title: Identification of OprF as a complement component C3 binding acceptor molecule on the surface of Pseudomonas aeruginosa.
abstract: Pseudomonas aeruginosa is a versatile opportunistic pathogen that can cause devastating persistent infections. Complement is a highly conserved pathway of the innate immune system, and its role in the first line of defense against pathogens is widely appreciated. One of the earliest events in the complement cascade is the conversion of C3 to C3a and C3b, the latter typically binds to one or more acceptor molecules on the pathogen surface. We previously demonstrated that complement C3b binding acceptors exist on the P. aeruginosa surface. In the current study, we utilized either C3 polyclonal or C3b monoclonal antibodies in a far-Western technique followed by mass spectroscopy to identify the C3b acceptor molecule(s) on the P. aeruginosa surface. Our data provide evidence that OprF (an outer membrane porin, highly conserved in the Pseudomonadaceae) binds C3b. An oprF-deficient P. aeruginosa strain exhibits reduced C3 deposition compared to the wild type. We observed reduced internalization of oprF-deficient bacteria by neutrophils after opsonization compared with wild-type P. aeruginosa. Heterologous expression of OprF significantly enhanced C3b binding and increased serum-mediated bactericidal effects in complement-susceptible Escherichia coli. Furthermore, the predicted secondary structure of the C-terminal, surface-exposed region of OprF has high structural identity to the OmpA domain of several other Gram-negative bacteria, one of which is known to bind C3b. Therefore, these findings provide new insights into the biology of complement interactions with P. aeruginosa and other Gram-negative bacteria.
authors.affiliation: Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, USA Center for Microbial Interface Biology, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Meenu
authors.initials: M
authors.lastname: Mishra
authors.affiliation: Department of Internal Medicine, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Adam
authors.initials: A
authors.lastname: Ressler
authors.affiliation: Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, USA Center for Microbial Interface Biology, The Ohio State University, Columbus, Ohio, USA Division of Infectious Diseases, The Ohio State University, Columbus, Ohio, USA Department of Internal Medicine, The Ohio State University, Columbus, Ohio, USA Department of Microbiology, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Larry S
authors.initials: LS
authors.lastname: Schlesinger
authors.affiliation: Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, USA Center for Microbial Interface Biology, The Ohio State University, Columbus, Ohio, USA Division of Infectious Diseases, The Ohio State University, Columbus, Ohio, USA Department of Internal Medicine, The Ohio State University, Columbus, Ohio, USA Department of Microbiology, The Ohio State University, Columbus, Ohio, USA daniel.wozniak@osumc.edu.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Wozniak
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003179:Complement C3b / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding; D011552:Pseudomonas Infections / Q000378:metabolism* / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C547605:OprF protein, Pseudomonas aeruginosa; D003179:Complement C3b