Inositol 1,4,5-trisphosphate receptors are strongly expressed in the nervous system, pharynx, intestine, gonad and excretory cell of Caenorhabditis elegans and are encoded by a single gene (itr-1)

Inositol 1,4,5-trisphosphate (InsP(3)) activates receptors (InsP(3)Rs) that mediate intracellular Ca2+ release, thereby modulating intracellular calcium signals and regulating important aspects of cellular physiology and gene expression. To further our understanding of InsP(3)Rs we have characterised InsP(3)Rs and the InsP(3)R gene, itr-1, from the model organism Caenorhabditis elegans. cDNAs encoding InsP(3)Rs were cloned enabling us to: (a) identify three putative transcription start sites that result in alternative mRNA 5' ends: (b) detect alternative splicing at three sites and: (c) determine the full genomic organisation of the itr-1 gene. The InsP(3)R protein (ITR-1) is similar to 42% identical with known InsP(3)Rs and possesses conserved structural features. When the putative InsP(3) binding domain was expressed in Escherichia coli, specific binding of InsP(3) was detected. Using antibodies against ITR-1 we detected a protein of 220 kDa in C. elegans membranes. These antibodies and itr-1::GFP (green fluorescent protein) reporter constructs were used to determine the expression pattern of itr-1 in C. elegans. Strong expression was observed in the intestine, pharynx, nerve ring, excretory cell and gonad. These results demonstrate the high degree of structural and functional conservation of InsP(3)Rs from nematodes to mammals and the utility of C. elegans as a system for studies on InsP(3)R mediated signalling. (C) 1999 Academic Press.