title: Involvement of vH(+)-ATPase in synaptic vesicle swelling.
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.
authors.affiliation: Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA.
authors.forename: Leah
authors.initials: L
authors.lastname: Shin
authors.forename: Nirukti
authors.initials: N
authors.lastname: Basi
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Jeremic
authors.forename: Jin-Sook
authors.initials: JS
authors.lastname: Lee
authors.forename: Won Jin
authors.initials: WJ
authors.lastname: Cho
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Chen
authors.forename: Rania
authors.initials: R
authors.lastname: Abu-Hamdah
authors.forename: David
authors.initials: D
authors.lastname: Oupicky
authors.forename: Bhanu P
authors.initials: BP
authors.lastname: Jena
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D051403:Aquaporin 6 / Q000378:metabolism; D015153:Blotting, Western; D005089:Exocytosis; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D051381:Rats; D017207:Rats, Sprague-Dawley; D013572:Synaptic Vesicles / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism; D050988:Vesicle-Associated Membrane Protein 2 / Q000378:metabolism
chemical_list: D051403:Aquaporin 6; D050988:Vesicle-Associated Membrane Protein 2; D000251:Adenosine Triphosphatases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go