The inositol 1,4,5-triphosphate receptor expression in Drosophila suggests a role for IP₃ signalling in muscle development and adult chemosensory functions

Abstract

Inositol 1,4,5-triphosphate (IP₃) is generated as a second messenger in many diverse cellular signalling pathways. In general these signalling pathways activate a membrane-bound phospholipase C, which cleaves the phospholipid phosphatidylinositol bisphosphate to generate IP₃ and diacylglycerol. IP₃ binds to a specific intracellular receptor, which is a membrane protein and a ligand-gated Ca²⁺ channel, that causes Ca²⁺ release from intracellular stores. The inositol 1,4,5-triphosphate receptor (IP₃R) is thus an integral part of the IP₃ signalling pathway and can be used as a marker to identify biological processes that use IP₃ as a second messenger. We have used an affinity-purified antibody, directed against a bacterial fusion protein and containing 339 amino acids of the Drosophila IP₃R, to detect this protein in adult heads and during embryonic and pupal development. Our results suggest that in Drosophila the IP₃ signalling pathway is used during muscle development; primarily when myoblasts undergo rapid multiplication, in both embryos and pupae. In adults, IP₃ is probably a second messenger in more than one sensory transduction pathway, as well as in other as yet undefined brain and muscle functions.