Janus kinase (JAK) signaling pathway (JAK-STAT pathway)

The Janus kinase–signal transducer and activator of transcription (JAK–STAT) signaling pathway mediates cellular responses to cytokines such as interferons and interleukins. Upon cytokine binding to transmembrane receptors associated with Janus kinases (Jaks), these enzymes become activated through transphosphorylation. Activated Jaks then phosphorylate tyrosine residues on the receptors themselves as well as on recruited STAT proteins. Phosphorylated STAT proteins dimerize via their SH2 domains and translocate into the nucleus where they regulate gene expression involved in immunity, cell growth/apoptosis/differentiation/proliferation processes. This highly conserved mechanism plays critical roles in immune regulation but also contributes pathologically when dysregulated—such as in cancer or autoimmune diseases. Negative regulators such as SOCS proteins suppress excessive activity by inhibiting Jak function while PIAS proteins block DNA binding by activated Stat dimers. Protein tyrosine phosphatases like SHP-1 remove phosphate groups from Jak/Stat complexes further modulating activity. Therapeutically targeting this cascade has led development multiple small-molecule inhibitors effective against inflammatory conditions malignancies where aberrant Jak/Stat activity drives pathogenesis.

Other names

Janus kinase-signal transducer and activator of transcription pathwayJAK/STAT signaling cascadeJAK-STAT cascadecytokine receptor-mediated signal transduction

Inhibition of Janus kinases prevents phosphorylation and activation of STAT proteins. Blocking cytokine-induced signal transduction reduces immune cell activation and inflammatory responses. Suppression of aberrant cell proliferation in cancer.