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

Biochem Biophys Res Commun. 2004 Sep 10;322(1):177-85. doi: 10.1016/j.bbrc.2004.07.103.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium Channels / metabolism*
  • Calcium Signaling / physiology*
  • Cells, Cultured
  • Inositol 1,4,5-Trisphosphate Receptors
  • Membrane Potentials / physiology*
  • Receptor, Muscarinic M1 / metabolism*
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Receptors, G-Protein-Coupled / metabolism
  • Receptors, Purinergic P2 / metabolism*
  • Receptors, Purinergic P2Y1
  • Recombinant Proteins / metabolism
  • Xenopus laevis


  • Calcium Channels
  • Inositol 1,4,5-Trisphosphate Receptors
  • Receptor, Muscarinic M1
  • Receptors, Cytoplasmic and Nuclear
  • Receptors, G-Protein-Coupled
  • Receptors, Purinergic P2
  • Receptors, Purinergic P2Y1
  • Recombinant Proteins
  • Calcium