The G-Proteins Regulating Phosphoinositide Breakdown
The stimulation of phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis is a widespread cellular response to many hormones, growth factors and neurotransmitters (Berridge 1987). It is catalyzed by a phospholipase C (PLC) and yields two signaling molecules: inositol 1,4,5-trisphosphate (IP3) which releases Ca2+ from stores in the endoplasmic reticulum, and 1,2-diacylglycerol (DAG) which activates protein kinase C. The growth factors activate the PLC through the tyrosine kinase activity of their receptors (Kriz et al 1990), whereas the other agonists act through guanine nucleotide-binding regulating proteins (G-proteins). Despite the recognition several years ago that G-proteins were involved in the regulation of PLC, some of these G-proteins have only recently been identified (Taylor et al 1990, Smrcka et al 1991, Blank et al 1991). These G-proteins are insensitive to pertussis toxin, but it is clear that toxin-insensitive G-proteins are also involved in the regulation of PLC in some tissues (Exton 1988).
KeywordsPertussis Toxin Bovine Brain Bovine Liver Liver Plasma Membrane Inositol Trisphosphate
Unable to display preview. Download preview PDF.
- Blank JL, Ross AH, Exton JH (1991) Purification and characterization of two G-proteins which activate the β 1 isozyme of phosphoinositide-specific phospholipase C. Identifiction as members of the Gq class. J Biol Chem In pressGoogle Scholar
- Kriz R, Lin L-L, Sultzman L, Ellis C, Heldin C-H, Pawson T, Knopf J (1990) Phospholipase C isozymes: structural and functional similarities. In: Protooncogenes in cell development. Wiley, Chichester (Ciba Foundation Symposium 150) p 112–127Google Scholar
- Taylor SJ, Chae HZ, Rhee SG, Exton JH (1991) Activation of the β1 isozyme of phospholipase C by purified α subunits of the Gq class of G proteins. Nature In pressGoogle Scholar