Arginine-Specific Mono ADP-Ribosylation In Vitro of Antimicrobial Peptides by ADP-Ribosylating Toxins

Abstract

Among the several toxins used by pathogenic bacteria to target eukaryotic host cells, proteins that exert ADP-ribosylation activity represent a large and studied family of dangerous and potentially lethal toxins. These proteins alter cell physiology catalyzing the transfer of the ADP-ribose unit from NAD to cellular proteins involved in key metabolic pathways. In the present study, we tested the capability of four of these toxins, to ADP-ribosylate α- and β- defensins. Cholera toxin (CT) from Vibrio cholerae and heat labile enterotoxin (LT) from Escherichia coli both modified the human α-defensin (HNP-1) and β- defensin-1 (HBD1), as efficiently as the mammalian mono-ADP-ribosyltransferase-1. Pseudomonas aeruginosa exoenzyme S was inactive on both HNP-1 and HBD1. Neisseria meningitidis NarE poorly recognized HNP-1 as a substrate but it was completely inactive on HBD1. On the other hand, HNP-1 strongly influenced NarE inhibiting its transferase activity while enhancing auto-ADP-ribosylation. We conclude that only some arginine-specific ADP-ribosylating toxins recognize defensins as substrates in vitro. Modifications that alter the biological activities of antimicrobial peptides may be relevant for the innate immune response. In particular, ADP-ribosylation of antimicrobial peptides may represent a novel escape mechanism adopted by pathogens to facilitate colonization of host tissues.

Human Defensins Facilitate Local Unfolding of Thermodynamically Unstable Regions of Bacterial Protein Toxins

“…Defensins also inhibit diverse enzymatic toxins, such as the binary anthrax lethal toxin (Kim et al, 2005), Corynebacterium diphtheriae diphtheria toxin (Kim et al, 2006), Pseudomonas aeruginosa exotoxin A (Kim et al, 2006), Clostridium difficile toxin B [TcdB; (Giesemann et al, 2008)], Staphylococcus aureus staphylokinase (Bokarewa and Tarkowski, 2004), and others (Castagnini et al, 2012; Hooven et al, 2012). Notably, bacterial toxins represent a variety of enzymatic and structural classes of proteins and therefore cannot be selected by defensins based solely on their specific activity or structure.…”

Targeting and inactivation of bacterial toxins by human defensins

“…The list of bacterial ARTs inhibited by defensins extends to NarE, ADP-ribosylating toxins from Neisseria meningitidis (mNarE toxin; (Castagnini et al, 2012)) and N. gonorrhoeae (gNarE toxin; (Rodas et al, 2016)), while cholera toxin (CT) and pertussis toxin (PT) were not affected by the peptides, implying that properties unrelated to the specific catalytic activity of the toxins were targeted by the defensins.…”

“…To assess whether bacterial ARTs, might employ similar mechanisms of defensin inactivation, P. aeruginosa exoenzyme S (ExoS), as well as CT, PT, DT, and ETA were examined but found to be unable to ADP-ribosylate HNP1 (Kim et al, 2006; Paone et al, 2002). In partial contradiction, more sensitive detection techniques revealed that CT and another bacterial ART toxin, Escherichia coli heat labile enterotoxin (LT) can ADP-ribosylate HNP1 and hBD1 in vitro (Castagnini et al, 2012). Given that only a small fraction of defensins was modified under ideal experimental conditions in vitro (Castagnini et al, 2012), the in vivo relevance of this modification by bacterial ART toxins is uncertain.…”

“…In partial contradiction, more sensitive detection techniques revealed that CT and another bacterial ART toxin, Escherichia coli heat labile enterotoxin (LT) can ADP-ribosylate HNP1 and hBD1 in vitro (Castagnini et al, 2012). Given that only a small fraction of defensins was modified under ideal experimental conditions in vitro (Castagnini et al, 2012), the in vivo relevance of this modification by bacterial ART toxins is uncertain.…”

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2011–2012

“…Arginine-specific mono ADP-ribosylation in vitro of antimicrobial peptides by ADPribosylating toxins (Castagnini et al, 2012) Interleukin-5 receptor TOF Mutation of N-glycosylation sites to determine effect on function (Ishino et al, 2011) Interleukin-11 TOF (sinapinic), glycoprotein Introduction of O-glycans in the non-core region to investigate function (Yanaka et al, 2011) Lipoproteins…”