Transforming growth factor beta (TGF-β) is a protein that controls proliferation, cellular differentiation, and other functions in most cells. It is a type of cytokine which plays a role in immunity, cancer, heart disease, diabetes, Marfan syndrome, Loeys–Dietz syndrome, Parkinson's disease and AIDS.
TGF-β is a secreted protein that exists in at least three isoforms called TGF-β1, TGF-β2 and TGF-β3. It was also the original name for TGF-β1, which was the founding member of this family. The TGF-β family is part of a superfamily of proteins known as the transforming growth factor beta superfamily, which includes inhibins, activin, anti-müllerian hormone, bone morphogenetic protein, decapentaplegic and Vg-1.
Most tissues have high expression of the gene encoding TGF-β. That contrasts with other anti-inflammatory cytokines such as IL-10, whose expression is minimal in unstimulated tissues and seems to require triggering by commensal or pathogenic flora.
TGF-beta acts as an antiproliferative factor in normal epithelial cells and at early stages of oncogenesis.
Some cells that secrete TGF-β also have receptors for TGF-β. This is known as autocrine signalling. Cancerous cells increase their production of TGF-β, which also acts on surrounding cells.
TGF-beta is secreted by many cell types, including macrophages, in a latent form in which it is complexed with two other polypeptides, latent TGF-beta binding protein (LTBP) and latency-associated peptide (LAP). Serum proteinases such as plasmin catalyze the release of active TGF-beta from the complex. This often occurs on the surface of macrophages where the latent TGF-beta complex is bound to CD36 via its ligand, thrombospondin-1 (TSP-1). Inflammatory stimuli that activate macrophages enhance the release of active TGF-beta by promoting the activation of plasmin. Macrophages can also endocytose IgG-bound latent TGF-beta complexes that are secreted by plasma cells and then release active TGF-beta into the extracellular fluid.
Read more about Transforming Growth Factor Beta: The Structure of TGF-β, Types, TGF-β Activation, TGF-β Latency (latent TGF-β Complex), Integrin-independent TGF-β Activation, Activation By Alpha(V) Containing Integrins, See Also, External Links
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