PhosphoSens JAK2 (JH1JH2) Protein Kinase Assays, Substrates & Recombinant Enzymes

JAK2 (Janus Kinase 2) is a non-receptor tyrosine kinase belonging to the JAK family, which includes JAK1, JAK2, JAK3, and TYK2. JAK2 is constitutively associated with cytokine receptors lacking intrinsic kinase activity, including receptors for erythropoietin, thrombopoietin, growth hormone, and various interleukins. Upon cytokine binding, receptor dimerization triggers JAK2 transphosphorylation at Y1007/Y1008 within the activation loop, unleashing catalytic activity. Activated JAK2 phosphorylates receptor tyrosines that recruit STAT proteins (particularly STAT3 and STAT5), which dimerize, translocate to the nucleus, and drive transcription of genes governing proliferation, survival, and differentiation. The gain-of-function V617F mutation in the pseudokinase JH2 domain constitutively activates JAK2 and is found in over 95% of polycythemia vera cases and approximately 50% of essential thrombocythemia and myelofibrosis cases. This mutation makes JAK2 one of the most validated oncology targets in myeloproliferative neoplasms, and its role in cytokine signaling also implicates it in inflammatory diseases.