Inhibition of Glutamate Uptake and Proton Pumping in Synaptic Vesicles by S‐Nitrosylation

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Abstract
Nitric oxide (NO; including NO-., NO+, and NO-) was found to inhibit glutamate uptake by isolated synaptic vesicles of rat brain. This was observed when two unrelated NO donors, S-nitrosogluthathione and S-nitroso-N-acetylpenicillamine, were used. The primary target of NO is the H(+)-ATPase found in the synaptic vesicles, which leads to dissipation of the electrochemical proton gradient and inhibition of glutamate uptake. Oxyhemoglobin (12 microM) and, to a much lesser extent, methemoglobin protected the vacuolar H(+)-ATPase from inhibition. Inhibition of H+ pumping by NO was reversed by addition of 0.5 mM dithiothreitol. The results indicate that the vacuolar H(+)-ATPase from synaptic vesicles is inhibited by NO by a mechanism that involves S-nitrosylation of critical sulfhydryl groups in the enzyme. The interaction of NO with synaptic vesicles might be of importance for the understanding of the multiple effects of NO in neuro-transmission.

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