PMID: 18243111 , Related PDB id: 2PJY

Authors:

Groppe J, Hinck CS, Samavarchi-Tehrani P, Zubieta C, Schuermann JP, Taylor AB, Schwarz PM, Wrana JL, Hinck AP

Title:

Cooperative assembly of TGF-beta superfamily signaling complexes is mediated by two disparate mechanisms and distinct modes of receptor binding.

Journal:

Mol Cell. 2008 Feb 1;29(2):157-68.

Abstract:

Dimeric ligands of the transforming growth factor-beta (TGF-beta) superfamily signal across cell membranes in a distinctive manner by assembling heterotetrameric complexes of structurally related serine/threonine-kinase receptor pairs. Unlike complexes of the bone morphogenetic protein (BMP) branch that apparently form due to avidity from membrane localization, TGF-beta complexes assemble cooperatively through recruitment of the low-affinity (type I) receptor by the ligand-bound high-affinity (type II) pair. Here we report the crystal structure of TGF-beta3 in complex with the extracellular domains of both pairs of receptors, revealing that the type I docks and becomes tethered via unique extensions at a composite ligand-type II interface. Disrupting the receptor-receptor interactions conferred by these extensions abolishes assembly of the signaling complex and signal transduction (Smad activation). Although structurally similar, BMP and TGF-beta receptors bind in dramatically different modes, mediating graded and switch-like assembly mechanisms that may have coevolved with branch-specific groups of cytoplasmic effectors.