Plasma membrane Ca2+-ATPase extrudes Ca2+ from hair cell stereocilia

摘要: Mechanically sensitive hair cells of the auditory and vestibular systems use Ca2+ to control adaptation mechanical transduction, effect frequency tuning, trigger neurotransmitter release, mediate efferent synaptic signaling. To determine role that pumps play in regulation bundle, organelle responsible for mechanoelectrical we localized quantified plasma membrane Ca2+-ATPase (PMCA) bundle. We found each bundle contains approximately 10(6) PMCA molecules or 2000 per square micrometer is principal calmodulin binding protein Consistent with biochemical estimates density, measured extracellular Ca2+-selective electrodes a substantial efflux from bundles. The number magnitude resting suggested should generate current as bundles expel Ca2+. Measurement whole-cell currents revealed transduction-dependent outward was consistent activity PMCA. Finally, dialysis inhibitors led large increase concentration bundles, which suggests plays major regulating concentration. Our data further indicate could elevate close above low level bulk endolymph.