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

• DOI: 10.1016/j.neuron.2010.11.035
• Publication Date: 2010-12-23T09:19:43Z
• Authors: Zhongsheng Zhang; Khanh T. Nguyen; Ellen F. Barrett; Gavriel David
• Keywords: Mice; Proton-Translocating ATPases; Cytosol; Neuroscience(all); Cell Membrane; Presynaptic Terminals; Action Potentials; Animals; Mice, Transgenic; Synaptic Vesicles; Hydrogen-Ion Concentration; Endocytosis; Exocytosis

Key components of vesicular neurotransmitter release, such as Ca(2+) 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 Ca(2+) 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(+)]) that 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 prefused vesicles, continues to extrude cytosolic H(+) after being exocytotically incorporated into the plasma membrane. The resulting cytosolic alkalinization may facilitate vesicular endocytosis.