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A small GTP-binding protein, Rho, associates with the platelet-derived growth factor type-beta receptor upon ligand
M Zubiaur1, J Sancho, C Terhorst
1Cancer Research Center, Boston University School of Medicine, Massachusetts 02118, USA.
Abstract:
Ligand binding to the platelet-derived growth factor (PDGF) receptor initiates a complex and diverging cascade of signaling pathways. GTP-binding proteins with intrinsic GTPase activity (G-proteins) frequently link cell surface receptors to intracellular signaling pathways, but no close associations of the PDGF receptor and any small G-proteins, nor any such associations activated by ligand binding to the receptor have been previously reported. We demonstrate that a small GTP-binding protein binds specifically to the murine and human PDGF type-beta receptor. In response to PDGF-BB stimulation, there is an increase in the amount of labeled small G-protein associated with the PDGF type-beta receptor. The GTP-binding protein did not undergo ligand-induced association with a mutant receptor protein that was unable to bind ATP. Proteolytic cleavage analysis, together with two-dimensional separation techniques, identified the small G-protein specifically associating with the PDGF type-beta receptor after ligand binding as a member of the Rho family. This was confirmed by demonstration that the small G-protein coimmunoprecipitated by the anti-PDGF receptor antibody was a substrate for the ADP-ribosyltransferase C3 exoenzyme. Thus, the PDGF type-beta receptor may form a complex with one or more small G-proteins upon binding PDGF-BB, and the Rho small G-protein is likely to be an important component of the proteins making up the multimeric signaling complex of the PDGF type-beta receptor.
Insights
Platelet-derived growth factor (PDGF) receptor binding activates Rho family GTP-binding proteins (G-proteins). This study identifies a novel association between the PDGF type-beta receptor and Rho G-proteins, crucial for PDGF signaling.
Area of Science:
- Cellular signaling
- Molecular biology
- Receptor tyrosine kinases
Background:
- Platelet-derived growth factor (PDGF) receptor activation initiates complex intracellular signaling pathways.
- Small GTP-binding proteins (G-proteins) are known mediators of receptor signaling, but their direct association with the PDGF receptor was previously unestablished.
Purpose of the Study:
- To investigate the potential association between the PDGF receptor and small G-proteins.
- To identify specific G-proteins that interact with the PDGF receptor upon ligand binding.
Main Methods:
- Demonstration of specific binding of a small G-protein to murine and human PDGF type-beta receptor.
- Assessment of ligand-induced association using labeled small G-proteins and a mutant PDGF receptor.
- Identification of the associated small G-protein using proteolytic cleavage and two-dimensional separation.
- Confirmation of Rho family G-protein identity via C3 exoenzyme ADP-ribosylation.
Main Results:
- A small GTP-binding protein specifically binds to the PDGF type-beta receptor.
- PDGF-BB stimulation increases the association of the small G-protein with the PDGF type-beta receptor.
- The identified small G-protein belongs to the Rho family and is a substrate for C3 exoenzyme.
Conclusions:
- The PDGF type-beta receptor forms a complex with small G-proteins upon PDGF-BB binding.
- Rho family small G-proteins are likely integral components of the PDGF type-beta receptor signaling complex.