Transforming growth factor beta (TGFò) receptors are single pass serine/threonine kinase receptors that belong to TGFò receptor family. They exist in several different isoforms that can be homo- or heterodimeric. The number of characterized ligands in the TGFò superfamily far exceeds the number of known receptors, suggesting the promiscuity that exists between the ligand and receptor interactions.
TGFò is a growth factor and cytokine involved in paracrine signalling and can be found in many different tissue types, including brain, heart, kidney, liver, bone, and testes. Over-expression of TGFò can induce renal fibrosis, causing kidney disease, as well as diabetes, and ultimately end-stage renal disease. Recent developments have found that, using certain types of protein antagonists against TGFò receptors, can halt and in some cases reverse the effects of renal fibrosis.
Three TGFò superfamily receptors specific for TGFò, the TGFò receptors, can be distinguished by their structural and functional properties. TGFòR1 (ALK5) and TGFòR2 have similar ligand-binding affinities and can be distinguished from each other only by peptide mapping. Both TGFòR1 and TGFòR2 have a high affinity for TGFò1 and low affinity for TGFò2. TGFòR3 (ò-glycan) has a high affinity for both homodimeric TGFò1 and TGFò2 and in addition the heterodimer TGF-ò1.2. The TGFò receptors also bind TGFò3.