Janus kinase (family) (JAK (family))

The Janus kinase (JAK) family includes four intracellular, non-receptor tyrosine kinases—JAK1, JAK2, JAK3, and TYK2—which are key mediators of cytokine signaling via the JAK-STAT pathway[1][4][5]. They associate constitutively with type I and type II cytokine receptors, which lack intrinsic kinase activity, and become activated following cytokine binding. Activated JAKs phosphorylate receptor tyrosine residues, creating docking sites for STAT transcription factors, which are then phosphorylated, dimerize, and translocate to the nucleus to modulate gene expression. JAK kinases are essential in immune cell function, hematopoiesis, and inflammatory signaling. Genetic mutations and dysregulation of JAKs are implicated in a wide range of diseases, including cancers, immunodeficiencies, and inflammatory conditions. All approved JAK inhibitors target one or more members of this family and are used clinically in autoimmune and hematological diseases[1][4][6][7]. Because "Janus kinase family member" is imprecise, structured data should normally specify which of JAK1, JAK2, JAK3, or TYK2 is meant, as each has distinct biological roles and pharmacological relevance.

Other names

JAKJust Another KinaseJanus kinasesJaksTyrosine-protein kinase JAKTyrosine kinase 2 (for TYK2)

Inhibition of tyrosine kinase activity, blocking phosphorylation of STAT proteins, and thereby suppressing downstream cytokine signaling (including immune and inflammatory pathways)