Vesicular ATPase Inserted into the Plasma Membrane of Motor Terminals by Exocytosis Alkalinizes Cytosolic pH and Facilitates Endocytosis

Abstract

SUMMARY Key components of vesicular neurotransmitter release, such as Ca2+ influx and membrane recycling, are affected by cytosolic pH. We measured the pH-sensitive fluorescence of Yellow Fluorescent Protein transgenically expressed in mouse motor nerve terminals, and report that Ca2+ influx elicited by action potential trains (12.5-100 Hz) evokes a biphasic pH change: a brief acidification (~13 nM average peak increase in [H+]), followed by a prolonged alkalinization (~30 nM peak decrease in [H+]) which outlasts the stimulation train. The alkalinization is selectively eliminated by blocking vesicular exocytosis with botulinum neurotoxins, and is prolonged by the endocytosis-inhibitor dynasore. Blocking H+ pumping by vesicular H+-ATPase (with folimycin or bafilomycin) suppresses stimulation-induced alkalinization and reduces endocytotic uptake of FM1-43. These results suggest that H+-ATPase, known to transfer cytosolic H+ into pre-fused vesicles, continues to extrude cytosolic H+ after being exocytotically incorporated into the plasma membrane. The resulting cytosolic alkalinization may facilitate vesicular endocytosis.

Neuronal hyperactivity causes Na+/H+ exchanger-induced extracellular acidification at active synapses

“…Several studies have addressed the question of how neuronal activity elicits changes in intracellular and extracellular H + concentration, sometimes yielding contrasting results (Caldwell et al, 2013;Chen and Chesler, 2015;Cichy et al, 2015;de Curtis et al, 1998;DeVries, 2001;Lu et al, 2012;Palmer et al, 2003;Zhang et al, 2010;Zhao et al, 2011). We studied the effects of sustained heightened neural activity on the extracellular H + concentration by using in vitro models of epileptic-like network states characterized by synchronized neuronal discharges.…”

ATP Binding to Synaspsin IIa Regulates Usage and Clustering of Vesicles in Terminals of Hippocampal Neurons

“…Activity-dependent alterations in the cellular environment, for example, pH changes (Zhang et al, 2010;Svichar et al, 2011;Rangaraju et al, 2014), have the potential to alter the properties of fluorescent proteins. Therefore, the changes in FR that we observed could conceivably reflect environmental effects rather than changes in [ATP] syn (Rangaraju et al, 2014).…”

Synaptic Glutamate Release Is Modulated by the Na+-Driven Cl−/HCO3−Exchanger Slc4a8

“…B, Latency of ictal activity upon pilocarpine injection ( p ϭ 0.01; n ϭ 13/13) was prolonged, as was seizure onset in a mouse pup model of hyperthermia-related epileptic activity (n ϭ 11/10). *p Ͻ 0.05. ties of YFP were successfully used to analyze the presynaptic pH in large motor endplates (Zhang et al, 2010).…”