FBS Colloquia No.233Physiological Laboratory

Ion channels and its effector molecules expressed on the cell membrane of fine structure

The function of ion channels which expressed on the cell membrane are investigated from various viewpoints. However, there are limited information about the kinetics of the channel on the cell membrane in flagella and cilia, mostly because of the technical limitations involved in studying such narrow spaces and fine structures. In this colloquium, two researchers will introduce the modulation mechanism of ion channels existing in such special structures, focusing on the olfactory cilia, and flagella of sperm, with the latest data. Olfactory cilia is the place of olfactory transduction, its cylindrical cilia have a diameters of 100–200 nm. Cyclic nucleotide-gated (CNG) and Ca2+-activated Cl (Cl(Ca)) channels open by cytoplasmic cAMP or Ca2+. However, it is little known that these molecular dynamics in the cilia. In this study, we could visualize Ca2+ signals with Fluo-4 and record channel activity, simultaneously, and considered the cytoplasmic Ca dynamics in fine structure olfactory cilia. Flagellum of spermatozoa has been reported to express several types of sperm-specific ion channels (K+ channels and Ca2+ channels). It also expresses an unique membrane protein, voltage-sensing phosphatase (VSP) which shows voltage-dependent phosphatase activity toward phophoinositides. So far, however, the biological significance of VSP has been elusive. Here, we report that VSP regulates sperm-specific ion channels, playing important roles in sperm function.