The Janus family of tyrosine kinases (JAK) includes JAK1, JAK2, JAK3 and Tyk2. This family associates with a variety of cytokine receptors and is activated by ligand binding. Upon ligand binding to cytokine receptors, JAKs phosphorylate themselves and their associated receptors. This provides multiple binding sites for signaling proteins containing SH2 or other phospho-tyrosine-binding domains, including STATs, Shc, insulin receptor substrates and FAK. Thus, JAK kinases provide important links between cytokine/hormone receptors and downstream effector proteins, and efficient study methods are in high demand.


