An inwardly rectifying whole cell current induced by Gq-coupled receptors.
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.
Buchholz
Björn
B
Renal Division and Center for Clinical Research, University Hospital Freiburg, Breisacherstr. 66, 79106 Freiburg, Germany.
Tauber
Robert
R
Steffl
Daniel
D
Walz
Gerd
G
Köttgen
Michael
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008564:Membrane Potentials / Q000502:physiology*; D043643:Receptor, Muscarinic M1 / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058472:Receptors, Purinergic P2Y1; D011994:Recombinant Proteins / Q000378:metabolism; D014982:Xenopus laevis
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D043643:Receptor, Muscarinic M1; D018160:Receptors, Cytoplasmic and Nuclear; D043562:Receptors, G-Protein-Coupled; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D011994:Recombinant Proteins; D002118:Calcium