WIDESPREAD EXPRESSION OF INOSITOL 1,4,5-TRISPHOSPHATE RECEPTOR TYPE-1GENE (INSP3R1) IN THE MOUSE CENTRAL-NERVOUS-SYSTEM

The expression of inositol 1,4,5-trisphosphate receptor type 1 (InsP3R 1) in the mouse central nervous system (CNS) was studied by in situ hy bridization. The receptor mRNAs were widely localized throughout the C NS, predominantly in the olfactory tubercle, cerebral cortex, CA1 pyra midal cell layer of the hippocampus, caudate putamen, and cerebellar P urkinje cells, where phosphoinositide turnover is known to be stimulat ed by various neurotransmitter receptors. In the most abundantly expre ssing Purkinje cells, InsP3R1 mRNA appeared to be translocated to the distal dendrites, since a strong hybridization density was observed in the molecular layer of the cerebellum. InsP3R protein is known to for m tetrameric receptor-channel complex. Our preliminary hybridization d ata using probes for three distinct InsP3R subtypes showed preferentia l expression of InsP3R1 in many parts of the CNS. The expression of ot her receptor subtypes (InsP3R2 and InsP3R3) is less efficient, suggest ing that a homotetramer formed of InsP3R1 subtype may play a central p art in InsP3/Ca2+ signalling in the neuronal function, whereas a homot etramer of other subtypes and a possible heterotetramer among subtypes may be involved in differential InsP3/Ca2+ signalling. The chromosoma l localization of the gene coding for InsP3R1 was confirmed on chromos ome 6 but was found to be genetically independent of the Lurcher (Lc) mutation.