Signal transduction of cytokine receptors - Structure of receptor and signal transduction mechanism

Growth, differentiation and functions of immune and hematopoietic cells are controlled by multiple cytokines, including interleukins and colony stimulating factors. Cytokines exert their biological effects through binding to cell surface receptors that are associated with one or more members of the JAK family of cytoplasmic tyrosine kinases JAKs). Cytokine receptors form ligand-dependent homo- or hetero- dimerization and in many cases, receptors share common subunits. This partly explains why several cytokines exhibit similar functions. Cytokine-induced receptor dimerization leads to the activation of JAKs, rapid tyrosine phosphorylation of the cytoplasmic domains and subsequent recruitment of various signaling proteins for the receptor complex. Among these proteins are members of the STAT family of transcription factors. Ras-MAP kinase cascade and other signaling pathways are also activated. Now we start to understand the molecular mechanism of cytokine signal transduction and its relationship to diseases.