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Peptidyl arginine deiminase from Porphyromonas gingivalis abolishes C5a activity

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  • Ewa Bielecka, Lund University
  • ,
  • Carsten Scavenius
  • Tomasz Kantyka, Jagiellonian University, Poland;
  • ,
  • Monika Jusko, Lund University, Unknown
  • Danuta Mizgalska, Jagiellonian University, Poland;
  • ,
  • Borys Szmigielski, Jagiellonian University, Poland;, Unknown
  • Barbara Potempa, University of Louisville, United States;
  • ,
  • Jan Johannes Enghild
  • Eric Prossnitz, University of New Mexico, Mexico., Unknown
  • Anna M Blom, Lund University
  • ,
  • Jan Potempa, University of Louisville, United States;

Evasion of killing by the complement system, a crucial part of innate immunity, is a key evolutionary strategy of many human pathogens. A major etiological agent of chronic periodontitis, the Gram-negative bacterium Porphyromonas gingivalis produces a vast arsenal of virulence factors that compromise human defense mechanisms. One of these is peptidylarginine deiminase (PPAD), an enzyme unique to P. gingivalis among bacteria, which converts Arg residues in polypeptide chains into citrulline. Here, we report that PPAD citrullination of a critical C-terminal arginine of the anaphylatoxin C5a disabled the protein function. Treatment of C5a with PPAD in vitro resulted in decreased chemotaxis of human neutrophils and diminished calcium signaling in monocytic cell line U937 transfected with the C5a receptor (C5aR) and loaded with a fluorescent intracellular calcium probe: Fura 2-AM. Moreover, a low degree of citrullination of internal arginine residues by PPAD was also detected using mass spectrometry. Further, after treatment of C5 with outer membrane vesicles (OMVs) naturally shed by P. gingivalis we observed generation of C5a totally citrullinated at the C-terminal Arg74 residue (Arg74Cit). In stark contrast only native C5a was detected after treatment with PPAD-null OMVs. Our study suggests reduced antibacterial and proinflammatory capacity of citrullinated C5a, achieved via lower level of chemotactic potential of the modified molecule, and weaker cell activation. In the context of previous studies, which showed crosstalk between C5aR and toll-like receptors, as well as enhanced arthritis development in mice infected with PPAD expressing P. gingivalis, our findings support a crucial role of PPAD in the virulence of P. gingivalis.

Original languageEnglish
JournalJournal of Biological Chemistry
Pages (from-to)32481-32487
Number of pages7
Publication statusPublished - 16 Oct 2014

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