Regulation of Phospholipase C-β₃ Signaling by PDZ domain containing proteins

다국어 초록 (Multilingual Abstract)

Phospholipase C-β isozymes(PLC-β) that mediate G protein-coupled receptor signaling pathway are activated by various extra-cellular signals such as neurotransmitters, hormones, etc. Four isotypes of PLC-β in mammals are differently expressed in various tissues and cell lines. According to some reports, they are selectively activated by the specific ligands. The activation of PLC-β may be determined by distinct factors contributing to specificity in each PLC-β mediated signal transduction. We have identified that carboxyl terminal sequences of PLC-β isozymes harbor putative PDZ-binding motif consisting of different amino acid residues. Many PDZ domain-containing proteins are known to localize at highly specialized sub-membranous regions and to participate in cellular junction formation, receptor or channel clustering and intracellular signaling events. These PDZ-binding motifs of PLC-βs may give the specificity in the signaling pathway by interacting with various PDZ domain-containing proteins. We tried to identify the proteins interacting with C-terminus of PLC-β by using yeast two hybrid system. As a result, Na/H exchanger regulating factor2(NHERF2) from liver cDNA library and Cortactin binding protein I(CortBP1) from brain cDNA library were identified as proteins interacting with PLC-β3. These two molecules interact with PDZ-binding motif of PLC-β3 through their PDZ domain. The Thr and Leu residues in PDZ-binding motif of PLC-β3 are essential to interact with PDZ domain, likely as PDZ domain-mediated interacting mode previously reported. PLC-β3 interacts specifically with NHERF2 or CortBP1, but the other PLC-β isozymes not. When expressed in heterogeneous cells, PLC-β3 and CortBP1 were co-localized in specific subcellular region. In HeLa cells expressing the muscarinic acetylcholine receptor, over-expression of NHERF2 enhanced PLC activity by carbachol stimulation. These studies suggest that NHERF2 and CortBP1 may be the molecular keys to determine the specificity in PLC-β3-mediated signaling pahways, expressing in the different tissues.