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The Journal of Neuroscience, May 4, 2005, 25(18):4672-4680; doi:10.1523/JNEUROSCI.0549-05.2005
Previous Article
Cellular/Molecular
G o2 Regulates Vesicular Glutamate Transporter Activity by Changing Its Chloride Dependence
Sandra Winter,1 *
Irene Brunk,1 *
Diego J. Walther,2
Markus Höltje,1
Meisheng Jiang,3
Jens-Uwe Peter,2
Shigeo Takamori,4
Reinhard Jahn,4
Lutz Birnbaumer,3 and
Gudrun Ahnert-Hilger1
1AG Funktionelle Zellbiologie, Centrum für Anatomie, Charité Universitätsmedizin Berlin, D-10115 Berlin, Germany, 2Max-Planck-Institut für Molekulare Genetik, D-14195 Berlin, Germany, 3National Institute of Environmental Health Sciences, Triangle Park, North Carolina 27709, and 4Max-Planck-Institut für Biophysikalische Chemie, D-37707 Göttingen, Germany
Classical neurotransmitters, including monoamines, acetylcholine, glutamate, GABA, and glycine, are loaded into synaptic vesicles by means of specific transporters. Vesicular monoamine transporters are under negative regulation by subunits of trimeric G-proteins, including G o2 and G q. Furthermore, glutamate uptake, mediated by vesicular glutamate transporters (VGLUTs), is decreased by the nonhydrolysable GTP-analog guanylylimidodiphosphate. Using mutant mice lacking various G subunits, including G o1, G o2, G q, and G 11, and a G o2-specific monoclonal antibody, we now show that VGLUTs are exclusively regulated by G o2. G-protein activation does not affect the electrochemical proton gradient serving as driving force for neurotransmitter uptake; rather, G o2 exerts its action by specifically affecting the chloride dependence of VGLUTs. All VGLUTs show maximal activity at 5 mM chloride. Activated G o2 shifts this maximum to lower chloride concentrations. In contrast, glutamate uptake by vesicles isolated from G o2-/- mice have completely lost chloride activation. Thus, G o2 acts on a putative regulatory chloride binding domain that appears to modulate transport activity of vesicular glutamate transporters.
Key words: G o2; VGLUT; regulation; vesicular transmitter transporter; presynaptic; plasticity; chloride dependence
Received July 20, 2004;
revised March 21, 2005;
accepted March 29, 2005.
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