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 calci um signals and regulating important aspects of cellular physiology and gene expression. To further our understanding of InsP(3)Rs we have characterise d InsP(3)Rs and the InsP(3)R gene, itr-1, from the model organism Caenorhab ditis elegans. cDNAs encoding InsP(3)Rs were cloned enabling us to: (a) ide ntify three putative transcription start sites that result in alternative m RNA 5' ends: (b) detect alternative splicing at three sites and: (c) determ ine 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 conse rved structural features. When the putative InsP(3) binding domain was expr essed 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 mem branes. These antibodies and itr-1::GFP (green fluorescent protein) reporte r constructs were used to determine the expression pattern of itr-1 in C. e legans. Strong expression was observed in the intestine, pharynx, nerve rin g, excretory cell and gonad. These results demonstrate the high degree of s tructural and functional conservation of InsP(3)Rs from nematodes to mammal s and the utility of C. elegans as a system for studies on InsP(3)R mediate d signalling. (C) 1999 Academic Press.