Type III cyclic nucleotide phosphodiesterases and insulin action

Publisher Summary This chapter discusses the type III cyclic nucleotide phosphodiesterases and insulin action. The cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) are important intracellular second messengers that mediate the cellular responses to various extracellular stimuli or signals, including light and a number of hormones, peptides, neurotransmitters, autocoids, therapeutic agents, etc. The chapter discusses several cyclic nucleotide phosphodiesterases (PDE) gene families. The chapter describes the common structural pattern of PDE isoenzymes through diagram. Purification and characterization of type III cGI PDEs and molecular cloning of the two type III cGI PDE subfamilies are also discussed in the chapter. Type III cGI PDE activation has a major significance in the insulin action. Insulin is a physiologically important inhibitor of lipolysis and glycogenolysis. Although the precise mechanisms of these actions of insulin are not completely known, insulin inhibition of hormonesensitive lipase/lipolysis in adipose tissue and phosphorylase/glycogenolysis in liver are related at least in part to insulin-induced decrease in both hormone-stimulated accumulations of cAMP and hormone-activated cAMP-dependent protein kinases. The chapter concludes with a discussion on kinase cascades in the regulation of cell metabolism and proliferation by insulin.