Response of mouse intestinal loop to botulinum C2 toxin: enterotoxic activity induced by cooperation of nonlinked protein components

Abstract

Botulinum C2 toxin, which is composed of two nonlinked protein components, components I and II, induced fluid accumulation in mouse intestinal loops. The secretory response to C2 toxin was initiated after a lag period of 1 to 2 h and increased gradually for at least 10 h. The activity of C2 toxin was enhanced by treatment with trypsin and abolished by neutralization with anti-component I or anti-component II sera. Neither component I nor component II alone induced the fluid accumulation in intestinal loops. The intestinal loop activity was demonstrated with the culture supernatants of strains of Clostridium botulinum types C and D that produced C2 toxin, but not with culture supernatants of strains that did not. None of the botulinum type A through F neurotoxins induced fluid accumulation in mouse intestinal loops. The results indicate that, in addition to lethal and vascular permeability activities, C2 toxin has an enterotoxic activity for which the cooperation of components I and II is necessary. The fluid accumulation in intestinal loops inoculated with C2 toxin was not diminished by removal of the toxin from the loops. Moreover, the secretory response was positive when intestinal lumina were exposed to component II followed by the removal of the component and inoculation with component I, but it was negative when the intestinal lumina were exposed to component I followed by the removal of the component and inoculation with component II. These results suggest that the secretory response of mouse intestinal loops to C2 toxin is induced by the binding of component II to the epithelial cell surfaces of the intestines and the consequent binding or penetration of component I into the cells.

Molecular basis for the pathological actions of Clostridium perfringens iota toxin

“…Unlike diphtheria toxin and P. aeruginosa exotoxin, it does not typically cause cell death. The botulinum binary toxin superficially mimics cholera toxin and related substances, because it does promote the movement of fluids across membranes (11,19,20,25), but an action of this toxin on nucleotide-binding proteins has not been reported.…”

“…Iota toxin appears to share certain properties with the botulinum binary toxin, including the ability to promote the movement of fluids across membranes (5,11,19,20,24). There are also the obvious similarities that both toxins are * Corresponding author.…”

Lethal and Dermonecrotic Activities of Clostridium perfringens Iota Toxin: Biological Activities Induced by Cooperation of Two Nonlinked Components

“…On the other hand, C. botulinum and C. spiroforme have been reported to produce binary toxins (consisting of light and heavy chain components), each of which is similar in molecular weight and action (11,12,14,15). It has been reported that these light chain components ADP-ribosylate synthetic substrates such as homo-poly-L-arginine and actin-like proteins in platelets (12,13), and that the heavy chain component of C. botulinum C2 toxin is responsible for binding of the light chain component to the eucaryotic cells surface (4,(6)(7)(8). On the other hand, little is known about the relationship, between Ia and I, components in lethality and dermonecrosis caused by iota toxin.…”

Visualizations of binding and internalization of two nonlinked protein components of botulinum C2 toxin in tissue culture cells

“…These results indicate that even when the two components of C2T are incubated separately, component I binds to the cell surface bound with T-II and is processed together with T-II during internalization, as was observed with cells exposed simultaneously to both components. Previous studies by indirect immunofluorescence staining have shown that both UT-II and T-II, the binding component of C2T, bind to isolated epithelial cells and to brush borders of mouse intestine, while component I, the active component of the toxin, binds to cells and brush borders only in the presence of T-II (6). In these experiments, these findings were confirmed with two directly fluorescence-labeled components of C2T in tissue culture cells, and the difference in the dynamic processes of components I and II after binding to the cells was visualized.…”

“…These two molecules are functionally different proteins: component II is a binding subunit, and component I is an ADP-ribosyltransferase whose substrate is cytoplasmic actin (7,11). The toxin has various biological activities, lethality, enterotoxicity, and cytotoxicity, all of which are activated by trypsinization of a mixture of the two components and elicited by their cooperation (5,6). These activities of C2T are caused by ADPribosylation of cytoplasmic actin by component I (11).…”