Zeta Chain Associated Protein Kinase 70kDa (zAP70)

ZAP70 encodes an enzyme belonging to the protein tyrosine kinase family, and it plays a role in T-cell development and lymphocyte activation. This enzyme, which is phosphorylated on tyrosine residues upon T-cell antigen receptor (TCR) stimulation, functions in the initial step of TCR-mediated signal transduction in combination with the Src family kinases, Lck and Fyn. This enzyme is also essential for thymocyte development. Mutations in this gene cause selective T-cell defect, a severe combined immunodeficiency disease characterized by a selective absence of CD8-positive T-cells. Two transcript variants that encode different isoforms have been found for this gene.ZAP70 associates with the zeta chain and undergoes tyrosine phosphorylation following TCR stimulation. The ZAP70 gene is expressed in T- and natural killer cells.