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.
