1. Recombinant Proteins
  2. Receptor Proteins
  3. Enzyme-linked receptors
  4. Type III RSTKs

Receptor serine/threonine kinases (RSTKs) are transmembrane proteins of the plasma membrane and are characterized by extracellular ligand-binding domains and cytoplasmic kinase domains. RSTKs mediate inhibitory as well as stimulatory signals for growth and differentiation by binding to members of the transforming growth factor-β (TGF-β) superfamily, e.g. TGF-beta and activins. TGF-β family receptors are grouped into three types, type I, type II, and type III. TβRIII functions as a co-receptor to increase ligand binding to TβRII. Once bound to TGF-β, TβRII recruits, binds, and transphosphorylates TβRI, thereby stimulating its protein kinase activity. Activation of TGF-β receptors induces signaling via formation of Smad complexes that are translocated to the nucleus where they act as transcription factors, as well as via non-Smad pathways, including the Erk1/2, JNK and p38 MAP kinase pathways, and the Src tyrosine kinase, phosphatidylinositol 3′-kinase, and Rho GTPases. The type III TGF-β receptor (TβRIII, also known as betaglycan), an 849 aa heparan sulfate proteoglycan, is classically thought to function as a co-receptor, presenting TGF-β superfamily ligands to their respective signaling receptors. It is reported that TβRIII also mediates ligand independent signaling. TβRIII has also been shown to be an important regulator of cell migration, invasion, cell growth, and angiogenesis in both in vitro and in vivo cancer models.