Cellular & molecular Ca2+ microdomains in olfactory cilia support low signaling amplification of odor transduction
Ezine
- Published: Oct 11, 2010
- Channels: UV/Vis Spectroscopy
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Cellular & molecular Ca2+ microdomains in olfactory cilia support low signaling amplification of odor transduction European Journal of Neuroscience 2010, 32, 932-938 Abstract: Signal transduction depends critically on the spatial localization of protein constituents. A key question in odor transduction is whether chemotransduction proteins organize into discrete molecular complexes throughout olfactory cilia or distribute homogeneously along the ciliary membrane. Our recordings of Ca2+ changes in individual cilia with unprecedented spatial and temporal resolution, by the use of two-photon microscopy, provide solid evidence for Ca2+ microdomains (transducisomes). Dissociated frog olfactory neurons were preloaded with caged-cAMP and fluo-4 acetoxymethyl ester probe Ca2+ indicator. Ca2+ influx through cyclic nucleotide-gated (CNG) channels was evoked by uniformly photoreleasing cAMP, while ciliary Ca2+ was measured. Discrete fluorescence events were clearly resolved. Events were missing in the absence of external Ca2+, consistent with the absence of internal Ca2+ sources. Fluorescence events at individual microdomains resembled single-CNG channel fluctuations in shape, mean duration and kinetics, indicating that transducisomes typically contain one to three CNG channels. Inhibiting the Na+/Ca2+ exchanger or the Ca2+-ATPase prolonged the decay of evoked intraciliary Ca2+ transients, supporting the participation of both transporters in ciliary Ca2+ clearance, and suggesting that both molecules localize close to the CNG channel. Chemosensory transducisomes provide a physical basis for the low amplification and for the linearity of odor responses at low odor concentrations.
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