BMPR2

Bone morphogenetic protein receptor type II or BMPR2 is a serine/threonine receptor kinase encoded by the BMPR2 gene. It binds bone morphogenetic proteins, members of the TGF beta superfamily of ligands, which are involved in paracrine signaling. BMPs are involved in a host of cellular functions including osteogenesis, cell growth and cell differentiation. Signaling in the BMP pathway begins with the binding of a BMP to the type II receptor. This causes the recruitment of a BMP type I receptor, which the type II receptor phosphorylates. The type I receptor phosphorylates an R-SMAD, a transcriptional regulator.

== Function == Unlike the TGFβ type II receptor, which has a high affinity for TGF-β1, BMPR2 does not have a high affinity for BMP-2, BMP-7 and BMP-4, unless it is co-expressed with a type I BMP receptor. On ligand binding, a receptor complex is formed, consisting of two type II and two type I transmembrane serine/threonine kinases. Type II receptors phosphorylate and activate type I receptors which autophosphorylate, then bind and activate SMAD transcriptional regulators. They bind to BMP-7, BMP-2 and, less efficiently, BMP-4. Binding is weak but enhanced by the presence of type I receptors for BMPs. In TGF beta signaling all of the receptors exist in homodimers before ligand binding. In the case of BMP receptors only a small fraction of the receptors exist in homomeric forms before ligand binding. Once a ligand has bound to a receptor, the amount of homomeric receptor oligomers increase, suggesting that the equilibrium shifts towards the homodimeric form. The low affinity for ligands suggests that BMPR2 may differ from other type II TGF beta receptors in that the ligand may bind the type I receptor first.