Janus kinase (collectively refers to the family; individual members include Janus kinase 1, Janus kinase 2, Janus kinase 3, and Tyrosine kinase 2) (JAK (commonly used for the family and for individual kinases such as JAK1, JAK2, JAK3, TYK2))

Janus kinases are a family of intracellular non-receptor tyrosine kinases (JAK1, JAK2, JAK3, TYK2) critically involved in transmitting signals from cytokine receptors through the JAK-STAT pathway[7][1][4]. Upon cytokine binding to a cell-surface receptor, JAKs activated by receptor oligomerization phosphorylate the receptor, creating docking sites for STAT proteins which translocate to the nucleus to modulate gene expression[1][6][4]. JAKs are vital regulators of immune response, cell growth, differentiation, and homeostasis. Disruption or mutation of JAKs leads to a variety of diseases, and pharmacological inhibition is an established therapeutic strategy in conditions such as rheumatoid arthritis, psoriasis, and certain hematologic malignancies[5][8]. JAK inhibitors are widely used and under active development for multiple indications, but long-term safety profiles continue to be evaluated given their effects on immune and hematopoietic systems[4][8][5].

Other names

JAKsJanus kinasesJust Another Kinase (historical)JAK1JAK2JAK3TYK2

Inhibition of JAK kinase activity, blocking phosphorylation of cytokine receptors - Suppression of downstream STAT activation and nuclear translocation - Modulation of immune and inflammatory responses by reducing cytokine-driven signaling