Interaction of Clostridium botulinum C2 toxin with lipid bilayer membranes and Vero cells: inhibition of channel function by chloroquine and related compounds in vitro and intoxification in vivo.

Abstract

SPECIFIC AIMSC2-II, the binding component of ADP-ribosylating Clostridium botulinum C2 toxin, is involved in C2-mediated intoxication of target cells and forms channels in lipid bilayers. Here we studied the mechanism by which chloroquine and related compounds inhibit the C2-II channel in vitro and C2 toxin-mediated intoxication of Vero cells in vivo. In particular, we investigated the sidedness of this interaction and the relation between 4-aminoquinolone structure and channel function.PRINCIPAL FINDINGS1. Evaluation of the stability constant of the 4-aminoquinolone binding to C2-IIActivated C2-II but not nonactivated C2-II forms ion-permeable channels in lipid bilayer membranes. 4-Aminoquinolones known as potent antimalarial drugs interact with the C2-II channel, thereby blocking the channel. The block was studied using titration experiments. These measurements allow the calculation of the stability constants for 4-aminoquinolone binding to the channel. C2-II was reconstituted into lipid bilayers, then ...