Artificially imposed electrical potentials drive L-glutamate uptake into synaptic vesicles of bovine cerebral cortex.
L-Glutamate is a major excitatory neurotransmitter in the central nervous system. MgATP-dependent glutamate uptake and H(+)-pumping ATPase activity were reported in highly purified synaptic vesicles [Naito & Ueda (1983) J. Biol. Chem. 258, 696-699; Shioi, Naito & Ueda (1989) Biochem. J. 258, 499-504], and it is hypothesized that an electrochemical H+ gradient across the vesicle membrane, the so-called protonmotive force, elicits the neurotransmitter uptake. An inside-positive diffusion potential across the vesicle membrane was established with valinomycin plus Rb+. This artificial electrical potential promoted the uptake of glutamate, but not aspartate, in the synaptic vesicles prepared from bovine cerebral cortex. The uptake was inhibited by the protonmotive-force dissipators carbonyl cyanide p-trifluoro-methoxyphenylhydrazone or nigericin, and was enhanced by concomitant imposition of a pH jump (alkalinization) in the external medium. Subcellular and subvesicular distributions showed the uptake system to be predominantly associated with small synaptic vesicles. The results support the hypothesis that glutamate uptake into synaptic vesicles is coupled with a H+ efflux down the electrochemical potential gradient, which is generated by H(+)-pumping ATPase.
Shioi
J
J
Mental Health Research Institute, University of Michigan, Ann Arbor 48109.
Ueda
T
T
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002414:Cations, Monovalent; D002417:Cattle; D002540:Cerebral Cortex / Q000378:metabolism* / Q000648:ultrastructure; D004563:Electrochemistry; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials; D009550:Nigericin / Q000494:pharmacology; D011522:Protons; D012413:Rubidium / Q000494:pharmacology; D013572:Synaptic Vesicles / Q000378:metabolism*; D014634:Valinomycin / Q000494:pharmacology
D002352:Carrier Proteins; D002414:Cations, Monovalent; D005971:Glutamates; D011522:Protons; D014634:Valinomycin; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D018698:Glutamic Acid; D000255:Adenosine Triphosphate; D012413:Rubidium; D009550:Nigericin