Betaglycan presents ligand to the TGFβ signaling receptor

Abstract Transforming growth factor β (TGFβ) signals through a heteromeric protein kinase receptor that has a limited ability to bind ligand. This limitation is overcome by the action of betaglycan (TGFβ type III receptor), a separate TGFβ-binding membrane protein of previously unknown function. Betaglycan presents TGFβ directly to the kinase subunit of the signaling receptor, forming a high affinity ternary complex. Membrane betaglycan increases TGFβ binding to the signaling receptor, enhances cell responsiveness to TGFβ, and eliminates marked biological differences between TGFβ isoforms. Thus, betaglycan is a direct regulator of TGFβ access to the signaling receptors.