Janus kinase 1 and Janus kinase 3 (JAK1 and JAK3)

Janus kinase 1 (JAK1) and Janus kinase 3 (JAK3) are intracellular, non-receptor tyrosine kinases that play essential roles in cytokine-mediated signal transduction via the JAK-STAT pathway. JAK1 is ubiquitously expressed and is involved in signaling for a wide range of cytokines, impacting interferon response, immunity, and hematopoiesis. JAK3 expression is more restricted to hematopoietic cells and is critical for signaling through type I cytokine receptors that use the common gamma chain, essential for lymphocyte development and function. Both kinases are important therapeutic targets in a range of inflammatory and autoimmune diseases, as well as some cancers. Inhibitors of JAK1 and JAK3 (such as tofacitinib) are approved for use in conditions like rheumatoid arthritis and psoriasis but have notable safety concerns due to their key biological roles and impact on immune homeostasis. For structured databases, Janus kinase 1 and Janus kinase 3 should be entered as separate targets due to differences in expression, signaling pathways, pharmacology, and disease associations. Combining both in a single entry is not standard and may lead to loss of essential detail.

Other names

JAK1JAK3Janus kinase family (when referring to all four JAKs: JAK1, JAK2, JAK3, TYK2)

Inhibition of tyrosine kinase activity to block JAK-STAT cytokine signaling, thus suppressing immune and inflammatory responses