CLONING AND FUNCTIONAL EXPRESSION OF A CYCLIC-NUCLEOTIDE-GATED CHANNEL FROM MAMMALIAN SPERM

CYCLIC nucleotide-gated (CNG) channels serve as downstream targets of signalling pathways in vertebrate photoreceptor cells and olfactory se nsory neurons (see ref. 1 for review). Ca2+ ions that enter through CN G channels(2-5) intimately control these signalling pathways by regula ting synthesis(6) or hydrolysis(7) of cyclic nucleotides, and by decre asing ligand sensitivity of CNG channels(8). Several lines of evidence suggest that cyclic nucleotides and Ca2+ play important roles in chemo taxis of invertebrate sperm and fertilization (see ref. 9 for review), whereas their mechanisms of action in vertebrate sperm are largely un known. Here we report the cloning and functional expression of a novel CNG channel from bovine testis. The channel polypeptide was functiona lly localized in sperm, but is also specifically expressed in cone pho toreceptor cells. These channels might be involved in chemotaxis of sp erm by controlling Ca2+ entry through a cyclic-nucleotide signalling p athway.