Cytokine Signaling

Cytokines are a category of signaling molecules that are used extensively in cellular communication. They are proteins, peptides, or glycoproteins. The term cytokine encompasses a large and diverse family of polypeptide regulators that are produced widely throughout the body by cells of diverse embryological origin.

Cytokines typically consists of two chains each having extra-cellular Cytokines binding domain and intracytoplasmic domain, which binds member of family protein tyrosine kinases called Janus kinases or JAK kinase. In the absences of cytokine the two chain do not remain associateded.the cytokine binding to the receptors stabilize the hetero dimer and brings together the JAKs that are bound to the cytoplasmic portions of each chain.

JAKS kinases those are able to phosphoralate cytoplasmic tails of the cytokine receptors.

Signal trasduction and transcription or STAT molecules bind to the phosphorated cytokine receptor chains and phosphorated by JAKS.

The addition of phosphate to the STATs enables them to dimerise and migrate to the nuclues,where the directly activate gene transcription.