Combined Inhibitory Effects of Citrinin, Ochratoxin-A, and T-2 Toxin on Aquaporin-2.

Aquaporins form a large family of transmembrane protein channel that facilitates selective and fast water transport across the cell membrane. The inhibition of aquaporin channels leads to many water-related diseases such as nephrogenic diabetes insipidus, edema, cardiac arrest, and stroke. Herein, we report the molecular mechanism of mycotoxins (citrinin, ochratoxin-A, and T-2 mycotoxin) inhibition of aquaporin-2 (AQP2) and arginine vasopressin receptor 2. Molecular docking, molecular dynamics simulations, quantum chemical calculations, residue conservation-coupling analysis, sequence alignment, and in vivo studies were utilized to explore the binding interactions between the mycotoxins and aquaporin-2. Theoretical studies revealed that the electrostatic interactions induced by the toxins pulled the key residues (187Arg, 48Phe, 172His, and 181Cys) inward, hence reduced the pore diameter and water permeation. The permeability coefficient of the channel was reduced from native ((3.32 ± 0.75) × 10-14 cm3/s) to toxin-treated AQP2 ((1.08 ± 0.03) × 10-14 cm3/s). The hydrogen bonds interruption and formation of more hydrogen bonds with toxins also led to the reduced number of water permeation. Further, in vivo studies showed renal damages and altered level of aquaporin expression in mycotoxin-treated Mus musculus. Furthermore, the multiple sequence alignments among the model organism along with evolutionary coupling analysis provided the information about the interdependences of the residues in the channel.