Electrical field modulates the water flow through aquaporin channels

EMERSON CARMONA; GABRIELA AMODEO; MARCELO OZU; JOSÉ A. GÁRATE; CARLOS GONZÁLEZ; MIGUEL FERNÁNDEZ; RAMÓN LATORRE

Valparaiso

Congreso; Society of General Physiologists (SGP) 73rd Annual Symposium Sociedad de Biofísicos Latinoamericanos (SOBLA) Annual Meeting; 2019

Aquaporins (AQPs) are transmembrane tetrameric proteins that transport water and solutes. Each subunit has its own permeable pathway. Molecular dynamic (MD) simulations predict how the water molecule move through the permeable pathway. However, experimental records are lacking and the effects of the transmembrane electric field are still unknown. Using the heterologous xenopus oocytes system we studied the mechanosensitivity of the plant FaPIP2;1 and the animal AQP4 channels. Functional parameters were obtained from the kinetics of cell volume changes with different osmotic gradients. To test the combined effects of both electric fields and membrane tension on the water transport rate we performed molecular dynamic simulations on homotetramers of FaPIP2;1 and AQP4. Molecular dynamic simulations were performed with NAMD v.2.7 and the CHARMM27 force field, using an homology model of FaPIP2;1 developed with the crystal of SoPIP2;1 (PDB 2B5F) and the structural data of human AQP4 (PDB 3GD8).Our experimental results show that FaPIP2;1 behaves as a mechanosensitive aquaporin. In analogy with the study of ion channels, the transport capacity of AQPs can be evidenced in a plot of water flux versus osmotic gradient (Jw-Δosm). For mechanosensitive AQPs the Jw-Δosm plots show deviations from linearity with high gradients. AQP4 is also mechanosensitive and molecular dynamic simulations predict that the water transport rate can change with the applied electric field. Similar results of MD were obtained with FaPIP2;1. Our results suggest that changes in the electrical field perturbates the movement of water flow through aquaporin channels.Supported by CONICYT-PFCHA/Doctorado Nacional/2017-21170395 (E.C.), CONICYT-PFCHA/Doctorado Nacional/2017-21171141 (M.F.), Fondecyt 1180464 (C.G.), and 1150273 (R.L.). The Centro Interdisciplinario de Neurociencia de Valparaiso is a Millennium Institute supported by the Millennium Scientific Initiative of the Chilean Ministry of Economy, Development, and Tourism (P029-022-F). Grants Ubacyt18-20 and pict17-2338 (G.A.) and UBACyT18-20 and PICT17 0368 (M.O.).