JAK-STAT signaling pathway is a cytokine-stimulated signal transduction pathway involved in many important biological processes such as cell proliferation, differentiation, apoptosis, and immune regulation. Currently, the research on disease and drug innovation focuses on inflammatory and neoplastic diseases. Compared with other signaling pathways, this signaling pathway is relatively simple. It consists of three major components: tyrosine kinase associated receptor, Janus kinase (JAK) and transcription factor STAT (signal transducer and activator of transcription). The JAK protein family consists of four members: JAK1, JAK2, JAK3, and Tyk2 and six members of the STAT family have now been identified, STAT1-STAT6.
It is worth mentioning that a JAK kinase can participate in the signal transduction process of a variety of cytokines. One cytokine signaling pathway can also activate multiple JAK kinases, but cytokines are selective in activating STAT molecules. For example, IL-4 activates STAT6, whereas IL-12 specifically activates STAT4.