Expression and Function of Protein Kinases During Mammalian Gametogenesis

Abstract

Publisher Summary This chapter reviews critical stages of mammalian germ cell differentiation during which protein kinases (and their corresponding phosphatases) may be functioning. The chapter emphasizes on those kinases involved with regulating the eukaryotic cell cycle with the bias that gametogenesis represents a specialized and highly regulated series of cell cycle events. The chapter reviews the main classes of protein kinases that are the tyrosine kinases and the serine/threonine kinases. It emphasizes the results from the mouse system and includes results from other organisms, especially in particular stages of gametogenesis in which the mammalian system is poorly understood. It has been established that growth factors and their respective receptor tyrosine kinases function in the mitogenic pathway. Receptor tyrosine kinases consist of three distinct domains: (1) the extracellular ligand binding domain, (2) a transmembrane region, and (3) the intracellular cytoplasmic tyrosine kinase catalytic domain. In the cytoplasmic domain, serine/threonine and tyrosine residues serve as phosphorylation sites that regulate the activity of the receptor tyrosine kinase. Many non-receptor tyrosine kinases have been identified as products of retrovirally encoded oncogenes. Non-receptor tyrosine kinases are divided into two groups: (1) transmembrane and (2) cytosolic families. Cytoplasmic serine/threonine protein kinases catalyze the transfer of phosphate groups to serine and threonine residues of target proteins.