What is TGF β?
The transforming growth factor beta (TGF-β) superfamily is a family of proteins that is involved in regulating and mediating processes at the cellular level, including cell proliferation, differentiation, motility, adhesion and apoptosis, as well as processes at the tissue and organism level, including development, wound healing, fibrosis and angiogenesis. The TGF-β superfamily consists of ligands and receptors that all signal, at least in part, through well characterized downstream mediators termed the Smads.
TGF beta ligands
The TGF-β1 ligand is the founding member of the TGF-β superfamily of proteins that includes TGF-βs, bone morphogenetic proteins (BMPs), activins, growth differentiation factors (GDFs), activin/inhibin subfamily, Glial-derived Neurotrophic Factors (GDNFs) and Müllerian inhibiting substance (MIS). TGF-β1 and all other TGF-β superfamily ligands are dimers that are held together by three disulfide bonds that are part of a characteristic structure called a cysteine knot. Secreted TGF-β is a latent complex that is composed of the TGF-β dimer associated with the latency associated peptide (LAP) and the latent TGF-β binding protein (LTBP). The latent complex is proteolytically cleaved in the extracellular space resulting in the release of the TGF-β dimer, allowing TGF-β to bind cell surface receptors. The cell surface TGF-β superfamily receptors are classified as either type I receptors, type II receptors, or co-receptors.