TGF-β (56E4) Rabbit mAb #3709

Transforming growth factor-β (TGF-β) proteins belong to the TGF-β superfamily of cytokines that play a critical role in regulating cell proliferation and differentiation, developmental patterning and morphogenesis, and disease pathogenesis (1-3). TGF-β ligands elicit signaling through three cell surface receptors: type I (RI), type II (RII), and type III (RIII) TGF-β receptors. Type I and type II receptors are serine/threonine kinases that form a heteromeric complex following ligand binding to the type II receptor. In response to ligand binding, the type II receptors form a stable complex with the type I receptors, triggering phosphorylation and activation of the type I receptor (4). This results in the recruitment of receptor-mediated SMADs (SMAD2, SMAD3), which are phosphorylated by the type I kinase in an SSXS domain in the C-terminus. This leads to recruitment of the co-SMAD (SMAD4), and subsequent translocation of this heteromeric SMAD complex to the nucleus, where it regulates transcription of target genes (5-7). The type III receptor, also known as betaglycan, is a transmembrane proteoglycan with a large extracellular domain that binds TGF-β with high affinity but lacks a cytoplasmic signaling domain. Expression of the type III receptor can regulate TGF-β signaling through presentation of the ligand to the signaling complex (8).

Three isoforms of TGF-β, designated TGF-β1, TGF-β2 and TGF-β3, are encoded by distinct genes and are expressed in a tissue specific manner (10). Each isoform is synthesized as a larger precursor protein containing a propeptide region that is removed prior to secretion. Mature TGF-β contains two polypeptides linked by disulfide bonds to form a protein of approximately 25 kDa.