Also found in: Acronyms, Wikipedia.
Janus kinase (JAK),
a member of a particular family (JAK) of tyrosine kinases involved in cytokine receptor signaling. Mutations in JAK3 on chromosome 19p cause autosomal recessive severe combined immunodeficiency [MIM*600173]. JAK1 and JAK2 are mapped to the short arms of chromosomes 1 and 9, respectively.
[Janus, Roman god of doorways, depicted with two faces looking in opposite directions]
Janus kinaseAny of a family of four tyrosine kinases—JAK1, JAK2, JAK3 and Tyk2—that associate with cytokine receptors. Once receptors are activated, JAKs phosphorylate STAT transcription factors, initiating the JAK-STAT signalling pathway. JAK family members share a common protein domain, a kinase domain, a regulatory pseudo -kinase domain, a SH2 domain and a FERM domain, this last of which mediates the association of JAK with other enzymes and cytokine receptors.
JAK family associations
• JAK1—Mediates signals from IFN-alpha, beta, gamma and IL2, IL6 receptors.
• JAK2—Transduces signals from single chain, IL3 receptor families and IFN-gamma receptors.
• JAK3—Associates with the IL2 receptor gamma-chain.
• Tyk2—Associates with the IFN1 and IL6, -10, -12 and -23 cytokine receptors.