Regulatory Volume Decrease (RVD) is a process by which cells restore their volume when swollen by hypo-osmotic stress. In this study, we have focused on the role played by two different Aquaporins (AQPs), AQP4 and AQP1, in mediating Ca2+ signaling after hypotonic shock and in triggering RVD, together with the Transient Receptor Potential Vanilloid 4 (TRPV4), a Ca2+-permeable channel activated by the membrane stretching. Using biophysical techniques to measure the water plasma membrane permeability of WT and AQP4 KO astrocytes and of cells transfected with AQP4 or AQP1, we showed that both AQPs play a key role in RVD by affecting the initial kinetics of the swollen phase that is faster and higher in amplitude in the presence of AQPs. By calcium imaging we showed that AQP4 and AQP1-mediated cell swelling significantly increases the amplitude of Ca2+ influx inhibited by the TRPV4 inhibitors, Gadolinium (Gad) and Ruthenium Red (RR). Finally, the effect of Ca2+ influx through TRPV4 on the cell volume regulation was analyzed by measuring RVD in the presence of Gad and RR or removing the external Ca2+. Our results show that the RVD kinetic was unchanged in all these conditions, indicating that the TRPV4 mediated Ca2+ influx does not play a role in RVD. All together these results show that 1) AQPs play a key role in mediating Ca2+ signaling after hypotonic shock together with TRPV4, 2) AQPs are the main trigger for RVD, and 3) Ca2+is not fundamental for RVD to occur.
Contribution of Aquaporins and TRPV4 to astrocyte cell volume regulation
Mola M. G.;
2013-01-01
Abstract
Regulatory Volume Decrease (RVD) is a process by which cells restore their volume when swollen by hypo-osmotic stress. In this study, we have focused on the role played by two different Aquaporins (AQPs), AQP4 and AQP1, in mediating Ca2+ signaling after hypotonic shock and in triggering RVD, together with the Transient Receptor Potential Vanilloid 4 (TRPV4), a Ca2+-permeable channel activated by the membrane stretching. Using biophysical techniques to measure the water plasma membrane permeability of WT and AQP4 KO astrocytes and of cells transfected with AQP4 or AQP1, we showed that both AQPs play a key role in RVD by affecting the initial kinetics of the swollen phase that is faster and higher in amplitude in the presence of AQPs. By calcium imaging we showed that AQP4 and AQP1-mediated cell swelling significantly increases the amplitude of Ca2+ influx inhibited by the TRPV4 inhibitors, Gadolinium (Gad) and Ruthenium Red (RR). Finally, the effect of Ca2+ influx through TRPV4 on the cell volume regulation was analyzed by measuring RVD in the presence of Gad and RR or removing the external Ca2+. Our results show that the RVD kinetic was unchanged in all these conditions, indicating that the TRPV4 mediated Ca2+ influx does not play a role in RVD. All together these results show that 1) AQPs play a key role in mediating Ca2+ signaling after hypotonic shock together with TRPV4, 2) AQPs are the main trigger for RVD, and 3) Ca2+is not fundamental for RVD to occur.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
