Two forms of rat phospholipase C-b3 generated by alternative splicing

Abstract

Phospholipase C-β3 is a crucial signal transduction enzyme that catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate($PIP_2$) to produce two second messenger molecules, inositol 1,4,5-triphosphate($IP_3$) and diacylglycerol(DAG). During we performed cDNA cloning studies of PLC-β3 in rat brain by screening, A full length cDNA clone(4176 base) and a shorter cDNA clone(3955 base), which lacked the region(201 bases) corresponding to PH domain at the N-terminal were isolated. Using RT-PCR, we confirmed that alternatively splicing mRNAs were generated by co- transcription from the same gene in various tissues. Relative amount of these mRNAs was determined by RNase protection assay and the ratio of the major mRNA to the minor mRNA was estimated to be 1:2.5, 1:1, 1:5, 1:4.5, 1:1.7, 1:2.5 in brain, heart, kidney, liver, lung, and testis, respectively. Also, polyclonal antibodies were raised against synthetic peptides including the PH domain portions of PLC-β3. Western blot analysis with these antibodies revealed that 150kD protein was only expressed in tissues. Supposed that two mRNA were translated in tissues, we postulate that the protein which lacks PH domain has another unknown function in the cytosol, because PH domain is essential to the role of PLC-β3.