Galectin-8A Inhibits Cry11Aa Binding to ALP1 and APN 2 Receptors and Toxicity Against Aedes aegypti Larvae

Aedes aegypti, a crucial vector mosquito that transmits many diseases that cause millions of deaths worldwide, can be controlled with Bacillus thuringiensis subsp. israelensis (Bti). The larvicidal activity of Bti against Ae. aegypti is due primarily to Cry4Aa, Cry4Ba, and Cry11Aa, and Cyt1Aa, a protein that synergizes the activity of the Cry proteins. Interestingly, Galectins-6 and Galectins-14, members of a family of β-galactoside-binding proteins that play a role in immune responses insects, have been shown to decrease the activity of Bti toxins. The activity of other Galectins, particularly Galectin-8A, against the Cry proteins is not known. Toward this end, we cloned the gene coding for galactin-8A and expressed the recombinant protein and purified protein. The bioassay results indicated that Galectin-8A can also reduce the toxicity of Cry11Aa, but it was much stronger than Galectin-6. To investigate the interactions among Galectin-8A, Cry11Aa, and toxin receptors, Octet Red System analysis, Western blot, far-Western blot, and ELISA assay were also performed. The Octet Red System result showed that Galectin-8A could also bind to BBMVs of Ae. aegypti, with a lower kDa value than that of Galectin-6, indicating that Galectin-8A had a stronger binding affinity to BBMVs than Galectin-6. Western blot, far-Western blot, and ELISA assay analyses also demonstrated that Galectin-8A bound to Ae. aegypti receptor ALP1 and APN2, consistent with the protein docking simulation results. These findings support the conclusion that Galectin-8A blocks with ALP1 and APN2 more effectively than Galectin-6, which may subsequently reduce the toxicity of Cry11Aa in Ae. aegypti.