title: Host S-nitrosylation inhibits clostridial small molecule-activated glucosylating toxins.
abstract: The global prevalence of severe Clostridium difficile infection highlights the profound clinical significance of clostridial glucosylating toxins. Virulence is dependent on the autoactivation of a toxin cysteine protease, which is promoted by the allosteric cofactor inositol hexakisphosphate (InsP(6)). Host mechanisms that protect against such exotoxins are poorly understood. It is increasingly appreciated that the pleiotropic functions attributed to nitric oxide (NO), including host immunity, are in large part mediated by S-nitrosylation of proteins. Here we show that C. difficile toxins are S-nitrosylated by the infected host and that S-nitrosylation attenuates virulence by inhibiting toxin self-cleavage and cell entry. Notably, InsP(6)- and inositol pyrophosphate (InsP(7))-induced conformational changes in the toxin enabled host S-nitrosothiols to transnitrosylate the toxin catalytic cysteine, which forms part of a structurally conserved nitrosylation motif. Moreover, treatment with exogenous InsP(6) enhanced the therapeutic actions of oral S-nitrosothiols in mouse models of C. difficile infection. Allostery in bacterial proteins has thus been successfully exploited in the evolutionary development of nitrosothiol-based innate immunity and may provide an avenue to new therapeutic approaches.
authors.affiliation: Department of Gastroenterology & Hepatology, University of Texas Medical Branch, Galveston, Texas, USA. tcsavidg@utmb.edu
authors.forename: Tor C
authors.initials: TC
authors.lastname: Savidge
authors.forename: Petri
authors.initials: P
authors.lastname: Urvil
authors.forename: Numan
authors.initials: N
authors.lastname: Oezguen
authors.forename: Kausar
authors.initials: K
authors.lastname: Ali
authors.forename: Aproteem
authors.initials: A
authors.lastname: Choudhury
authors.forename: Vinay
authors.initials: V
authors.lastname: Acharya
authors.forename: Irina
authors.initials: I
authors.lastname: Pinchuk
authors.forename: Alfredo G
authors.initials: AG
authors.lastname: Torres
authors.forename: Robert D
authors.initials: RD
authors.lastname: English
authors.forename: John E
authors.initials: JE
authors.lastname: Wiktorowicz
authors.forename: Michael
authors.initials: M
authors.lastname: Loeffelholz
authors.forename: Raj
authors.initials: R
authors.lastname: Kumar
authors.forename: Lianfa
authors.initials: L
authors.lastname: Shi
authors.forename: Weijia
authors.initials: W
authors.lastname: Nie
authors.forename: Werner
authors.initials: W
authors.lastname: Braun
authors.forename: Bo
authors.initials: B
authors.lastname: Herman
authors.forename: Alfred
authors.initials: A
authors.lastname: Hausladen
authors.forename: Hanping
authors.initials: H
authors.lastname: Feng
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Stamler
authors.forename: Charalabos
authors.initials: C
authors.lastname: Pothoulakis
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry / Q000378:metabolism*; D018938:Caco-2 Cells; D016360:Clostridioides difficile / Q000472:pathogenicity*; D003015:Clostridium Infections / Q000188:drug therapy*; D057056:Cysteine Proteases / Q000378:metabolism; D004768:Enterotoxins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007082:Ileum / Q000382:microbiology / Q000473:pathology; D051379:Mice; D008958:Models, Molecular; D009569:Nitric Oxide / Q000378:metabolism; D010833:Phytic Acid / Q000378:metabolism; D011487:Protein Conformation; D026403:S-Nitrosothiols / Q000627:therapeutic use; D018709:Statistics, Nonparametric; D014774:Virulence
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D026403:S-Nitrosothiols; C041348:tcdA protein, Clostridium difficile; D009569:Nitric Oxide; D010833:Phytic Acid; D057056:Cysteine Proteases