Promiscuity and specificity in BMP receptor activation

Bone Morphogenetic Proteins (BMPs), together with Transforming Growth Factor (TGF)-beta and Activins/Inhibins constitute the TGF-beta superfamily of ligands. This superfamily is formed by more than 30 structurally related secreted proteins. Since TGF-beta members act as morphogens, either a strict relation between a particular ligand to a distinct cellular receptor and/or temporospatial expression patterns of ligands and receptors is expected. Instead, only a limited number of receptors exist implicating promiscuous interactions of ligands and receptors. Furthermore, in complex tissues a multitude of different ligands can be found, which signal via overlapping subsets of receptors. This raises the intriguing question how concerted interactions of different ligands and receptors generate highly specific cellular signals, which are required during development and tissue homeostasis. (C) 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.