Molecular Basis of Assembly and Activation of Complement Component C1 in Complex with Immunoglobulin G1 and Antigen
| Autor: | Piet Gros, Rob N. de Jong, Janine Schuurman, Paul W. H. I. Parren, Ewald T. J. van den Bremer, Albert J. R. Heck, Deniz Ugurlar, Aran F. Labrijn, Frank J. Beurskens, Guanbo Wang |
|---|---|
| Rok vydání: | 2015 |
| Předmět: |
0301 basic medicine
Glycosylation Complement factor I Antigen-Antibody Reactions 03 medical and health sciences Classical complement pathway Immunoglobulin Fab Fragments 0302 clinical medicine Tandem Mass Spectrometry Cell Line Tumor Humans Antigens Molecular Biology Complement Activation Complement component 2 biology CD46 Protein Stability Complement C1q Cell Biology Molecular biology Complement system Cell biology 030104 developmental biology Factor H Immunoglobulin G Mutation biology.protein Chromatography Gel Binding Sites Antibody Complement membrane attack complex 030215 immunology Complement control protein Protein Binding |
| Zdroj: | Molecular cell. 63(1) |
| ISSN: | 1097-4164 |
| Popis: | The classical complement pathway contributes to the natural immune defense against pathogens and tumors. IgG antibodies can assemble at the cell surface into hexamers via Fc:Fc interactions, which recruit complement component C1q and induce complement activation. Biophysical characterization of the C1:IgG complex has remained elusive primarily due to the low affinity of IgG-C1q binding. Using IgG variants that dynamically form hexamers efficient in C1q binding and complement activation, we could assess C1q binding in solution by native mass spectrometry and size-exclusion chromatography. Fc-domain deglycosylation, described to abrogate complement activation, affected IgG hexamerization and C1q binding. Strikingly, antigen binding by IgG hexamers or deletion of the Fab arms substantially potentiated complement initiation, suggesting that Fab-mediated effects impact downstream Fc-mediated events. Finally, we characterized a reconstituted 2,045.3 ± 0.4-kDa complex of intact C1 bound to antigen-saturated IgG hexamer by native mass spectrometry, providing a clear visualization of a complete complement initiation complex. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|