%0 Journal Article
%T Protein-Tyrosine Kinase Signaling in the Biological Functions Associated with Sperm
%A Takashi W. Ijiri
%A A. K. M. Mahbub Hasan
%A Ken-ichi Sato
%J Journal of Signal Transduction
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/181560
%X In sexual reproduction, two gamete cells (i.e., egg and sperm) fuse (fertilization) to create a newborn with a genetic identity distinct from those of the parents. In the course of these developmental processes, a variety of signal transduction events occur simultaneously in each of the two gametes, as well as in the fertilized egg/zygote/early embryo. In particular, a growing body of knowledge suggests that the tyrosine kinase Src and/or other protein-tyrosine kinases are important elements that facilitate successful implementation of the aforementioned processes in many animal species. In this paper, we summarize recent findings on the roles of protein-tyrosine phosphorylation in many sperm-related processes (from spermatogenesis to epididymal maturation, capacitation, acrosomal exocytosis, and fertilization). 1. Introduction Protein-tyrosine kinase (PTK) activity and tyrosine phosphorylation of cellular protein were initially discovered by Hunter and colleagues [1¨C3]; they analyzed the protein kinase activity associated with the protein complex of polyoma virus middle T antigen and viral Src gene product, a cellular counterpart of which is the cellular Src protein. At that time, phosphorylation events on amino acids other than tyrosine (i.e., serine and threonine residues) were already known as posttranslational modifications of physiological importance. However, the discovery of tyrosine phosphorylation for the first time opened a window to understand the relationship between protein phosphorylation (including serine/threonine phosphorylation) and malignant cell transformation (e.g., development of cancer) [4]. In addition, a growing body of evidence has demonstrated that tyrosine phosphorylation catalyzed by cellular Src and other PTKs expressed in normal cells and tissues regulates a variety of cellular functions such as developmental processes, disorder of normal cell functions, immunological responses, neuronal differentiation and transmission, pathological infection, and senescence. Thus, protein-tyrosine phosphorylation has emerged as a signal transduction mechanism of fundamental importance in all eukaryotic cells and, in some cases, prokaryotic cell behavior [5¨C7]. In the sexual reproduction system, two different kinds of gamete cell: egg and sperm, interact and fuse with each other to accomplish fertilization that gives rise to a newborn [8]. In this fundamental biological event, both egg and sperm undergo a number of biochemical and cell biological reactions that culminate in successful embryogenesis and early development. Especially in
%U http://www.hindawi.com/journals/jst/2012/181560/