MOLECULAR DIVERSITY OF CA2-ALPHA-1 SUBUNITS FROM THE MARINE RAY DISCOPYGE-OMMATA( CHANNEL)

In many neurons, transmitter release from presynaptic terminals is tri ggered by Ca2+ entry via dihydropyridine-insensitive Ca2+ channels. We have looked for cDNAs for such channels in the nervous system of the marine ray Discopyge ommata. One cDNA (doe-2) is similar to dihydropyr idine-sensitive L-type channels, and two cDNAs (doe-1 and doe-4) are m ore similar to the subfamily of dihydropyridine-insensitive non-L-type channels. doe-4, which encodes a protein of 2326 aa, most closely res embles a previously cloned N-type channel. doe-1, which encodes a prot ein of 2223 aa, is a member of a separate branch of the non-L-type cha nnels. Northern blot analysis reveals that doe-1 is abundant in the fo rebrain. doe-4 is more plentiful in the electric lobe and, therefore, may control neurotransmitter release in motor nerve terminals. These r esults show that the familial pattern of Ca2+-channel genes has been p reserved from a stage in evolution before the divergence of higher and lower vertebrates >400 million years ago. The cloning of these channe ls may be a useful starting point for elucidating the role of the Ca2 channels in excitation-secretion coupling in nerve terminals.