PYK2, a 116 kD proline-rich non-receptor tyrosine kinase also known as FAK2 or PTK2B, is ubiquitously expressed in the cytoplasm. PYK2 is activated in response to integrin ligation, CD3 or TCR ligation, growth factors, cytokines, chemokines, and cellular stress. This kinase has been shown to regulate ion channels, vesicular transport, participate in T- and B-cell receptor signaling, and play a role in apoptosis. PYK2 is activated through phosphorylation following increased intracellular calcium and can be dephosphorylated by calcitonin, and protein tyrosine phosphatase (non-receptor) type 12 to decrease kinase activity. PYK2 has been shown to interact with Grb2, SHP1, integrin beta3, Fyn, c-Src, talin, paxillin, Vav-1, Lyn, and HIC5. The Poly6053 antibody recognizes the N-terminal region of human, mouse, and ratPYK2 and has been shown to be useful for Western blotting.