The Tec family of cytoplasmic tyrosine kinases: mammalian Btk, Bmx, Itk, Tec, Txk and homologs in other species

Cytoplasmic protein-tyrosine kinases (PTKs) are enzymes involved in transdu cing a vast number of signals in metazoans, The importance of the Tec famil y of kinases was immediately recognized when, in 1993, mutations in the gen e encoding Bruton's tyrosine kinase (Btk) were reported to cause the human disease X-linked agammaglobulinemia (XLA).((1,2)) Since then, additional ki nases belonging to this family have been isolated, and the availability of full genome sequences allows identification of all members in selected spec ies enabling phylogenetic considerations. Tec kinases are endowed with Plec kstrin homology (PH) and Tec homology (TH) domains and are involved in dive rse biological processes related to the control of survival and differentia tion fate, Membrane translocation resulting in the activation of Tec kinase s with subsequent Ca2+ release seems to be a general feature, However, nucl ear translocation may also be of importance, the purpose of this essay is t o characterize members of the Tec family and discuss their involvement in s ignaling. The three-dimensional structure, expression pattern and evolution ary aspects will also be considered. (C) 2001 John Wiley & Sons, Inc.