Transforming growth factor beta 1 or TGF-β1 is a polypeptide member of the transforming growth factor beta superfamily of cytokines. It is a secreted protein that performs many cellular functions, including the control of cell growth, cell proliferation, cell differentiation, and apoptosis. The transforming growth factor beta-1 is synthesized as precursor consisting of the latency-associated peptide (LAP, 249 aa) and the transforming growth factor beta 1 (112 aa). The precursor is also named small latend complex (SLC) or latent TGF-ß1. The precursor proprotein is cleaved in the Golgi apparatus by Furin, but the disulfide-linked homodimers of LAP and TGF-beta 1 remain non‑covalently associated after secretion. TGF-ß1 activation from latency is controlled both spatially and temporally, by multiple pathways that include actions of proteases such as plasmin and MMP9, and/or by thrombospondin 1 or selected integrins. Once activated following release of LAP, TGF-beta-1 acts by binding to TGF-beta receptors (TGFBR1 and TGFBR2), which transduce signals. Mutations within the LAP are associated with Camurati-Engelmann disease, a rare sclerosing bone dysplasia characterized by inappropriate presence of active TGF-beta 1.
