Cooperative assembly of TGF-beta superfamily signaling complexes is mediated by two disparate mechanisms and distinct modes of receptor binding.Groppe, J., Hinck, C.S., Samavarchi-Tehrani, P., Zubieta, C., Schuermann, J.P., Taylor, A.B., Schwarz, P.M., Wrana, J.L., Hinck, A.P.
(2008) Mol Cell 29: 157-168
- PubMed: 18243111
- DOI: https://doi.org/10.1016/j.molcel.2007.11.039
- Primary Citation of Related Structures:
- PubMed 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.
Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229, USA. email@example.com