APPEARANCE OF A NOVEL CA2-LIKE (TRPL) PROTEIN OF DROSOPHILA( INFLUX PATHWAY IN SF9 INSECT CELLS FOLLOWING EXPRESSION OF THE TRANSIENT RECEPTOR POTENTIAL)

Activation of phospholipase C, elevation of free cytosolic Ca2+ concen tration ([Ca2+](i)) and stimulation of Ca2+ influx have been implicate d in Drosophila phototransduction. Electrophysiological studies sugges t that trp and trpl proteins may be important for the light-activated Ca2+ current found in Drosophila photoreceptor cells. Although these p roteins exhibit homologies to voltage-gated Ca2+ and Na+ channels, the ir actual function in insect cells and their relation to proteins invo lved in mammalian cell Ca2+ signaling remains unknown. In the present study, [Ca2+](i) was examined in fura-2-loaded Sf9 insect cells infect ed with recombinant baculovirus containing cDNA for the trpl protein. Ca2+ influx was examined by use of Ba2+, a Ca2+ surrogate that is not a substrate for Ca2+-pumps or carriers and by measurement of whole-cel l membrane currents. The results suggest that expression of trpl is as sociated with appearance of a Ca2+ permeable, non-selective cation cha nnel formed by the trpl protein. (C) 1994 Academic Inc.