Biochem Biophys Res Commun 2004 Sep 10;3221:177-85. doi: 10.1016/j.bbrc.2004.07.103.

An inwardly rectifying whole cell current induced by Gq-coupled receptors.

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Ca(2+) influx across the plasma membrane after stimulation of G protein-coupled receptors is important for many physiological functions. Here we studied the regulation of an inwardly rectifying whole cell current and its putative role in Ca(2+) entry in Xenopus oocytes. Expression of P2Y(1) or M1 receptors in Xenopus oocytes elicited a characteristic inwardly rectifying current without receptor stimulation. This current displayed distinct activation and inactivation kinetics and was highly Ca(2+)-dependent. After stimulation of endogenous G(q)-coupled receptors in water-injected cells similar currents were observed. We therefore speculated that the current could be activated via Ca(2+) store depletion induced by constitutive stimulation of the IP(3) cascade in cells overexpressing G(q)-coupled receptors. Receptor-independent Ca(2+) store depletion also induced the current. In conclusion, this current is activated after store depletion suggesting a role in Ca(2+) entry after stimulation of G(q)-coupled receptors. Finally, our data do not support the proposed ionotropic properties of the P2Y(1) receptor.

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Species referenced: Xenopus laevis
Genes referenced: gnaq