Binding of Cry1Ab toxin, a Bacillus thuringiensis insecticidal toxin, to proteins of the bovine intestinal epithelial cell: An in vitro study

Abstract

Cry toxins produced by Bacillus thuringiensis are insecticidal toxins and have been recently introduced to genetically modified (GM) organisms. The toxins are considered harmless to humans and farm animals; however, it remains unclear whether the toxins affect the mammalian intestinal epithelium, the primary portal and absorption site after ingestion. Therefore, we performed immunohistochemical and ligand blot analyses using brush border membrane vesicles to investigate the interaction of Cry1Ab toxin, a popular Cry toxin developed in GM corn, with bovine intestinal epithelium, with special attention to the presence of Cry1Ab toxin-binding proteins of the epithelial cell. We found that Cry1Ab toxin binds to actin, a cytoskeletal protein. However, the toxin did not bind to aminopeptidase N, cadherin, or alkaline phosphatase, all of which are cell membrane receptors or candidate proteins necessary for the development of toxicity in susceptible insect cells. The present results and previous observations that Cry toxins have little acute toxicity on mammalian cells indicate that Cry1Ab toxin is able to bind to cytoskeletal actin, but that the bovine intestinal epithelial cell lacks membrane receptors, which are necessary for the toxin to exert its toxicity on the cell.

Single amino acid mutation in an ATP-binding cassette transporter gene causes resistance to Bt toxin Cry1Ab in the silkworm, Bombyx mori

“…Proteins in the PAGE gel were transferred onto PVDF membranes (Hybond-P; GE Healthcare) by Transblot SD (Bio-Rad). After blocking with skim milk, the membrane was incubated with rabbit antiserum against Cry1A toxin (40), then with peroxidase-labeled anti-rabbit antibody (GE Healthcare), and visualized using a HistMark TrueBlue Peroxidase System (KPL).…”

Specificity determinants for Cry insecticidal proteins: Insights from their mode of action

“…For instance, Cry toxins do bind to mammalian proteins in vitro (Shimada et al, 2006b;Vazquez-Padron et al, 2000), but this interaction is mostly non-specific (Hofmann et al, 1988) and thus is not conducive to formation of toxin pores (Shimada et al, 2006a). More difficult to explain are reports of high affinity toxin binding, which suggests toxin insertion in the membrane (Liang et al, 1995), associated with low susceptibility, as in the case of Cry1Ac and Spodoptera frugiperda (Garczynski et al, 1991) or Lymantria dispar (Wolfersberger, 1990).…”

Histopathological Investigation of the Stomach of Rats Fed a 60% Genetically Modified Corn Diet

“…An in vitro study on bovine intestinal cells [73] found that the Cry1Ab protein binds to the apical surface of enterocytes. Specifically, the protein was bound to actin, a major protein of the cytoskeleton.…”