Get access

Cellular & molecular Ca2+ microdomains in olfactory cilia support low signaling amplification of odor transduction

Authors

  • Karen Castillo,

    1. Department of Biology, Faculty of Sciences, University of Chile, Santiago, Las Palmeras 3525, Ñuñoa, Santiago 7800024, Chile
    2. Millennium Institute for Cell Dynamics and Biotechnology, University of Chile, Santiago, Chile
    Search for more papers by this author
  • Diego Restrepo,

    1. Department of Cell and Developmental Biology and Neuroscience Program, University of Colorado Denver, CO, USA
    Search for more papers by this author
  • Juan Bacigalupo

    1. Department of Biology, Faculty of Sciences, University of Chile, Santiago, Las Palmeras 3525, Ñuñoa, Santiago 7800024, Chile
    2. Millennium Institute for Cell Dynamics and Biotechnology, University of Chile, Santiago, Chile
    Search for more papers by this author

Juan Bacigalupo, 1Department of Biology, as above.
E-mail: bacigalu@uchile.cl

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.

Ancillary