Cholesterol depletion from the plasma membrane impairs proton and glutamate storage in synaptic vesicles of nerve terminals.

We report that cholesterol depletion with methyl-beta-cyclodextrin (MbetaCD) acutely applied to rat brain synaptosomes is accompanied by an immediate increase in transporter-mediated glutamate release and decrease in exocytotic release. To clarify the possible mechanisms underlying these phenomena, we investigated the influence of MbetaCD on synaptic vesicle acidification and exo/endocytotic process in nerve terminals. As shown by acridine orange fluorescence measurements, the application of MbetaCD to synaptosomes, as well as to isolated synaptic vesicles, led to the gradual leakage of the protons from the vesicles, whereas the application of MbetaCD complexed with cholesterol stimulated additional vesicle acidification and an increase in Ca2+-dependent exocytotic response.