INTRACELLULAR CA2-OPERATED INFLUX OF CA2+ THROUGH TRP-R, A RAT HOMOLOG OF TRP, EXPRESSED IN XENOPUS OOCYTES( STORE)

To elucidate whether rat transient receptor potential (TRP-R), a rat T RP4 homolog, functions as a store-operated Ca2+ channel (SOC), we have measured the Ca2+ entry after thapsigargin treatment in Xenopus oocyt es injected with mRNA for TRP-R. While non-injected oocytes elicited a n SOC response, significantly larger responses were observed in the oo cytes expressing TRP-R. The oocyte-native SOC response was inhibited b y injection of antisense oligodeoxyribonucleotide for mammalian TRP1. When Ca2+ concentration-SOC response curve was examined, the EC50 valu e was much smaller in oocytes expressing TRP-R than that of non-inject ed oocytes. These results suggest that TRP-R functions as SOC having h igher sensitivity to external Ca2+ than amphibian TRP1 channel. (C) 19 98 Published by Elsevier Science Ireland Ltd. All rights reserved.