Janus kinase 1, Janus kinase 2, and Janus kinase 3 (JAK1, JAK2, JAK3)

Janus kinase 1, Janus kinase 2, and Janus kinase 3 (JAK1/2/3) are members of the Janus kinase family of intracellular, non-receptor tyrosine kinases that mediate signal transduction from a variety of cytokine and growth factor receptors through the JAK-STAT pathway. They possess a characteristic domain structure consisting of a FERM domain (receptor binding), SH2 domain (scaffolding and receptor association), pseudokinase (JH2; regulatory), and kinase (JH1) domain (catalytic function)[1][2][3][4][5]. JAK1/2/3 are critical for immune system development, regulation, and hematopoiesis; their dysregulation underlies a range of diseases, making them highly validated therapeutic targets for immunological, hematological, and oncological disorders. Selective or pan-JAK inhibitors are now established therapies in several autoimmune and hematologic diseases[1][2][4].

Other names

JAK1JAK2JAK3Non-receptor tyrosine kinase JAK1/2/3 (less common)

Inhibition of JAK kinase activity, preventing phosphorylation of downstream STAT proteins and blocking cytokine receptor–mediated signal transduction[1][2][4]