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

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

Congreso; SAB; 2019

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 a matterof debate. In previous communications we showed that, following shrinkage, oocytes triggeran endogenous ion current denoted as I shrink with simultaneous ATP release. Since shrinkagedepends on particular features of aquaporins mediating transmembrane water transport, andthese may modulate ion transport by physical interactions, we now characterized I shrink wheneither aquaporin-1 (AQP1) or -4 (AQP4) were expressed. In addition, we studied the possiblerole of VDAC-1 mediating I shrink .For this purpose, we tested the effect of a hypertonic stimulus I shrink . using oocytes injected withan antisense oligonucleotide of the plasma membrane voltage dependent anion channel-1 (pl-VDAC-1), a channel reported to act as a volume-sensitive channel, permeable to Cl - and otheranions such as ATP. Expression pl-VDAC was reported for Xenopus laevis oocytes, but theassociated currents were not functionally characterized. Our results indicate that I shrink isincreased in both AQP1 and AQP4 injected oocytes, suggesting the effect of AQPs is notspecific. Interestingly, injection of pl-VDAC-1 oligonucleotide antisense reduced I shrink in theabsence of any aquaporin expression, suggesting a possible role of this channel as direct orindirect mediator I shrink