Janus kinase 2 (JAK2) JH2 pseudokinase domain (JAK2 JH2)

Janus kinase 2 (JAK2) is a non-receptor tyrosine kinase essential for signaling through various cytokine and growth factor receptors, including those for erythropoietin and thrombopoietin (UniProt P23458). The protein is characterized by a tandem kinase domain structure consisting of a catalytic JH1 domain and a regulatory JH2 pseudokinase domain (PubMed: 24531476). While the JH2 domain lacks significant catalytic activity, it plays a critical role in autoinhibiting the JH1 domain under basal conditions (PubMed: 24531476). Mutations within the JH2 domain, most notably the V617F substitution, disrupt this autoinhibition, leading to constitutive JAK2 signaling and the development of myeloproliferative neoplasms (MPNs) such as polycythemia vera and essential thrombocythemia (PubMed: 15752323). Traditional JAK inhibitors, such as ruxolitinib, target the ATP-binding site of the JH1 domain, but these often lack selectivity among JAK family members and can cause significant side effects (PubMed: 20554982). Emerging therapeutic strategies focus on the JH2 domain as an allosteric site to achieve greater isoform selectivity and specifically inhibit the mutant form of the enzyme (PubMed: 31152140). By stabilizing the inactive conformation of JAK2, JH2-directed inhibitors offer a promising approach to treating MPNs with potentially fewer off-target effects compared to orthosteric inhibitors.

Other names

Janus homology 2 domain of Janus kinase 2JAK2 pseudokinase domainJAK2 JH2 domainJanus homology 2 domain of JAK2

Allosteric inhibition by binding to the pseudokinase domain to stabilize the autoinhibitory interaction with the catalytic JH1 domain, thereby preventing kinase activation.