IL-9 (Interleukin-9) is a TH2-type cytokine first described in the mouse as a potent T-Cell and mast cell growth factor. IL-9 has been reported to be a T-Cell derived cytokine with various effects on a variety of cell types associated with allergic inflam ...mation. IL-9 has been shown to stimulate the proliferation of activated T-Cells, enhance the production of IgE from B-Cells, and promote the proliferation and differentiation of mast cells and hematopoietic progenitors. IL-9 is a member of the 4-helix bundle cytokine family. Human IL-9 consists of a 14kDa glycoprotein whose mature form is composed of 144 amino acids along with a signal sequence of 18 amino acids. The IL-9 protein contains a high proportion of cationic amino acid residues, 10 cysteines and has 4 N-linked glycosylation sites. The human IL-9 gene has been shown to reside within the TH2 cytokine cluster in the region q31-35 on chromosome-5. IL-9 gene is composed of five exons and four introns over approximately 4 kb. IL-9 exerts its effects through a receptor that consists of two chains, the IL-9RAlpha (IL-9-specific Alpha chain of IL-9 Receptor) associated with Gamma chain. The human IL-9R gene consists of 10 exons spread over approximately 13.7 kb of DNA. The receptor is expressed in membrane-bound and soluble forms. Upon IL-9 binding, the IL-9R associates with its co-receptor protein called GammaC. This induces the phosphorylation of the JAK1 (Janus Kinase-1) and JAK3 (Janus Kinase-3) tyrosine kinases, which are associated with IL-9R and GAlpha-C, respectively. A single tyrosine residue of the IL-9R is then phosphorylated and acts as a docking site for 3 transcription factors of the STAT family, which become phosphorylated and migrate to the nucleus, where they activate the transcription of a number of genes.
View More... View Less...