Tyrosine kinases

Function

Tyrosine kinases function in a variety of processes, pathways, and actions, and are responsible for key events in the body. The receptor tyrosine kinases function in transmembrane signaling, whereas tyrosine kinases within the cell function in signal transduction to the nucleus. Tyrosine kinase activity in the nucleus involves cell-cycle control and properties of transcription factors. In this way, in fact, tyrosine kinase activity is involved in mitogenesis, or the induction of mitosis in a cell; proteins in the cytosol and proteins in the nucleus are phosphorylated at tyrosine residues during this process. Cellular growth and reproduction may rely to some degree on tyrosine kinase. Tyrosine kinase function has been observed in the nuclear matrix, which comprises not the chromatin but rather the nuclear envelope and a “fibrous web” that serves to physically stabilize DNA. To be specific, Lyn, a type of kinase in the Src family that was identified in the nuclear matrix, appears to control the cell cycle. Src family tyrosine kinases are closely related but demonstrate a wide variety of functionality. Roles or expressions of Src family tyrosine kinases vary significantly according to cell type, as well as during cell growth and differentiation. Lyn and Src family tyrosine kinases in general have been known to function in signal transduction pathways. There is evidence that Lyn is localized at the cell membrane; Lyn is associated both physically and functionally with a variety of receptor molecules.