JAK-STAT signaling pathway

The JAK-STAT signaling pathway transmits information from extracellular chemical signals to the nucleus resulting in DNA transcription and expression of genes involved in immunity, proliferation, differentiation, apoptosis and oncogenesis. The JAK-STAT signalling cascade consists of three main components: a cell surface receptor, a Janus kinase (JAK) and two Signal Transducer and Activator of Transcription (STAT) proteins. Disrupted or dysregulated JAK-STAT functionality can result in immune deficiency syndromes and cancers.

The binding of various ligands, usually cytokines, such as interferon, interleukin, and growth factors to cell surface receptors, activate associated JAKs, increasing their kinase activity. Activated JAKs then phosphorylate tyrosine residues on the receptor, creating binding sites for proteins possessing SH2 domains. SH2 domain containing STATs are recruited to the receptor where they are also tyrosine-phosphorylated by JAKs. These activated STATs form hetero- or homodimers and translocate to the cell nucleus where they induce transcription of target genes. STATs may also be tyrosine-phosphorylated directly by receptor tyrosine kinases, such as the epidermal growth factor receptor, as well as by non-receptor (cytoplasmic) tyrosine kinases such as c-src.

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