Enhanced sensitivity to cholera toxin in female ADP-ribosylarginine hydrolase (ARH1)-deficient mice

Abstract

Cholera toxin, an 84-kDa multimeric protein and a major virulence factor of Vibrio cholerae, uses the ADP-ribosyltransferase activity of its A subunit to intoxicate host cells. ADP-ribosylation is a posttranslational modification of proteins, in which the ADP-ribose moiety of NAD+ is transferred to an acceptor. In mammalian cells, ADP-ribosylation of acceptors appears to be reversible. ADP-ribosyltransferases (ARTs) catalyze the modification of acceptor proteins, and ADP-ribose-acceptor hydrolases (ARHs) cleave the ADP-ribose-acceptor bond. ARH1 specifically cleaves the ADP-ribose-arginine bond. We previously demonstrated a role for endogenous ARH1 in regulating the extent of cholera toxin-mediated fluid and electrolyte abnormalities in a mouse model of intoxication. Murine ARH1-knockout (KO) cells and ARH1-KO mice exhibited increased sensitivity to cholera toxin compared to their wild-type (WT) counterparts. In the current report, we examined the sensitivity to cholera toxin of male and female ARH1-KO and WT mice. Intestinal loops derived from female ARH1-KO mice when injected with cholera toxin showed increased fluid accumulation compared to male ARH1-KO mice. WT mice did not show gender differences in fluid accumulation, ADP-ribosylarginine content, and ADP-ribosyl Gαs levels. Injection of 8-Bromo-cAMP into the intestinal loops also increased fluid accumulation, however, there was no significant difference between female and male mice or in WT and KO mice. Female ARH1-KO mice showed greater amounts of ADP-ribosylated Gαs protein and increased ADP-ribosylarginine content both in whole intestine and in epithelial cells than did male ARH1-KO mice. These results demonstrate that female ARH1-KO mice are more sensitive to cholera toxin than male mice. Loss of ARH1 confers gender sensitivity to the effects of cholera toxin but not of cyclic AMP. These observations may in part explain the finding noted in some clinical reports of enhanced symptoms of cholera and/or diarrhea in women than men.

(ADP-ribosyl)hydrolases: structure, function, and biology

“…In addition, ARH1 plays a role in the protection from Vibrio cholera infections (Kato et al 2007;Watanabe et al 2018). Cholera toxin, which is secreted during infection, inhibits the GTPase activity of the α subunit of the stimulatory guanine nucleotide-binding (G S α) protein by MARylation of an arginine residue, thus maintaining G Sα's active form.…”

“…This results in accumulation of intracellular cAMP, ultimately leading to abnormalities in fluid and electrolyte transport that are the hallmark of Vibrio cholera pathogenesis (Vanden Broeck et al 2007;Catara et al 2019). Arh1 −/− mice exhibit enhanced sensitivity to the toxin with significantly increased fluid accumulation in the intestinal loops (Kato et al 2007;Watanabe et al 2018). Moreover, a crosstalk between arginine-and serine-ADP-ribosylation has been recently reported.…”

ADP-ribosylation signalling and human disease

“…As seen for the bacterial DraG proteins, ARH1 reverses Arg-ADPr synthesized by both mammal endogenous ARTCs and bacterial toxins [64] (figure 1). Indeed, Arh1 -deficient mice show enhanced sensitivity to cholera toxin infection [65]. By contrast, ARH3 shows high activity on O -glycosidic bonds and is the only known enzyme possessing hydrolytic activity against Ser-ADPr [66] (figure 1).…”

A comprehensive review of therapeutic approaches available for the treatment of cholera

“…[105] The potential role for endogenous ARHs in regulating the extent of cholera toxin-mediated fluid and electrolyte abnormalities in a mouse model has been investigated. [106] The role of this route was studied by Kato and collaborators in 2007 [107] using the small intestine (and other cells) from knockout (KO) mice that lacked hydrolase activity. In this study, the CT effects on fluid accumulation in intestinal loops were much greater in KO than in wild-type mice.…”