Investigating the effect of Ser256 phosphorylation on gating of aquaporin-2: Molecular Dynamics study

Regulation of water transport via aquaporins is crucial for osmoregulation and water homeostasis of an organism. This transport of water is regulated either by gating or trafficking wherein AQPs are transported from intracellular storage sites to plasma membrane. It has been proposed that water movement via AQP2 is regulated by post-translational modification. We aimed to explore the structural and functional changes occurring in AQP2 due to Ser256 phosphorylation. We have carried out molecular dynamics simulations to investigate molecular basis of effect of phosphorylation on water permeability of AQP2. MD simulations show that there are mild variations in the pore sizes of different monomers of the phosphorylated and unphosphorylated AQP2. Analysis of inter and intra-monomeric interactions such as hydrogen bond, electrostatic and hydrophobic interactions has been carried out. Structures of the phosphorylated AQP2 do not show any blocking of mouth of pore of the monomers during the course of MD simulations. Further, water permeability calculations do corroborate the above finding. This molecular dynamics study suggests that phosphorylation of C-terminal Ser-256 residue of AQP2 may not be directly responsible for gating mechanism.