Interleukin 9 and its receptor: an overview of structure and function.
Interleukin-9 (IL-9) is a multifunctional cytokine produced by activated TH2 clones in vitro and during TH2-like T cell responses in vivo. Although IL-9 was initially described as a T cell growth factor, its role in T cell responses is still unclear. While freshly isolated normal T cells do not respond to IL-9, this cytokine induces the proliferation of murine T cell lymphomas in vitro, and in vivo overexpression of IL-9 results in the development of thymic lymphomas. In the human, the existence of an IL-9 mediated autocrine loop has been suggested for some malignancies such as Hodgkin's disease. Various observations indicate that IL-9 is actively involved in mast cells responses by inducing the proliferation and differentiation of these cells. Other potential biological targets for IL-9 include B lymphocytes, and hematopoietic progenitors, for which higher responses were observed with foetal or transformed cells as compared to normal adult progenitors. The IL-9 receptor is a member of the hemopoietin receptor superfamily and interacts with the gamma chain of the IL-2 receptor for signaling. Signal transduction studies have stressed the role of the Jak-STAT pathway in various IL-9 bioactivities, whereas the 4PS/IRS2 adaptor protein might also play a significant role in IL-9 signaling.
Demoulin
J B
JB
Ludwig Institute for Cancer Research and Experimental Medicine Unit, Catholic University of Louvain, Brussels, Belgium.
Renauld
J C
JC
D000818:Animals; D006801:Humans; D016906:Interleukin-9 / Q000737:chemistry / Q000502:physiology; D051379:Mice; D015394:Molecular Structure; D018123:Receptors, Interleukin / Q000737:chemistry / Q000502:physiology; D053651:Receptors, Interleukin-9
C508045:IL9R protein, human; D016906:Interleukin-9; D018123:Receptors, Interleukin; D053651:Receptors, Interleukin-9