Characterization of endogenous volume-sensitive ion currents in Xenopus laevis oocytes

GALIZIA, LUCIANO; BAZZI, ZAHER; GUASTAFERRI, FLORENCIA V.; OZU, MARCELO; SCHWARZBAUM, PABLO

San Luis

Congreso; XLVIII Reunión Anual SAB; 2019

Sociedad Argentina de Biofísica

The Xenopus laevis oocyte is a well-known heterologous expression system. Severalendogenous ion channels and transporters of Xenopus laevis oocytes have been wellcharacterized, but the identification of volume-sensitive endogenous channels is still amatter of debate. In previous communications we showed that, following shrinkage,oocytes trigger an endogenous ion conductance denoted as Gshrink with simultaneousATP release. Since shrinkage depends on particular features of aquaporins mediatingtransmembrane water transport, and these may modulate ion transport by physicalinteractions, we now evaluated Gshrink using two electrode voltage clamp (TEVC) wheneither aquaporin-1 (AQP1) or -4 (AQP4) were expressed. In addition, we studied thepossible role of the plasma membrane voltage dependent anion channel-1 (pl-VDAC-1)mediating Gshrink. For this purpose, we tested the effect of a hypertonic stimulus Gshrinkusing oocytes injected with an antisense oligonucleotide of pl-VDAC-1, a channelreported to act as a volume-sensitive channel, permeable to Cl- and other anions such asATP. Expression pl-VDAC was reported for Xenopus laevis oocytes, but the associatedcurrents were not functionally characterized. Our results indicate that Gshrink is increasedin both AQP1 and AQP4 injected oocytes, suggesting the effect of AQPs is not specific.Interestingly, injection of pl-VDAC-1 oligonucleotide antisense reduced Gshrink from 3.7 ±0.4 to 1.2 ± 0.2 μS (p < 0.05, n=6) in the absence of any aquaporin expression,suggesting a possible role of this channel as direct or indirect mediator Gshrink.AcknowldegmentsWith grants from UBACYT 20020170100152BA, PIP459 and ANPCyT PICT 2014-0357, PICT-2017-0368.