AG 490, JAK2/3 inhibitor

Supplementary information

This supplementary information is collated from multiple sources and compiled automatically.

JAK2 and JAK3 are key members of the Janus kinase family with JAK2 often referred to as Janus kinase 2. JAK2 has a molecular mass of approximately 130 kDa and is widely expressed in hematopoietic cells whereas JAK3 weighing about 125 kDa is predominantly found in immune cells such as T and B lymphocytes. These kinases function as intracellular non-receptor tyrosine kinases that transduce cytokine-mediated signals via the JAK-STAT signaling pathway. They possess distinct domains: the JH1 domain responsible for kinase activity and the JH2 domain providing a regulatory role.

Biological function summary

JAK2 and JAK3 transmit signals from various cytokine receptors to modulate important cellular functions like proliferation differentiation and apoptosis. They do not operate in isolation; these kinases are part of large complexes that include specific receptor subunits and downstream signal transducers known as STATs (Signal Transducer and Activator of Transcription proteins). As part of these complexes they ensure the precise transmission of extracellular cytokine signals to the nucleus altering gene expression patterns to affect cellular responses.

Pathways

These kinases have essential roles in the JAK-STAT signaling pathway and the PI3K-AKT pathway. JAK2 and JAK3 activation leads to the phosphorylation of STAT proteins which then dimerize and translocate to the nucleus to modulate gene expression. In these pathways they interact with various proteins like STAT5 and STAT1 that facilitate their signaling roles. Their activity is tightly regulated and their dysregulation can lead to implicating pathological conditions.

JAK2 and JAK3 are closely associated with myeloproliferative disorders and immunodeficiencies. Mutations in JAK2 such as the JAK2 V617F mutation are linked to conditions like polycythemia vera and essential thrombocythemia where unchecked cell proliferation occurs. JAK3 deficiencies or mutations often lead to severe combined immunodeficiency (SCID) affecting immune cell development. These conditions highlight the therapeutic potential of JAK2 inhibitors and JAK3 inhibitors to modulate abnormal kinase activity with agents like AG-490 being notable for their inhibitory effects on JAK2.