Expression of Cry1Ac cadherin receptors in insect midgut and cell lines

Localization of Bacillus thuringiensis Cry1A toxin-binding molecules in gypsy moth larval gut sections using fluorescence microscopy

“…These results clearly show that the initial binding sites for the Cry1A toxins are concentrated on the insect cell microvilli but very likely do not reflect irreversible binding associated with the insertion of the toxin into the membranes (Liang et al, 1995). Localization of the Bt Cry toxin binding sites in gypsy moth on the microvilli is consistent with similar observations in other insect species using immunochemical approaches and fluorescence microscopy (Chen et al, 2005;Fernandez et al, 2006;Aimanova et al, 2006).…”

“…A growing body of data suggests that these proteins alone do not promote all of the activity associated with Bt action and implies that the action may be mediated by a multiple-component complex, which remains to be discerned. One hypothesis is that sequential binding of Cry toxins to multiple receptors gives rise to a pre-pore oligomeric toxin complex that precedes membrane insertion and pore formation (Bravo et al, 2004;Aimanova et al, 2006;Pacheco et al, 2009;Arenas et al, 2010). This model, based mainly on studies of the toxin-binding properties of Manduca sexta cadherin and the GPI-anchored APN and alkaline phosphatase in vitro, needs validation and may not be broadly applicable to other insects.…”

Role of Receptors in Bacillus thuringiensis Crystal Toxin Activity

“…In contrast, an analysis of the cytoplasmic domain did not reveal sequences known to interact with intracellular proteins such as catenins (33). While classical cadherins are located primarily within adherens junctions involved in cell-cell adhesion (4), lepidopteran cadherin-like proteins have been identified on the apical membrane of midgut columnar epithelial cells (3,24,66,124), the target site of Cry toxins (16,19,20,24). The expression of cadherin has been shown to vary with developmental stage and increases progressively from the first to the fifth instar in M. sexta larvae (124).…”

“…Human embryonic kidney (HEK) cells expressing H. virescens cadherin were also treated with Cry1Ab or Cry1Ac, and although membrane blebbing was observed in some cells, cytotoxicity could not be demonstrated (3). Based on these results, it was proposed that other receptors, such as ALP or aminopeptidase, may be necessary for full toxicity (3,87).…”

Current models of the mode of action of Bacillus thuringiensis insecticidal crystal proteins: A critical review

“…Similarly, RNA silencing of either the cadherin (Fabrick et al, 2009;Soberón et al, 2007b) or the aminopeptidase (Rajagopal et al, 2002;Sivakumar et al, 2007) genes alone can cause resistance to Cry toxins. The model is more difficult to reconcile, however, with the observation that heterologous expression of either the cadherin receptors (Aimanova et al, 2006;Dorsch et al, 2002;Flannagan et al, 2005;Hua et al, 2004aHua et al, , 2004bJurat-Fuentes and Adang, 2006b;Nagamatsu et al, 1999Nagamatsu et al, , 1998Tsuda et al, 2003;Zhang et al, 2005) or the aminopeptidase receptors (Gill and Ellar, 2002;Sivakumar et al, 2007) alone can render the host cells sensitive to one or several of the Cry1A toxins. In these cases, according to the model, the untreated host cells would have to possess the other type of receptor while being tolerant to the toxins.…”