 8195 and Université Paris-Sud, F-91405 Orsay, France
| | | | | | | | | | | | | | | | | |
Collapse
|
6
|
Lee JS, Agrawal S, von Turkovich M, Taatjes DJ, Walz DA, Jena BP. Water channels in platelet volume regulation. J Cell Mol Med 2012; 16:945-9. [PMID: 21692982 PMCID: PMC3822864 DOI: 10.1111/j.1582-4934.2011.01362.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The regulation of platelet volume significantly affects its function. Because water is the major molecule in cells and its active transport via water channels called aquaporins (AQPs) have been implicated in cellular and organelle volume regulation, the presence of water channels in platelets and their potential role in platelet volume regulation was investigated. G-protein-mediated AQP regulation in secretory vesicle swelling has previously been reported in neurons and in pancreatic acinar cells. Mercuric chloride has been demonstrated to inhibit most AQPs except AQP6, which is stimulated by the compound. Exposure of platelets to HgCl(2)-induced swelling in a dose-dependent manner, suggesting the presence of AQP6 in platelets. Immunoblot analysis of platelet protein confirmed the presence of AQP6, and also of G(αo), G(αi-1) and G(αi-3) proteins. Results from this study demonstrate for the first time that in platelets AQP6 is involved in cell volume regulation via a G-protein-mediated pathway.
Collapse
Affiliation(s)
- Jin-Sook Lee
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | | | | | | | | | | |
Collapse
|
7
|
Levano K, Punia V, Raghunath M, Debata PR, Curcio GM, Mogha A, Purkayastha S, McCloskey D, Fata J, Banerjee P. Atp8a1 deficiency is associated with phosphatidylserine externalization in hippocampus and delayed hippocampus-dependent learning. J Neurochem 2011; 120:302-13. [PMID: 22007859 DOI: 10.1111/j.1471-4159.2011.07543.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The molecule responsible for the enzyme activity plasma membrane (PM) aminophospholipid translocase (APLT), which catalyzes phosphatidylserine (PS) translocation from the outer to the inner leaflet of the plasma membrane, is unknown in mammals. A Caenorhabditis elegans study has shown that ablation of transbilayer amphipath transporter-1 (TAT-1), which is an ortholog of a mammalian P-type ATPase, Atp8a1, causes PS externalization in the germ cells. We demonstrate here that the hippocampal cells of the dentate gyrus, and Cornu Ammonis (CA1, CA3) in mice lacking Atp8a1 exhibit a dramatic increase in PS externalization. Although their hippocampi showed no abnormal morphology or heightened apoptosis, these mice displayed increased activity and a marked deficiency in hippocampus-dependent learning, but no hyper-anxiety. Such observations indicate that Atp8a1 plays a crucial role in PM-APLT activity in the neuronal cells. In corroboration, ectopic expression of Atp8a1 but not its close homolog, Atp8a2, caused an increase in the population (V(max) ) of PM-APLT without any change in its signature parameter K(m) in the neuronal N18 cells. Conversely, expression of a P-type phosphorylation-site mutant of Atp8a1 (Atp8a1*) caused a decrease in V(max) of PM-APLT without significantly altering its K(m) . The Atp8a1*-expressing N18 cells also exhibited PS externalization without apoptosis. Together, our data strongly indicate that Atp8a1 plays a central role in the PM-APLT activity of some mammalian cells, such as the neuronal N18 and hippocampal cells.
Collapse
Affiliation(s)
- Kelly Levano
- CUNY Doctoral Program in Biochemistry, City University of New York at the College of Staten Island, Staten Island, New York, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Molecular mechanisms of endolysosomal Ca2+ signalling in health and disease. Biochem J 2011; 439:349-74. [PMID: 21992097 DOI: 10.1042/bj20110949] [Citation(s) in RCA: 295] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Endosomes, lysosomes and lysosome-related organelles are emerging as important Ca2+ storage cellular compartments with a central role in intracellular Ca2+ signalling. Endocytosis at the plasma membrane forms endosomal vesicles which mature to late endosomes and culminate in lysosomal biogenesis. During this process, acquisition of different ion channels and transporters progressively changes the endolysosomal luminal ionic environment (e.g. pH and Ca2+) to regulate enzyme activities, membrane fusion/fission and organellar ion fluxes, and defects in these can result in disease. In the present review we focus on the physiology of the inter-related transport mechanisms of Ca2+ and H+ across endolysosomal membranes. In particular, we discuss the role of the Ca2+-mobilizing messenger NAADP (nicotinic acid adenine dinucleotide phosphate) as a major regulator of Ca2+ release from endolysosomes, and the recent discovery of an endolysosomal channel family, the TPCs (two-pore channels), as its principal intracellular targets. Recent molecular studies of endolysosomal Ca2+ physiology and its regulation by NAADP-gated TPCs are providing exciting new insights into the mechanisms of Ca2+-signal initiation that control a wide range of cellular processes and play a role in disease. These developments underscore a new central role for the endolysosomal system in cellular Ca2+ regulation and signalling.
Collapse
|
9
|
Lee JS, Cho WJ, Shin L, Jena BP. Involvement of cholesterol in synaptic vesicle swelling. Exp Biol Med (Maywood) 2010; 235:470-7. [PMID: 20407079 DOI: 10.1258/ebm.2010.009259] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Studies demonstrate that cholesterol plays a critical role in the regulation of neurotransmitter release and that secretory vesicle swelling is a requirement for the regulated expulsion of intravesicular contents during cell secretion. In view of this, the involvement of cholesterol in synaptic vesicle swelling was hypothesized and tested in the present study, using isolated synaptic vesicles from rat brain and the determination of their swelling competency in the presence and absence of cholesterol. The involvement of the water channel aquaporin-6 (AQP-6) and proton pump vH(+)-ATPase in GTP-G(alpha o)-mediated synaptic vesicle swelling has been reported previously. Mastoparan, the amphiphilic tetradecapeptide from wasp venom, known to activate the GTPase activity of G(alpha o/i) proteins, stimulates synaptic vesicle swelling in the presence of GTP. In the current study, using nanometer-scale precision measurements of isolated synaptic vesicles, we report for the first time that depletion of cholesterol from synaptic vesicle membrane results in a significant loss of GTP-mastoparan-stimulable synaptic vesicle swelling. In contrast, incorporation of cholesterol into the synaptic vesicle membrane potentiates GTP-mastoparan-stimulable vesicle swelling. Our study further demonstrates that this effect of cholesterol is due, in part, to its involvement in the interactions between AQP-6, vH(+)-ATPase and the GTP-binding G(alpha o) protein at the synaptic vesicle membrane.
Collapse
Affiliation(s)
- Jin-Sook Lee
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | | | | | | |
Collapse
|
10
|
Jena BP. Functional organization of the porosome complex and associated structures facilitating cellular secretion. Physiology (Bethesda) 2010; 24:367-76. [PMID: 19996367 DOI: 10.1152/physiol.00021.2009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Porosomes, the universal secretory machinery at the cell plasma membrane, are cup-shaped supramolecular lipoprotein structures, where membrane-bound vesicles transiently dock and fuse to release intravesicular contents during cell secretion. In this review, the discovery of the porosome and its structure, dynamics, composition, and functional reconstitution are outlined. Furthermore, the architecture of porosome-like structures such as the "canaliculi system" in human platelets and various associated structures such as the T-bars at the Drosophila synapse or the "beams," "ribs," and "pegs" at the frog neuromuscular junction, each organized to facilitate a certain specialized secretory activity, are briefly discussed.
Collapse
Affiliation(s)
- Bhanu P Jena
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA.
| |
Collapse
|
11
|
Shin L, Basi N, Jeremic A, Lee JS, Cho WJ, Chen Z, Abu-Hamdah R, Oupicky D, Jena BP. Involvement of vH(+)-ATPase in synaptic vesicle swelling. J Neurosci Res 2010; 88:95-101. [PMID: 19610106 DOI: 10.1002/jnr.22180] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Secretory vesicle swelling is central to cell secretion, but the underlying mechanism of vesicle swelling, particularly synaptic vesicles, is not completely understood. The G(alphai3)-PLA2-mediated involvement of water channel AQP-1 in the regulation of secretory vesicle swelling in exocrine pancreas and the G(alphao)-mediated AQP-6 involvement in synaptic vesicle swelling in neurons have previously been reported. Furthermore, the role of vH(+)-ATPase in neurotransmitter transport into synaptic vesicles has also been shown. Using nanometer-scale precision measurements of isolated synaptic vesicles, the present study reports for the first time the involvement of vH(+)-ATPase in GTP-G(alphao)-mediated synaptic vesicle swelling. Results from this study demonstrate that the GTP-G(alphao)-mediated vesicle swelling is vH(+)-ATPase dependent and pH sensitive. Zeta potential measurements of isolated synaptic vesicles further demonstrate a bafilomycin-sensitive vesicle acidification, following the GTP-G(alphao)-induced swelling stimulus. Water channels are bidirectional and the vH(+)-ATPase inhibitor bafilomycin decreases both the volume of isolated synaptic vesicles and GTP-mastoparan stimulated swelling, suggesting that vH(+)-ATPase is upstream of AQP-6, in the pathway leading from G(alphao)-stimulated swelling of synaptic vesicles. Vesicle acidification is therefore a prerequisite for AQP-6-mediated gating of water into synaptic vesicles.
Collapse
Affiliation(s)
- Leah Shin
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Stöckl M, Fischer P, Wanker E, Herrmann A. Alpha-synuclein selectively binds to anionic phospholipids embedded in liquid-disordered domains. J Mol Biol 2007; 375:1394-404. [PMID: 18082181 DOI: 10.1016/j.jmb.2007.11.051] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Revised: 10/15/2007] [Accepted: 11/15/2007] [Indexed: 11/27/2022]
Abstract
Previous studies indicate that binding of alpha-synuclein to membranes is critical for its physiological function and the development of Parkinson's disease (PD). Here, we have investigated the association of fluorescence-labeled alpha-synuclein variants with different types of giant unilamellar vesicles using confocal microscopy. We found that alpha-synuclein binds with high affinity to anionic phospholipids, when they are embedded in a liquid-disordered as opposed to a liquid-ordered environment. This indicates that not only electrostatic forces but also lipid packing and hydrophobic interactions are critical for the association of alpha-synuclein with membranes in vitro. When compared to wild-type alpha-synuclein, the disease-causing alpha-synuclein variant A30P bound less efficiently to anionic phospholipids, while the variant E46K showed enhanced binding. This suggests that the natural association of alpha-synuclein with membranes is altered in the inherited forms of Parkinson's disease.
Collapse
Affiliation(s)
- Martin Stöckl
- Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, Institut für Biologie/Biophysik, Invalidenstr. 43, D-10115 Berlin, Germany
| | | | | | | |
Collapse
|
13
|
Poëa-Guyon S, Amar M, Fossier P, Morel N. Alternative splicing controls neuronal expression of v-ATPase subunit a1 and sorting to nerve terminals. J Biol Chem 2006; 281:17164-17172. [PMID: 16621796 DOI: 10.1074/jbc.m600927200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vacuolar proton ATPase accumulates protons inside various intracellular organelles such as synaptic vesicles; its membrane domain V0 could also be involved in membrane fusion. These different functions could require vacuolar proton ATPases possessing different V0 subunit a isoforms. In vertebrates, four genes encode isoforms a1-a4, and a1 variants are also generated by alternative splicing. We identified a novel a1 splice variant a1-IV and showed that the two a1 variants containing exon C are specifically expressed in neurons. Single neurons coexpress a2, a1-I, and a1-IV, and these subunit a isoforms are targeted to different membrane compartments. Recombinant a2 was accumulated in the trans-Golgi network, and a1-I was concentrated in axonal varicosities, whereas a1-IV was sorted to both distal dendrites and axons. Our results indicate that alternative splicing of exon N controls differential sorting of a1 variants to nerve terminals or distal dendrites, whereas exon C regulates their neuronal expression.
Collapse
Affiliation(s)
- Sandrine Poëa-Guyon
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS UPR9040, 91198 Gif sur Yvette, France
| | - Muriel Amar
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS UPR9040, 91198 Gif sur Yvette, France
| | - Philippe Fossier
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS UPR9040, 91198 Gif sur Yvette, France
| | - Nicolas Morel
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS UPR9040, 91198 Gif sur Yvette, France.
| |
Collapse
|
14
|
Camacho M, Machado JD, Montesinos MS, Criado M, Borges R. Intragranular pH rapidly modulates exocytosis in adrenal chromaffin cells. J Neurochem 2005; 96:324-34. [PMID: 16336635 DOI: 10.1111/j.1471-4159.2005.03526.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several drugs produce rapid changes in the kinetics of exocytosis of catecholamines, as measured at the single event level with amperometry. This study is intended to unveil whether the mechanism(s) responsible for these effects involve changes in the intravesicular pH. Cell incubation with bafilomycin A1, a blocker of the vesicular proton pump, caused both a deceleration in the kinetics of exocytosis and a reduction in the catecholamine content of vesicle. These effects were also observed upon reduction of proton gradient by nigericin or NH4Cl. pH measurements using fluorescent probes (acridine orange, quinacrine or enhanced green fluorescent protein-synaptobrevin) showed a strong correlation between vesicular pH and the kinetics of exocytosis. Hence, all maneuvers tested that decelerated exocytosis also alkalinized secretory vesicles and vice versa. On the other hand, calcium entry caused a transient acidification of granules. We therefore propose that the regulation of vesicular pH is, at least partially, a necessary step in the modulation of the kinetics of exocytosis and quantal size operated by some cell signals.
Collapse
Affiliation(s)
- Marcial Camacho
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, Tenerife, Spain
| | | | | | | | | |
Collapse
|
15
|
Morel N, Dedieu JC, Philippe JM. Specific sorting of the a1 isoform of the V-H+ATPase a subunit to nerve terminals where it associates with both synaptic vesicles and the presynaptic plasma membrane. J Cell Sci 2004; 116:4751-62. [PMID: 14600261 DOI: 10.1242/jcs.00791] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vacuolar H+ATPase (V-ATPase) accumulates protons inside various intracellular organelles, generating the electrochemical proton gradient required for many vital cellular processes. V-ATPase is a complex enzyme with many subunits that are organized into two domains. The membrane domain that translocates protons contains a proteolipid oligomer of several c subunits and a 100 kDa a subunit. Several a-subunit isoforms have been described that are important for tissue specificity and targeting to different membrane compartments, and could also result in the generation of V-ATPases with different functional properties. In the present report, we have cloned the Torpedo marmorata a1 isoform. This isoform was found to be addressed specifically to nerve endings, whereas VATPases in the neuron cell bodies contain a different a-subunit isoform. In nerve terminals, the V-ATPase membrane domain is present not only in synaptic vesicles but also in the presynaptic plasma membrane, where its density could reach 200 molecules microm(-2). This V-ATPase interacts with VAMP-2 and with the SNARE complexes involved in synaptic vesicle docking and exocytosis.
Collapse
Affiliation(s)
- Nicolas Morel
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS, 91198 Gif sur Yvette, France.
| | | | | |
Collapse
|
16
|
Van der Kloot W. Loading and recycling of synaptic vesicles in the Torpedo electric organ and the vertebrate neuromuscular junction. Prog Neurobiol 2003; 71:269-303. [PMID: 14698765 DOI: 10.1016/j.pneurobio.2003.10.003] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In vertebrate motor nerve terminals and in the electromotor nerve terminals of Torpedo there are two major pools of synaptic vesicles: readily releasable and reserve. The electromotor terminals differ in that the reserve vesicles are twice the diameter of the readily releasable vesicles. The vesicles contain high concentrations of ACh and ATP. Part of the ACh is brought into the vesicle by the vesicular ACh transporter, VAChT, which exchanges two protons for each ACh, but a fraction of the ACh seems to be accumulated by different, unexplored mechanisms. Most of the vesicles in the terminals do not exchange ACh or ATP with the axoplasm, although ACh and ATP are free in the vesicle interior. The VAChT is controlled by a multifaceted regulatory complex, which includes the proteoglycans that characterize the cholinergic vesicles. The drug (-)-vesamicol binds to a site on the complex and blocks ACh exchange. Only 10-20% of the vesicles are in the readily releasable pool, which therefore is turned over fairly rapidly by spontaneous quantal release. The turnover can be followed by the incorporation of false transmitters into the recycling vesicles, and by the rate of uptake of FM dyes, which have some selectivity for the two recycling pathways. The amount of ACh loaded into recycling vesicles in the readily releasable pool decreases during stimulation. The ACh content of the vesicles can be varied over eight-fold range without changing vesicle size.
Collapse
Affiliation(s)
- William Van der Kloot
- Department of Physiology and Biophysics, SUNY at Stony Brook, 8661 SUNT, Stony Brook, NY 11794-8661, USA.
| |
Collapse
|
17
|
Affiliation(s)
- Peter J Quinn
- Division of Life Sciences, King's College London, 150 Stamford Street, London SE1 9NN, UK
| |
Collapse
|
18
|
Hong SJ. Reduction of quantal size and inhibition of neuromuscular transmission by bafilomycin A. Neuropharmacology 2001; 41:609-17. [PMID: 11587716 DOI: 10.1016/s0028-3908(01)00104-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The energy for uphill transport of neurotransmitters into synaptic vesicles is created by bafilomycin A- and concanamycin A-sensitive vacuolar H(+)-ATPase (V-ATPase). Both blockers (at 0.1-5 microM) depressed twitch tension and induced tetanic fade of mouse diaphragm on stimulation of the phrenic nerve. Axonal impulse conduction and depolarization of motor endplate by exogenous acetylcholine were not inhibited. The IC(50)s for bafilomycin A and concanamycin A were 1.1+/-0.2 and 0.7+/-0.1 microM, respectively. Contractile response evoked by stimulation of diaphragm, muscle resting membrane potential and membrane resistance were not altered. V-ATPase blockers decreased quantal size and shifted the distribution of miniature endplate potentials (mepps) to low amplitude direction. The increase of mepp events in high KCl medium was suppressed slightly. The blockers depressed endplate potentials (epps) with IC(50)s of 0.7+/-0.2 microM (bafilomycin A) and 0.4+/-0.1 microM (concanamycin A). On high frequency stimulation, the coefficient of variance and run-down of epps were increased. The inhibitory effects on mepps and epps were irreversible and augmented by nerve stimulation. The results suggest that inhibition of V-ATPase reduces the acetylcholine content of synaptic vesicles, leading to suppression of neuromuscular transmission.
Collapse
Affiliation(s)
- S J Hong
- Department of Pharmacology, College of Medicine, National Taiwan University, No 1, Sec 1, Jen-Ai Road, ROC, Taipei, Taiwan.
| |
Collapse
|
19
|
Schlegel RA, Williamson P. Phosphatidylserine, a death knell. Cell Death Differ 2001; 8:551-63. [PMID: 11536005 DOI: 10.1038/sj.cdd.4400817] [Citation(s) in RCA: 259] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2000] [Revised: 11/13/2000] [Accepted: 11/27/2000] [Indexed: 11/09/2022] Open
Abstract
Virtually every cell in the body restricts phosphatidylserine (PS) to the inner leaflet of the plasma membrane by energy-dependent transport from the outer to the inner leaflet of the bilayer. Apoptotic cells of all types rapidly randomize the asymmetric distribution, bringing PS to the surface where it serves as a signal for phagocytosis. A myriad of phagocyte receptors have been implicated in the recognition of apoptotic cells, among them a PS receptor, yet few ligands other than PS have been identified on the apoptotic cell surface. Since apoptosis and the associated exposure of PS on the cell surface is probably over 600 million years old, it is not surprising that evolution has appropriated aspects of this process for specialized purposes such as blood coagulation, membrane fusion and erythrocyte differentiation. Failure to efficiently remove apoptotic cells may contribute to inflammatory responses and autoimmune diseases resulting from chronic, inappropriate exposure of PS.
Collapse
Affiliation(s)
- R A Schlegel
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, PA 16802, USA
| | | |
Collapse
|
20
|
Gonçalves PP, Meireles SM, Neves P, Vale MG. Distinction between Ca(2+) pump and Ca(2+)/H(+) antiport activities in synaptic vesicles of sheep brain cortex. Neurochem Int 2000; 37:387-96. [PMID: 10825579 DOI: 10.1016/s0197-0186(00)00009-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Synaptic vesicles, isolated from a sheep brain cortex, accumulate Ca(2+) in a manner that depends on the pH and pCa values. In the presence of 100 microM CaCl(2), most of the Ca(2+) taken up by the vesicles was vanadate-inhibited (86%) at pH 7.4, whereas at pH 8.5, part of the Ca(2+) accumulated (36%) was DeltapH-dependent (bafilomycin and CCCP inhibited) and part was insensitive to those drugs (31%). We also observed that both vanadate-sensitive and bafilomycin-sensitive Ca(2+) accumulations were completely released by the Ca(2+) ionophore, ionomycin, and that these processes work with high (K(0.5)=0.6 microM) and low (K(0.5)=217 microM) affinity for Ca(2+), respectively. The DeltapH-dependent Ca(2+) transport appears to be largely operative at Ca(2+) concentrations (>100 microM) which completely inhibited the vanadate-sensitive Ca(2+) uptake. These Ca(2+) effects on the Ca(2+) accumulation were well correlated with those observed on the vanadate-inhibited Ca(2+)-ATPase and bafilomycin-inhibited H(+)-ATPase, respectively. The Ca(2+)-ATPase activity reached a maximum at about 25 microM (pH 7.4) and sharply declined at higher Ca(2+) concentrations. In contrast, Ca(2+) had a significant stimulatory effect on the H(+)-ATPase between 250 and 500 microM Ca(2+) concentration. Furthermore, we found that DeltapH-sensitive Ca(2+) transport was associated with proton release from the vesicles. About 21% of the maximal proton gradient was dissipated by addition of 607.7 microM CaCl(2) to the reaction medium and, if CaCl(2) was present before the proton accumulation, lower pH gradients were reached. Both vanadate-inhibited and bafilomycin-inhibited systems transported Ca(2+) into the same vesicle pool of our preparation, suggesting that they belong to the same cellular compartment. These results indicate that synaptic vesicles of the sheep brain cortex contain two distinct mechanisms of Ca(2+) transport: a high Ca(2+) affinity, proton gradient-independent Ca(2+) pump that has an optimal activity at pH 7.4, and a low Ca(2+) affinity, proton gradient-dependent Ca(2+)/H(+) antiport that works maximally at pH 8.5.
Collapse
Affiliation(s)
- P P Gonçalves
- Centro de Biologia Celular, Departamento de Biologia, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
| | | | | | | |
Collapse
|
21
|
Chen CY, Ingram MF, Rosal PH, Graham TR. Role for Drs2p, a P-type ATPase and potential aminophospholipid translocase, in yeast late Golgi function. J Cell Biol 1999; 147:1223-36. [PMID: 10601336 PMCID: PMC2168089 DOI: 10.1083/jcb.147.6.1223] [Citation(s) in RCA: 207] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/1999] [Accepted: 11/09/1999] [Indexed: 11/22/2022] Open
Abstract
ADP-ribosylation factor appears to regulate the budding of both COPI and clathrin-coated transport vesicles from Golgi membranes. An arf1Delta synthetic lethal screen identified SWA3/DRS2, which encodes an integral membrane P-type ATPase and potential aminophospholipid translocase (or flippase). The drs2 null allele is also synthetically lethal with clathrin heavy chain (chc1) temperature-sensitive alleles, but not with mutations in COPI subunits or other SEC genes tested. Consistent with these genetic analyses, we found that the drs2Delta mutant exhibits late Golgi defects that may result from a loss of clathrin function at this compartment. These include a defect in the Kex2-dependent processing of pro-alpha-factor and the accumulation of abnormal Golgi cisternae. Moreover, we observed a marked reduction in clathrin-coated vesicles that can be isolated from the drs2Delta cells. Subcellular fractionation and immunofluorescence analysis indicate that Drs2p localizes to late Golgi membranes containing Kex2p. These observations indicate a novel role for a P-type ATPase in late Golgi function and suggest a possible link between membrane asymmetry and clathrin function at the Golgi complex.
Collapse
Affiliation(s)
- Chih-Ying Chen
- Department of Molecular Biology, Vanderbilt University, Nashville, Tennessee 37235
| | - Michael F. Ingram
- Department of Molecular Biology, Vanderbilt University, Nashville, Tennessee 37235
| | - Peter H. Rosal
- Department of Molecular Biology, Vanderbilt University, Nashville, Tennessee 37235
| | - Todd R. Graham
- Department of Molecular Biology, Vanderbilt University, Nashville, Tennessee 37235
| |
Collapse
|
22
|
Gonçalves PP, Meireles SM, Neves P, Vale MG. Synaptic vesicle Ca2+/H+ antiport: dependence on the proton electrochemical gradient. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1999; 71:178-84. [PMID: 10521572 DOI: 10.1016/s0169-328x(99)00183-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Synaptic vesicles isolated from sheep brain cortex accumulate Ca2+ by a mechanism of secondary active transport associated to the H(+)-pump activity. The process can be visualized either by measuring Ca(2+)-induced H+ release or DeltapH-dependent Ca2+ accumulation. We observed that the amount of Ca2+ taken up by the vesicles increases with the magnitude of the DeltapH across the membrane, particularly at Ca2+ concentrations (approximately 500 microM) found optimal for the antiporter activity. Similarly, H+ release induced by Ca2+ increased with the magnitude of DeltapH. However, above 60% DeltapH (high H(+)-pump activity), the net H+ release from the vesicles decreased as the pump-mediated H+ influx exceeded the Ca(2+)-induced H+ efflux. We also observed that the Ca2+/H+ antiport activity depends, essentially, on the DeltapH component of the electrochemical gradient (approximately 3 nmol Ca2+ taken up/mg protein), although the Deltaphi component may also support some Ca2+ accumulation by the vesicles (approximately 1 nmol/mg protein) in the absence of DeltapH. Both Ca(2+)-induced H+ release and DeltapH-dependent Ca2+ uptake could be driven by an artificially imposed proton motive force. Under normal conditions (H+ pump-induced DeltapH), the electrochemical gradient dependence of Ca2+ uptake by the vesicles was checked by inhibition of the process with specific inhibitors (bafilomycin A(1), ergocryptin, folymicin, DCCD) of the H(+)-pump activity. These results indicate that synaptic vesicles Ca2+/H+ antiport is indirectly linked to ATP hydrolysis and it is essentially dependent on the chemical component (DeltapH) of the electrochemical gradient generated by the H(+)-pump activity.
Collapse
Affiliation(s)
- P P Gonçalves
- Centro de Biologia Celular, Departamento de Biologia, Universidade de Aveiro, 3810, Aveiro, Portugal.
| | | | | | | |
Collapse
|
23
|
Mouro I, Halleck MS, Schlegel RA, Mattei MG, Williamson P, Zachowski A, Devaux P, Cartron JP, Colin Y. Cloning, expression, and chromosomal mapping of a human ATPase II gene, member of the third subfamily of P-type ATPases and orthologous to the presumed bovine and murine aminophospholipid translocase. Biochem Biophys Res Commun 1999; 257:333-9. [PMID: 10198212 DOI: 10.1006/bbrc.1999.0347] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recently, a P-type ATPase was cloned from bovine chromaffin granules (b-ATPase II) and a mouse teratocarcinoma cell line (m-ATPase II) and was shown to be homologous to the Saccharomyces cerevisiae DRS2 gene, the inactivation of which resulted in defective transport of phosphatidylserine. Here, we report the cloning from a human skeletal muscle cDNA library of a human ATPase II (h-ATPase II), orthologous to the presumed bovine and mouse aminophospholipid translocase (95.3 and 95.9% amino acid identity, respectively). Compared with the bovine and mouse counterparts, the cloned h-ATPase II polypeptide exhibits a similar membrane topology, but contains 15 additional amino acids (1163 vs 1148) located in the second intracytoplasmic loop, near the DKTGTLT-phosphorylation site. However, RT-PCR analysis performed with RNA from different human tissues and cell lines revealed that the coding sequence for these 15 residues is sometimes present and sometimes absent, most likely as a result of a tissue-specific alternative splicing event. The h-ATPase II gene, which was mapped to chromosome 4p14-p12, is expressed as a 9.5-kb RNA species in a large variety of tissues, but was not detected in liver, testis, and placenta, nor in the erythroleukemic cell line K562.
Collapse
Affiliation(s)
- I Mouro
- INSERM U76, Institut National de la Transfusion Sanguine, Paris, France.
| | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Parsons SM, Rogers GA, Gracz LM. Photoaffinity labeling of vesicular acetylcholine transporter from electric organ of Torpedo. Methods Enzymol 1998; 296:99-116. [PMID: 9779443 DOI: 10.1016/s0076-6879(98)96009-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Affiliation(s)
- S M Parsons
- Department of Chemistry, University of California, Santa Barbara 93106, USA
| | | | | |
Collapse
|
25
|
Gonçalves PP, Meireles SM, Gravato C, Vale MG. Ca2+-H+ antiport activity in synaptic vesicles isolated from sheep brain cortex. Neurosci Lett 1998; 247:87-90. [PMID: 9655599 DOI: 10.1016/s0304-3940(98)00256-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Synaptic vesicles isolated from sheep brain cortex exhibit an ATP-dependent Ca2+ accumulation that is inhibited by the protonophore uncoupler carbonyl cyanide m-chorophenylhydrazone (CCCP) and completely released by the Ca2+ ionophore ionomycin. This transport activity was sensitive to the V-type ATPase inhibitor, bafilomycin, but not to the P-type ATPase inhibitor, vanadate. We also observed that the proton gradient, established across the synaptic vesicle membranes in the presence of ATP, is partially dissipated by the addition of Ca2+ (100-860 microM) in correlation to an increase of ATP hydrolysis by the H+-pumping ATPase. In contrast, the activity of the H+-ATPase, measured under uncoupling conditions (presence of CCCP), appears to be unaltered by the calcium ion. The Ca2+-induced H+ release visualized by fluorescence quenching of acridine orange correlates well with the Ca2+ uptake determined isotopically. These results indicate that synaptic vesicles accumulate Ca2+, via a low affinity Ca2+-H+ antiport system energized by the protonmotive force originated from the H+-pumping ATPase activity.
Collapse
Affiliation(s)
- P P Gonçalves
- Departamento de Biologia, Universidade de Aveiro, Portugal.
| | | | | | | |
Collapse
|
26
|
Rodríguez de Lores Arnaiz G, Pellegrino de Iraldi A. Mg2+/Ca(2+)-ATPase activity is not enriched in synaptic vesicles isolated from rat cerebral cortex. Neurochem Res 1997; 22:293-6. [PMID: 9051664 DOI: 10.1023/a:1022490822175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Neuronal ATPases comprise a wide variety of enzymes which are not uniformly distributed in different membrane preparations. Since purified vesicle fractions have Mg2+/Ca(2+)-ATPase, the purpose of the present study was to know whether such enzyme activities have a preferential concentration in a synaptic vesicle fraction in order to be used as markers for these organelles. Resorting to a procedure developed in this Institute, we fractionated the rat cerebral cortex by differential centrifugation following osmotic shock of a crude mitochondrial fraction and separated a purified synaptic vesicle fraction over discontinuous sucrose gradients. Mg2+/Ca(2+)-ATPase activities and ultrastructural studies of isolated fractions were carried out. It was observed that similar specific activities for Mg2+/Ca(2+)-ATPases were found in all fractions studied which contain synaptic vesicles and/or membranes. Although the present results confirm the presence of Mg2+ and Ca(2+)-ATPase activities in synaptic vesicles preparations, they do not favor the contention that Mg2+/Ca(2+)-ATPase is a good marker for synaptic vesicles.
Collapse
Affiliation(s)
- G Rodríguez de Lores Arnaiz
- Instituto de Biología Celular y Neurociencias Prof. Eduardo De Roberts Facultad de Medicina, Universidad de Buenos Aires, Argentina
| | | |
Collapse
|
27
|
Fujiia JT, Su FT, Woodbury DJ, Kurpakus M, Hu XJ, Pourcho R. Plasma membrane calcium ATPase in synaptic terminals of chick Edinger-Westphal neurons. Brain Res 1996. [DOI: 10.1016/0006-8993(96)00638-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
28
|
Tang X, Halleck MS, Schlegel RA, Williamson P. A subfamily of P-type ATPases with aminophospholipid transporting activity. Science 1996; 272:1495-7. [PMID: 8633245 DOI: 10.1126/science.272.5267.1495] [Citation(s) in RCA: 352] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The appearance of phosphatidylserine on the surface of animal cells triggers phagocytosis and blood coagulation. Normally, phosphatidylserine is confined to the inner leaflet of the plasma membrane by an aminophospholipid translocase, which has now been cloned and sequenced. The bovine enzyme is a member of a previously unrecognized subfamily of P-type adenosine triphosphatases (ATPases) that may have diverged from the primordial enzyme before the separation of the known families of ion-translocating ATPases. Studies in Saccharomyces cerevisiae suggest that aminophospholipid translocation is a general function of members of this family.
Collapse
Affiliation(s)
- X Tang
- Department of Biology, Amherst College, MA 01002, USA
| | | | | | | |
Collapse
|
29
|
Yakir N, Rahamimoff R. The non-specific ion channel in Torpedo ocellata fused synaptic vesicles. J Physiol 1995; 485 ( Pt 3):683-97. [PMID: 7562610 PMCID: PMC1158037 DOI: 10.1113/jphysiol.1995.sp020762] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1. Synaptic vesicles were isolated and fused into large structures with a diameter of more than 20 microns to characterize their ionic channels. The 'cell'-attached and inside-out configurations of the patch clamp technique were used. 2. Two types of ion channels were most frequently observed: a low conductance chloride channel and a high conductance non-specific channel. 3. The non-specific channel has a main conducting state and a substate. The main conducting state has a slope conductance of 246 +/- 15 pS (+/- S.E.M., n = 15), in the presence of different combinations of KCl and potassium glutamate. 4. From the reversal potentials of the current-voltage (I-V) relation, it was concluded that this channel conducts both Cl- and K+. 5. The non-specific channel is highly voltage dependent: under steady-state voltages it has a high open probability near 0 mV and does not inactivate; when the membrane is hyperpolarized (pipette side more positive), the open probability decreases dramatically. 6. Voltage pulses showed that upon hyperpolarization (from holding potentials between -20 and + 20 mV), the channels deactivated; when the membrane was stepped back to the holding potential, the channels reactivated rapidly. 7. In a number of experiments, when the pipette side was made more negative than the bath, the open probability also decreased. 8. Frequently, a substate with a conductance of about 44 +/- 4% (+/- S.E.M., n = 3) of the main state was detected. 9. We speculate that this non-specific ion channel may have different roles at the various stages of the life cycle of the synaptic vesicle. When the synaptic vesicle is an intracellular structure, it might help its transmitter-concentrating capacity by dissipating the polarization. After fusion with the surface membrane, it might constitute an additional conductance pathway, taking part in frequency modulation of synaptic transmission.
Collapse
Affiliation(s)
- N Yakir
- Department of Physiology, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | | |
Collapse
|
30
|
Williamson P, Schlegel RA. Back and forth: the regulation and function of transbilayer phospholipid movement in eukaryotic cells. Mol Membr Biol 1994; 11:199-216. [PMID: 7711830 DOI: 10.3109/09687689409160430] [Citation(s) in RCA: 164] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
That some membranes restrict certain lipid species to one side of the bilayer and others to the opposite side has been known for two decades. However, how this asymmetric transbilayer distribution is generated and controlled, how many and what type of membranes are so structured, and even the reason for its existence is just now beginning to be understood. It has been a decade since the discovery of an activity which transports in an ATP-dependent manner only the aminophospholipids from the outer to the inner leaflet of the plasma membrane. This aminophospholipid translocase has yet to be isolated, reconstituted, and identified molecularly. Elevating intracellular Ca2+ allows all the major classes of phospholipids to move freely across the bilayer, scrambling lipids and dissipating asymmetry. The nature of this pathway and its mode of activation by Ca2+ remain to be determined. Though loss of transbilayer asymmetry by blood cells clearly produces a procoagulant surface and increases interactions with the reticuloendothelial system, it remains to be elucidated whether maintenance of blood homeostasis is just one expression of a more general raison d'être for lipid asymmetry. It is these persisting uncertainties and gaps in our knowledge which make the field such an interesting and exciting challenge at the present time.
Collapse
Affiliation(s)
- P Williamson
- Department of Biology, Amherst College, MA 01002
| | | |
Collapse
|
31
|
Woodruff RI, Telfer WH. Steady-state gradient in calcium ion activity across the intercellular bridges connecting oocytes and nurse cells in Hyalophora cecropia. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 1994; 25:9-20. [PMID: 8292820 DOI: 10.1002/arch.940250103] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Intracellular activities of K+, H+, Mg2+, Ca2+, and Cl-, measured with ion selective microelectrodes in the oocyte and the nurse cells in ovarian follicles of Hyalophora cecropia, indicated that a Ca2+ current is a key component of the electrical potential that is maintained across the intercellular bridges connecting these two cells. In vitellogenic follicles, Ca2+ activity averaged 650 nM in the oocyte and 190 nM in the nurse cells, whereas activities of the other ions studied differed between these cells by no more than 6%. Incubation in 200 microM ammonium vanadate caused a reversal of electrical potential from 8.3 mV, nurse cell negative, to 3.0 mV, oocyte negative, and at the same time the Ca2+ gradient was reversed: activities rose to an average 3.0 microM in the nurse cells and 1.6 microM in the oocyte, whereas transbridge ratios of the other cations remained at 0-3%. In immature follicles that had not yet initiated their transbridge potentials, Ca2+ activities averaged approximately 2 microM in both oocyte and nurse cells. The results suggest that vitellogenic follicles possess a vanadate-sensitive Ca2+ extrusion mechanism that is more powerful in the nurse cells than in the oocyte.
Collapse
Affiliation(s)
- R I Woodruff
- Department of Biology, West Chester University, PA 19383
| | | |
Collapse
|
32
|
Brochier G, Morel N. The same 15 kDa proteolipid subunit is a constituent of two different proteins in Torpedo, the acetylcholine releasing protein mediatophore and the vacuolar H+ ATPase. Neurochem Int 1993; 23:525-39. [PMID: 8281121 DOI: 10.1016/0197-0186(93)90100-j] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Using the monoclonal antibody 15K1, we have studied, at the cellular and subcellular levels, the distribution of a 15 kDa proteolipid, identified as the subunit of mediatophore, a presynaptic membrane protein able to release acetylcholine when activated by calcium. Aside from the electric lobe, the antigen distribution in the brain of Torpedo paralleled that of the synaptic vesicle antigen SV2 and did not appear to be related to that of acetylcholine and choline acetyltransferase. The 15 kDa proteolipid antigen was therefore present in all nerve endings and not restricted to cholinergic ones. At the ultrastructural level, on cholinergic nerve endings, the antigen was detected associated to synaptic vesicles and, to a lesser extent, to the presynaptic plasma membrane. Indeed, considering the high sequence homology between the mediatophore subunit (Birman et al., 1990) and the proteolipid subunit of the vacuolar type H+ ATPase, a major enzyme constituent of synaptic vesicles, this distribution was not surprising. To determine whether antibody 15K1 recognizes the vacuolar type H+ ATPase, we chose a non neuronal cell type which possesses a high content of this enzyme, the kidney proton secreting epithelial cells. Indeed, antibody 15K1 intensely labelled the apical plasma membrane of mitochondria rich epithelial cells in kidney tubules. A high density of the antigen was also found associated to intracellular membrane structures such as lysosomal multivesicular bodies, both in kidney epithelial cells and in electromotoneurons. The 15 kDa proteolipid antigen was associated with other vacuolar H+ ATPase subunits in kidney membranes which was not the case in presynaptic plasma membranes. This illustrates that the 15 kDa proteolipid antigen is a constituent of two different protein complexes, which exhibit very different functional properties.
Collapse
Affiliation(s)
- G Brochier
- Department Neurochimie, Laboratoire Neurobiologie Cellulaire et Moleculaire C.N.R.S., Gif sur Yvette, France
| | | |
Collapse
|
33
|
Parsons SM, Bahr BA, Rogers GA, Clarkson ED, Noremberg K, Hicks BW. Acetylcholine transporter--vesamicol receptor pharmacology and structure. PROGRESS IN BRAIN RESEARCH 1993; 98:175-81. [PMID: 8248506 DOI: 10.1016/s0079-6123(08)62396-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- S M Parsons
- Department of Chemistry, University of California, Santa Barbara 93106
| | | | | | | | | | | |
Collapse
|
34
|
Parsons SM, Prior C, Marshall IG. Acetylcholine transport, storage, and release. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1993; 35:279-390. [PMID: 8463062 DOI: 10.1016/s0074-7742(08)60572-3] [Citation(s) in RCA: 163] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
ACh is released from cholinergic nerve terminals under both resting and stimulated conditions. Stimulated release is mediated by exocytosis of synaptic vesicle contents. The structure and function of cholinergic vesicles are becoming known. The concentration of ACh in vesicles is about 100-fold greater than the concentration in the cytoplasm. The AChT exhibits the lowest binding specificity among known ACh-binding proteins. It is driven by efflux of protons pumped into the vesicle by the V-type ATPase. A potent pharmacology of the AChT based on the allosteric VR has been developed. It has promise for clinical applications that include in vivo evaluation of the density of cholinergic innervation in organs based on PET and SPECT. The microscopic kinetics model that has been developed and the very low transport specificity of the vesicular AChT-VR suggest that the transporter has a channel-like or multidrug resistance protein-like structure. The AChT-VR has been shown to be tightly associated with proteoglycan, which is an unexpected macromolecular relationship. Vesamicol and its analogs block evoked release of ACh from cholinergic nerve terminals after a lag period that depends on the rate of release. Recycling quanta of ACh that are sensitive to vesamicol have been identified electrophysiologically, and they constitute a functional correlate of the biochemically identified VP2 synaptic vesicles. The concept of transmitter mobilization, including the observation that the most recently synthesized ACh is the first to be released, has been greatly clarified because of the availability of vesamicol. Differences among different cholinergic nerve terminal types in the sensitivity to vesamicol, the relative amounts of readily and less releasable ACh, and other aspects of the intracellular metabolism of ACh probably are more apparent than real. They easily could arise from differences in the relative rates of competing or sequential steps in the complicated intraterminal metabolism of ACh rather than from fundamental differences among the terminals. Nonquantal release of ACh from motor nerve terminals arises at least in part from the movement of cytoplasmic ACh through the AChT located in the cytoplasmic membrane, and it is blocked by vesamicol. Possibly, the proteoglycan component of the AChT-VR produces long-term residence of the macromolecular complex in the cytoplasmic membrane through interaction with the synaptic matrix. The preponderance of evidence suggests that a significant fraction of what previously, heretofore, had been considered to be nonquantal release from the motor neuron actually is quantal release from the neuron at sites not detected electrophysiologically.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
Affiliation(s)
- S M Parsons
- Department of Chemistry, University of California, Santa Barbara 93106
| | | | | |
Collapse
|
35
|
Clarkson ED, Rogers GA, Parsons SM. Binding and active transport of large analogues of acetylcholine by cholinergic synaptic vesicles in vitro. J Neurochem 1992; 59:695-700. [PMID: 1629738 DOI: 10.1111/j.1471-4159.1992.tb09424.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A previous structure-activity investigation of acetylcholine (ACh) revealed a positive correlation between additional hydrophobic bulk and increased potency for inhibition of active transport of [3H]ACh by synaptic vesicles isolated from the electric organ of Torpedo. In the current study, several ACh analogues that are significantly larger than previously studied "false transmitters" were synthesized in the tritiated form by chemical means and tested for active transport. These are analogue 14 [(+/-)-(cis,trans)-1-benzyl-1-methyl-3-acetoxypyrrolidinium iodide], analogue 15 [(+/-)-1,1-dimethyl-3-benzoyloxypyrrolidinium iodide], and analogue 16/17 [(+/-)-(cis,trans)-1-benzyl-1-methyl-3-benzoyloxypyrrolidinium iodide]. These analogues place significant additional hydrophobic bulk on one or the other (analogues 14 and 15) or both (analogue 16/17) of the two pharmacophores of a small, conformationally constrained analogue of ACh. [3H]Analogue 14 and [3H]analogue 15 are actively transported, with Vmax values the same as or less than that of ACh, depending on the vesicle preparation. The observation that Vmax is the same for an analogue and ACh in some vesicle preparations suggests that the rate-limiting step does not involve ACh bound to the transporter. [3H]Analogue 16/17 is actively transported very poorly. Km values for ACh and for transported ACh analogues vary by up to two- to threefold in different vesicle preparations. The ACh transporter is much less selective for transported substrates than anticipated.
Collapse
Affiliation(s)
- E D Clarkson
- Department of Chemistry, University of California, Santa Barbara 93106
| | | | | |
Collapse
|