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This Article Full Text Full Text (PDF) All Versions of this Article: 586/8/2049    most recent jphysiol.2007.148346v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Bender, K. Articles by Kienitz, M.-C. PubMed PubMed Citation Articles by Bender, K. Articles by Kienitz, M.-C. Related Collections Cellular

¹ Institute of Physiology, Ruhr-University Bochum, D-44780 Bochum, Germany

The effect of β-adrenergic stimulation on endogenous G-protein-activated K⁺ (GIRK) current has been investigated in atrial myocytes from hearts of adult rats. β-Adrenergic stimulation (10 µM isoprenaline, Iso) had no effect on activation kinetics, peak current or steady-state current but resulted in slowing of deactivation upon washout of acetylcholine (ACh), the time constant (_d) being increased by a factor of about 2.5. The effect of Iso could be mimicked by inclusion of cAMP (500 µM) in the filling solution of the patch clamp pipette. The Iso-induced increase in _d was blocked by the selective β₁ receptor antagonist CGP-20112A (2 µM) and by the PKA inhibitor H9 (100 µM included in the pipette solution). A candidate for mediating these effects is RGS10, one of the regulators of G-protein signalling (RGS) species expressed in cardiac myocytes. Overexpression of RGS10 by adenoviral gene transfer resulted in a reduction in _d of 60%. Sensitivity of _d to Iso remained in cells overexpressing RGS10. Overexpression of RGS4 caused a comparable reduction in _d, which became insensitive to Iso. Expression of an RGS10 carrying a mutation (RGS10-S168A), which deletes a PKA phosphorylation site, caused a decrease in _d comparable to overexpression of wild-type RGS10. Sensitivity of _d to Iso was lost in RGS10-S168A-expressing myocytes. Silencing of RGS10 by means of adenovirus-mediated transcription of a short hairpin RNA did not affect basal _d but removed sensitivity to Iso. These data suggest that endogenous RGS10 has GTPase-activating protein (GAP) activity on the G-protein species that mediates activation of atrial GIRK channels. Moreover, RGS10, via PKA-dependent phosphorylation, enables a crosstalk between β-adrenergic and muscarinic cholinergic signalling.

(Received 20 November 2007; accepted after revision 14 February 2008; first published online 14 February 2008)
Corresponding author L. Pott: Institute of Physiology, Ruhr-University Bochum, D-44780 Bochum, Germany. Email: lutz.pott{at}rub.de