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Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
Published on: May 26, 2011
Complement component 5a receptor oligomerization and homologous receptor down-regulation.
Marie-Josèphe Rabiet1, Emilie Huet, François Boulay
1Laboratoire Biochimie et Biophysique des Systèmes Intégrés, Grenoble F-38054, France. marie-josephe.rabiet@cea.fr
The Journal of Biological Chemistry
|September 6, 2008
Summary
G-protein-coupled receptors (GPCRs) like C5aR form dimers. Stimulation of one C5aR dimer partner leads to the internalization of both, crucial for regulating C5aR function in disease.
Area of Science:
- Cellular Biology
- Molecular Pharmacology
- Immunology
Background:
- Most G-protein-coupled receptors (GPCRs) form dimers, which are critical for their signaling and trafficking.
- Cellular responses to complement C5a receptor (C5aR) involve desensitization and internalization, processes tightly regulated by the receptor.
- Understanding GPCR dimerization is key to comprehending receptor regulation and function.
Purpose of the Study:
- To investigate the role of C5aR dimerization in receptor regulation, specifically desensitization and internalization.
- To determine if receptor dimerization is necessary for C5aR internalization upon C5a stimulation.
- To explore the impact of receptor binding and phosphorylation status on C5aR dimerization and co-internalization.
Main Methods:
- Generation of modified C5aR mutants: an NH(2)-terminally modified mutant unable to bind C5a and a phosphorylation-deficient mutant.
- Co-expression of wild-type C5aR with either the unliganded or phosphorylation-deficient mutant in cells.
- Stimulation with C5a and subsequent analysis of receptor internalization and phosphorylation using techniques like (32)P labeling.
Main Results:
- C5aR dimerization occurs independently of the NH(2) terminus and COOH-terminal phosphorylation sites.
- Individual expression of C5aR mutants (unliganded or phosphorylation-deficient) did not lead to internalization upon C5a stimulation.
- Co-expression studies revealed that C5a stimulation induced co-internalization of wild-type C5aR with either unliganded or phosphorylation-deficient mutants.
- Stimulation and phosphorylation of one C5aR monomer were sufficient to drive the internalization of the entire dimer.
Conclusions:
- C5aR dimerization is essential for its proper regulation, particularly for internalization upon ligand binding.
- The stimulation of one receptor monomer within a dimer triggers the internalization of the complex, irrespective of the other monomer's binding or phosphorylation status.
- GPCR dimer formation and function are critical for receptor down-regulation, with implications for understanding and treating pathological conditions involving C5aR.
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