Plasma membrane Ca2 -ATPase in the cilia of olfactory receptor neurons: Possible role in Ca2 clearanceReportar como inadecuado




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Resumen

Olfactory sensory neurons respond to odorants increasing Ca2+ concentrations in their chemosensory cilia. Calcium enters the ciliathrough cAMP-gated channels, activating Ca2+-dependent chloride or potassium channels. Calcium also has a fundamental role inodour adaptation, regulating cAMP turnover rate and the affinity of the cyclic nucleotide-gated channels for cAMP. It has been shownthat a Na+ ⁄ Ca2+ exchanger NCX extrudes Ca2+ from the cilia. Here we confirm previous evidence that olfactory cilia also expressplasma membrane Ca2+-ATPase PMCA, and show the first evidence supporting a role in Ca2+ removal. Both transporters weredetected by immunoblot of purified olfactory cilia membranes. The pump was also revealed by immunocytochemistry andimmunohistochemistry. Inside-out cilia membrane vesicles transported Ca2+ in an ATP-dependent fashion. PMCA activity waspotentiated by luminal Ca2+ K0.5 ¼ 670 nm and enhanced by calmodulin CaM; K0.5 ¼ 31 nm. Both carboxyeosin CE andcalmidazolium reduced Ca2+ transport, as expected for a CaM-modulated PMCA. The relaxation time constant s of the Ca2+-dependent Cl– current 272 ± 78 ms, indicative of luminal Ca2+ decline, was increased by CE 2181 ± 437 ms, by omitting ATP666 ± 49 ms and by raising pH 725 ± 65 ms, suggesting a role of the pump on Ca2+ clearance. Replacement of external Na+ byLi+ had a similar effect s ¼ 442 ± 8 ms, confirming the NCX involvement in Ca2+ extrusion. The evidence suggests that both Ca2+transporters contribute to re-establish resting Ca2+ levels in the cilia following olfactory responses.



Autor: Castillo, Karen; - Delgado Arriagada, Ricardo; - Bacigalupo Vicuña, Juan; -

Fuente: http://repositorio.uchile.cl/



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