Non-receptor tyrosine kinase involved in various processes such as cell growth, development, or differentiation. Mediates essential signaling events in both innate and adaptive immunity and plays a crucial role in hematopoiesis during T-cells development. In the cytoplasm, plays a pivotal role in signal transduction via its association with type I receptors sharing the common subunit gamma such as IL2R, IL4R, IL7R, IL9R, IL15R and IL21R. Following ligand binding to cell surface receptors, phosphorylates specific tyrosine residues on the cytoplasmic tails of the receptor, creating docking sites for STATs proteins. Subsequently, phosphorylates the STATs proteins once they are recruited to the receptor. Phosphorylated STATs then form homodimer or heterodimers and translocate to the nucleus to activate gene transcription. For example, upon IL2R activation by IL2, JAK1 and JAK3 molecules bind to IL2R beta (IL2RB) and gamma chain (IL2RG) subunits inducing the tyrosine phosphorylation of both receptor subunits on their cytoplasmic domain. Then, STAT5A AND STAT5B are recruited, phosphorylated and activated by JAK1 and JAK3. Once activated, dimerized STAT5 translocates to the nucleus and promotes the transcription of specific target genes in a cytokine-specific fashion. Belongs to the protein kinase superfamily. Tyr protein kinase family. JAK subfamily. In NK cells and an NK-like cell line but not in resting T-cells or in other tissues. The S-form is more commonly seen in hematopoietic lines, whereas the B-form is detected in cells both of hematopoietic and epithelial origins. 3 alternatively spliced human isoforms have been reported. Note: This description may include information from UniProtKB.
Protein type: EC 126.96.36.199; JakA family; Kinase, protein; Protein kinase, TK; Protein kinase, tyrosine (non-receptor); TK group
Molecular Function: ATP binding; non-membrane spanning protein tyrosine kinase activity; protein phosphatase binding; protein tyrosine kinase activity
Biological Process: adaptive immune response; B cell differentiation; cellular response to cytokine stimulus; cytokine-mediated signaling pathway; enzyme linked receptor protein signaling pathway; erythrocyte differentiation; innate immune response; interleukin-4-mediated signaling pathway; intracellular signal transduction; negative regulation of complement-dependent cytotoxicity; negative regulation of dendritic cell cytokine production; negative regulation of FasL biosynthetic process; negative regulation of interleukin-10 production; negative regulation of interleukin-12 production; negative regulation of T cell activation; negative regulation of T-helper 1 cell differentiation; negative regulation of thymocyte apoptotic process; peptidyl-tyrosine phosphorylation; positive regulation of activated T cell proliferation; positive regulation of calcium ion transport; positive regulation of cytosolic calcium ion concentration; positive regulation of dendritic cell apoptotic process; positive regulation of extrinsic apoptotic signaling pathway in absence of ligand; positive regulation of nitric-oxide synthase biosynthetic process; positive regulation of T cell proliferation; positive regulation of transcription by RNA polymerase II; regulation of T cell apoptotic process; response to interleukin-4; T cell homeostasis; tyrosine phosphorylation of STAT protein