[Second messengers and protein phosphorylation in cellular signal transduction].
Protein phosphorylation has been recognized as a major mechanism by which cellular functions are controlled by neurotransmitters and hormones. In this review, applications of molecular biological techniques to the analyses of regulatory mechanisms of protein phosphorylation by four major second messengers, cAMP, cGMP, diacylglycerol, and Ca2+, are described. 1) Complementary DNA of the regulatory subunit of the cAMP-dependent protein kinase was cloned and expressed in E. coli. Point mutations were introduced in order to analyze functional domains of the subunit. 2) The soluble isoform of guanylate cyclase was purified, and a cDNA of its 70-KD subunit was cloned. Cyclic GMP binding to purified cGMP-dependent protein kinase was characterized using a rapid filtration assay. 3) Primary structure of the catalytic subunit of calmodulin-dependent protein phosphatase (calcineurin A) was determined and the presence of the second isoform of the enzyme was shown by the cDNA cloning technique. 4) The regulatory domain of the protein kinase C was expressed in E. coli. Analysis using site-directed mutagenesis revealed that a "zinc finger"-like structure is responsible for the binding of phorbol esters. In these studies, the molecular biological approach has proven to be useful for clarifying the molecular mechanisms of cellular signal transduction related to second messengers and protein phosphorylation.
Kuno
T
T
Department of Pharmacology, Kobe University School of Medicine, Japan.
D000818:Animals; D002118:Calcium / Q000502:physiology; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D015290:Second Messenger Systems / Q000502:physiology*; D015398:Signal Transduction
D011506:Proteins; D011494:Protein Kinases; D002118:Calcium