Mechanosensitivity and electric field modulates the water flow through plant and animal aquaporins

OZU, MARCELO; ALVEAR ARIAS, JUAN JOSÉ; FERNÁNDEZ, MIGUEL; CAVIGLIA, AGUSTÍN F.; GARATE, JOSÉ ANTONIO; AMODEO, GABRIELA; GONZÁLEZ, CARLOS

Congreso; 20th IUPAB Congress - 45th Annual Meeting of SBBF - 50th Annual Meeting of SBBq; 2021

Aquaporins (AQPs) are part of a large but conservedfamily of transmembrane tetrameric proteins that include water channels as wellas water-solute and/or gas channels. Each subunit has its own permeablepathway. Experiments in oocytes show that the water-transport rate of plant andanimal aquaporins decreases by increasing the osmotic gradient and that thiseffect correlates with membrane tension increments. By other side, moleculardynamic (MD) simulations predict how the water molecules move through thepermeable pathway as well as how they might respond to electric fields. Usingthe heterologous xenopus oocytes system, we studied the mechanosensitivity ofhomo and heterotetramers of the plant FaPIP2;1. In addition, to test theeffects of electric fields on the water transport rate we performed moleculardynamic simulations on homotetramers of FaPIP2;1 and AQP4. Functionalparameters were obtained from the kinetics of cell volume changes withdifferent osmotic gradients. Simulations were performed with NAMD v.2.7 and theCHARMM27 force field, using a homology model of FaPIP2;1 developed with thecrystal of SoPIP2;1 (PDB 2B5F) and the structural data of human AQP4 (PDB3GD8). Our experimental results show that FaPIP2;1 behaves as amechanosensitive aquaporin. In analogy with the study of ion channels, thetransport capacity of AQPs can be evidenced in a plot of water flux versusosmotic gradient (Jw-∆osm). For mechanosensitive AQPs the Jw-∆osm plots show deviations from linearity with high gradients. On the other hand, molecular dynamic simulations reveal that FaPIP2;1 has higher water load capacity than other aquaporins, such as SoPIP2; 1 and AQP4. In addition, MD simulations predict that the water transport rate can change with the applied electric field in both AQP4 and FaPIP2;1. Our results suggest that changes ofmembrane tension or electric field perturbates the water flow through aquaporinchannels.