PUTATIVE CAPACITATIVE CALCIUM-ENTRY CHANNELS - EXPRESSION OF DROSOPHILA TRP AND EVIDENCE FOR THE EXISTENCE OF VERTEBRATE HOMOLOGS

Capacitative calcium entry is a major pathway through which intracellu lar calcium stores are refilled after stimulation. It has been suggest ed that the protein encoded by the transient receptor potential (trp) gene expressed in Drosophila photoreceptors may be homologous with cap acitative calcium entry channels. Expression of the trp gene product i n Xenopus oocytes led to significant increases in calcium entry only w hen the intracellular calcium stores were depleted. Previous investiga tions have found trp to be uniquely expressed in Drosaphila photorecep tors, but PCR cloning shows that homologous proteins exist in Callipho ra, mouse brain and Xenopus oocytes. It is thus possible that capacita tive calcium entry in Xenopus oocytes is mediated by a homologue of tr p.