Functional analysis of neuronal Ca^<2+> channel domains as targets of therapeutics

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What we found were (1) The interaction of N terminal region of Ga_O and C-terminal domain of α_<1A> subunit causes the voltage-resistant inhibition of P/Q-type channel current. (2) Cytosolic Ca^<2+> is required for the opening of store-operated TRP4 channels, whereas the activation of inositol-1,4,5-trisphosphate receptor (IP_3-R) is required and sufficient for the opening of receptor-activated TRP5 channels. (3) Two cDNAs encoding RNA splicing variants of human Ca^<2+> channel α1B subunit were isolated from human brain cDNA libralies. These variants were RNA splicing variants by genomic analysis. One of the variants lacking the II III linker region formed Ca^<2+>-permeable channel having lowωconotoxin sensitivity, as revealed by exogenous expression in human embryonic kidney (HER) cells. (4) An insect peptide PMP-D2 selectively inhibited R-type Cav2.3 channels. (5) A novel antiamneasic drug, FK960, selectively potentiated N-type Cav2.2 channel current in a protein kinase C-dependent manner. (6) A novel analgesic, ONO-2921, selectively inhibited N- and R- type channel currents due to its specific action on inactivated channels. (7) The store-operated and receptoractivated Ca^<2+> entry in rat cerebral cortical neurons in culture by Fura-2 fluorometry. By RT-PCR analysis, we found the presence of rat TRP1, 3, 5 and 6 mRNAs in neurons. Immunostaninig results also suggest that TRP1 and 5 proteins are expressed in the cultured neurons.