Exocytosed protons feedback to suppress the Ca2+ current in mammalian cone photoreceptors.
A proton pump acidifies synaptic vesicles and provides the electrochemical gradient for transmitter uptake. Although external protons can modulate membrane voltage- and ligand-gated conductances, the fate of the protons released when vesicles fuse with the plasma membrane is unclear. In the dark, the glutamate-laden vesicles of cone photoreceptors fuse continuously with the plasma membrane. I now show that vesicular protons feed back to block the nearby calcium channels that mediate release. This local proton-mediated feedback is a novel mechanism through which neurons may regulate the release of transmitter.
DeVries
S H
SH
Department of Ophthalmology and Visual Science, Houston Health Science Center, University of Texas, Houston, TX 77030, USA. s-devries@northwestern.edu
D000143:Acids / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004594:Electrophysiology; D005089:Exocytosis / Q000502:physiology*; D025461:Feedback, Physiological / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008322:Mammals; D017494:Proton Pumps / Q000378:metabolism*; D011522:Protons; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012589:Sciuridae; D013572:Synaptic Vesicles / Q000502:physiology
D000143:Acids; D017494:Proton Pumps; D011522:Protons; D018698:Glutamic Acid; D002118:Calcium