The Aedes aegypti cadherin receptor expressed in C6/36 mediates cytotoxicity by the Bacillus thuringiensis Cry11A toxin

The cadherin-like receptor plays an important role in the in vivo toxicity of Bacillus thuringiensis Cry proteins. We previously reported that a cadherin-like receptor in Aedes aegypti bound the Cry11A toxin of Bacillus thuringiensis subsp. israelensis with high affinity, Kd ≈ 16.7 nM. We also have data that a cadherin fragment synergizes Cry11A toxicity by 2-3 fold to mosquito larvae. Based on these results, we investigated the function of the cadherin-like receptor in a cell-based system. We established C6/36 mosquito cell lines stably expressing the full-length Aedes cadherin-like receptor. Receptor expression was determined by western blotting using anti-cadherin antibody and by immunofluorescence staining under confocal microscopy. In these cells the cadherin-like receptor was expressed mostly in the cytoplasm, in addition to the plasma membrane. The toxicity of Cry11A to these cells was analyzed by using a MTT cytotoxicity assay using activated Cry11A toxin at final concentration up to 400 nM. Cells expressing the cadherin-like receptor showed sensitivity to the toxin. Cry11A toxin at 400 nM killed approximately 20% of the cells in 3 hours. These results suggest that the cadherin-like receptor functions as a receptor and plays a pivotal role in the in vivo intoxication of Ae. aegypti larvae for Cry11A toxicity.