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A Novel Biological Role for Peptidyl-Arginine Deiminases: Citrullination of Cathelicidin LL-37 Controls the Immunostimulatory Potential of Cell-Free DNA

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  • Alicia Wong, Universytet Jagielloński
  • ,
  • Danuta Bryzek, Universytet Jagielloński
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  • Ewelina Dobosz, Universytet Jagielloński
  • ,
  • Carsten Scavenius
  • Pavel Svoboda, U.S. Centers for Disease Control and Prevention
  • ,
  • Maria Rapala-Kozik, Universytet Jagielloński
  • ,
  • Adam Lesner, University of Gdansk
  • ,
  • Ivo Frydrych, Palacký University Olomouc
  • ,
  • Jan Enghild
  • Piotr Mydel, Universytet Jagielloński, University of Bergen
  • ,
  • Jan Pohl, U.S. Centers for Disease Control and Prevention
  • ,
  • Paul R Thompson, University of Massachusetts
  • ,
  • Jan Potempa, Universytet Jagielloński, University of Louisville
  • ,
  • Joanna Koziel, Universytet Jagielloński

LL-37, the only human cathelicidin that is released during inflammation, is a potent regulator of immune responses by facilitating delivery of oligonucleotides to intracellular TLR-9, thereby enhancing the response of human plasmacytoid dendritic cells (pDCs) to extracellular DNA. Although important for pathogen recognition, this mechanism may facilitate development of autoimmune diseases. In this article, we show that citrullination of LL-37 by peptidyl-arginine deiminases (PADs) hindered peptide-dependent DNA uptake and sensing by pDCs. In contrast, carbamylation of the peptide (homocitrullination of Lys residues) had no effect. The efficiency of LL-37 binding to oligonucleotides and activation of pDCs was found to be inversely proportional to the number of citrullinated residues in the peptide. Similarly, preincubation of carbamylated LL-37 with PAD2 abrogated the peptide's ability to bind DNA. Conversely, LL-37 with Arg residues substituted by homoarginine, which cannot be deiminated, elicited full activity of native LL-37 regardless of PAD2 treatment. Taken together, the data showed that citrullination abolished LL-37 ability to bind DNA and altered the immunomodulatory function of the peptide. Both activities were dependent on the proper distribution of guanidinium side chains in the native peptide sequence. Moreover, our data suggest that cathelicidin/LL-37 is citrullinated by PADs during NET formation, thus affecting the inflammatory potential of NETs. Together this may represent a novel mechanism for preventing the breakdown of immunotolerance, which is dependent on the response of APCs to self-molecules (including cell-free DNA); overactivation may facilitate development of autoimmunity.

Original languageEnglish
JournalJournal of Immunology
Pages (from-to)2327-2340
Number of pages14
Publication statusPublished - 1 Apr 2018

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  • Journal Article

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