on 12-11-2015 02:26 PM - edited on 10-15-2021 11:05 AM by AnalyteGuru
Joseph Gault1¤, Mathias Ferber2, Silke Machata3,4, Anne-Flore Imhaus3,4, Christian Malosse1, Arthur Charles-Orszag3,4, Corinne Millien3,4, Guillaume Bouvier2, Benjamin Bardiaux2, Gérard Péhau-Arnaudet5, Kelly Klinge6, Isabelle Podglajen7, Marie Cécile Ploy8, H. Steven Seifert6, Michael Nilges2, Julia Chamot-Rooke1, Guillaume Duménil3,4*
PLoS Pathog. 2015 Sep 14;11(9):e1005162. doi: 10.1371/journal.ppat.1005162. eCollection 2015.
The ability of pathogens to cause disease depends on their aptitude to escape the immune system. Type IV pili are extracellular filamentous virulence factors composed of pilin monomers and frequently expressed by bacterial pathogens. As such they are major targets for the host immune system. In the human pathogen Neisseria meningitidis, strains expressing class I pilins contain a genetic recombination system that promotes variation of the pilin sequence and is thought to aid immune escape. However, numerous hypervirulent clinical isolates express class II pilins that lack this property. This raises the question of how they evade immunity targeting type IV pili. As glycosylation is a possible source of antigenic variation it was investigated using top-down mass spectrometry to provide the highest molecular precision on the modified proteins. Unlike class I pilins that carry a single glycan, we found that class II pilins display up to 5 glycosylation sites per monomer on the pilus surface. Swapping of pilin class and genetic background shows that the pilin primary structure determines multisite glycosylation while the genetic background determines the nature of the glycans. Absence of glycosylation in class II pilins affects pilus biogenesis or enhances pilus dependent aggregation in a strain specific fashion highlighting the extensive functional impact of multisite glycosylation. Finally, molecular modeling shows that glycans cover the surface of class II pilins and strongly decrease antibody access to the polypeptide chain. This strongly supports a model where strains expressing class II pilins evade the immune system by changing their sugar structure rather than pilin primary structure. Overall these results show that sequence invariable class II pilins are cloaked in glycans with extensive functional and immunological consequences.
1 Structural Mass Spectrometry and Proteomics Unit, Institut Pasteur, CNRS UMR 3528, Paris, France 2 Institut Pasteur, UnitÃ© de Bioinformatique Structurale, CNRS UMR 3528, DÃ©partement de Biologie Structurale et Chimie, Paris, France 3 INSERM, U970, Paris Cardiovascular Research Center, Paris, France 4 UniversitÃ© Paris Descartes, FacultÃ© de MÃ©decine Paris Descartes, Paris, France 5 CNRS, UMR3528, Paris, France, 6 Department of Microbiology-Immunology Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America 7 Service de Microbiologie, Assistance Publique-HÃ´pitaux de Paris, HÃ´pital EuropÃ©en Georges-Pompidou, Paris, France 8 INSERM UMR1092, FacultÃ© de MÃ©decine, UniversitÃ© de Limoges, Limoges, France