Cloning and characterization of the human phosphoinositide-specific phospholipase C-beta 1 (PLCβ1)

Phospholipase C-beta (PLCβ) catalyses the generation of inositol 1,4,5-trisphosphate (IP ₃) and diacylglycerol (DAG) from phosphatidylinositol 4,5-bisphosphate (IP ₂), a key step in the intracellular transduction of a large number of extracellular signals, including neurotransmitters and hormones modulating diverse developmental and functional aspects of the mammalian central nervous system. Four mammalian isozymes are known (PLCβ1-4), which differ in their function and expression patterns in vivo. We have characterized the human PLCβ1 genomic locus (PLCβ1), cloned two distinct PLCβ1 cDNAs (PLCβ1a and b) and analysed their respective expression patterns in a comprehensive panel of human tissues using quantitative TaqMan technology. The two cDNAs derive from transcripts generated through alternative splicing at their 3' end, and are predicted to encode for PLCβ1 isoforms differing at their carboxy-terminus. The human PLCβ1 isoforms are co-expressed in the same tissues with a distinctly CNS-specific profile of expression. Quantitative differences in PLCβ1 isoform expression levels are observed in some tissues. Transient expression of epitope-tagged versions of the two isoforms followed by immunofluorescence revealed localization of the proteins to the cytoplasm and the inner side of the cell membrane. Finally, we characterized the structure of the PLCβ1 locus and confirmed its mapping to human chromosome 20. (C) 2000 Elsevier Science B.V.