Protein-tyrosine kinase 2-beta (PTK2B), also known as focal adhesion kinase 2 (FAK2), proline-rich tyrosine kinase 2 (PYK2), related adhesion focal tyrosine kinase (RAFTK), or calcium-dependent tyrosine kinase (CADTK), is a non-receptor protein-tyrosine kinase that is structurally similar to FAK []. FAK and PYK2 may be involved in several overlapping signalling pathways [, ]. FAK is expressed ubiquitously, whereas PYK2 expression is restricted to the endothelium, central nervous system, and hematopoietic lineages. PYK2 contains a central tyrosine kinase domain flanked by an N-terminal FERM domain, which mediates the binding of PYK2 to multiple proteins, and a C-terminal focal adhesion targeting (FAT) domain []. PYK2 is sensitive to intracellular Ca+ signalling and G-protein-coupled receptors [, ].PYK2 plays a critical role in the migration of multiple cell lineages induced by growth factor, cytokine and integrin receptors. PYK2 alters the migratory ability of these cells by directly phosphorylating proteins that link focal adhesions to the actin cytoskeleton. It also recruits Src family kinases and other signalling proteins to focal adhesions, and directly alters actin cytoskeleton rearrangement via regulating the activity of Rac [, , ]. It has roles in T-cells [], macrophages [], bone formation [, , ],and vascular function [].
