%0 Journal Article %1 Bunemann2000 %A Bunemann, M. %A Meyer, T. %A Pott, L. %A Hosey, M. %D 2000 %J J Biol Chem %K & *Pertussis *Potassium Animals Bordetella/*metabolism CHO Cell Channels Channels, Channels/metabolism Cholinergic/metabolism Cricetinae Factors, G GTP-Binding Humans Inwardly Inwardly-Rectifying Muscarinic/*metabolism P1/metabolism Patch-Clamp Potassium Potassium/*metabolism Protein-Coupled Proteins/metabolism Purinergic Rectifying Surface/*antagonists Techniques Toxin Transfection Virulence inhibitors Receptor %N 17 %P 12537-45 %T Novel inhibition of gbetagamma-activated potassium currents induced by M(2) muscarinic receptors via a pertussis toxin-insensitive pathway %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=10777542 %V 275 %X G(i) protein-coupled receptors such as the M(2) muscarinic acetylcholine receptor (mAChR) and A(1) adenosine receptor have been shown to activate G protein-activated inwardly rectifying K(+) channels (GIRKs) via pertussis toxin-sensitive G proteins in atrial myocytes and in many neuronal cells. Here we show that muscarinic M(2) receptors not only activate but also reversibly inhibit these K(+) currents when stimulated with agonist for up to 2 min. The M(2) mAChR-mediated inhibition of the channel was also observed when the channels were first activated by inclusion of guanosine 5'-O-(thiotriphosphate) in the pipette. Under these conditions the M(2) mAChR-induced inhibition was quasi-irreversible, suggesting a role for G proteins in the inhibitory process. In contrast, when GIRK currents were maximally activated by co-expressing exogenous Gbetagamma, the extent of acetylcholine (ACh)-induced inhibition was significantly reduced, suggesting competition between the receptor-mediated inhibition and the large pool of available Gbetagamma subunits. The signaling pathway that led to the ACh-induced inhibition of GIRK channels was unaffected by pertussis toxin pretreatment. Furthermore, the internalization and agonist-induced phosphorylation of M(2) mAChR was not required because a phosphorylation- and internalization-deficient mutant of the M(2) mAChR was as potent as the wild-type counterpart. Pharmacological agents modulating various protein kinases or phosphatidylinositol 3-kinase did not affect the inhibition of GIRK currents. Furthermore, the signaling pathway that mediates GIRK current inhibition was found to be membrane-delimited because bath application of ACh did not inhibit GIRK channel activity in cell-attached patches. Other G protein-coupled receptors including M(4) mAChR and alpha(1A) adrenergic receptors also caused the inhibition, whereas other G protein-coupled receptors including A(1) and A(3) adenosine receptors and alpha(2A) and alpha(2C) adrenergic receptors could not induce the inhibition. The presented results suggest the existence of a novel signaling pathway that can be activated selectively by M(2) and M(4) mAChR but not by adenosine receptors and that involves non-pertussis toxin-sensitive G proteins leading to an inhibition of Gbetagamma-activated GIRK currents in a membrane-delimited fashion.

@article{Bunemann2000, abstract = {G(i) protein-coupled receptors such as the M(2) muscarinic acetylcholine receptor (mAChR) and A(1) adenosine receptor have been shown to activate G protein-activated inwardly rectifying K(+) channels (GIRKs) via pertussis toxin-sensitive G proteins in atrial myocytes and in many neuronal cells. Here we show that muscarinic M(2) receptors not only activate but also reversibly inhibit these K(+) currents when stimulated with agonist for up to 2 min. The M(2) mAChR-mediated inhibition of the channel was also observed when the channels were first activated by inclusion of guanosine 5'-O-(thiotriphosphate) in the pipette. Under these conditions the M(2) mAChR-induced inhibition was quasi-irreversible, suggesting a role for G proteins in the inhibitory process. In contrast, when GIRK currents were maximally activated by co-expressing exogenous Gbetagamma, the extent of acetylcholine (ACh)-induced inhibition was significantly reduced, suggesting competition between the receptor-mediated inhibition and the large pool of available Gbetagamma subunits. The signaling pathway that led to the ACh-induced inhibition of GIRK channels was unaffected by pertussis toxin pretreatment. Furthermore, the internalization and agonist-induced phosphorylation of M(2) mAChR was not required because a phosphorylation- and internalization-deficient mutant of the M(2) mAChR was as potent as the wild-type counterpart. Pharmacological agents modulating various protein kinases or phosphatidylinositol 3-kinase did not affect the inhibition of GIRK currents. Furthermore, the signaling pathway that mediates GIRK current inhibition was found to be membrane-delimited because bath application of ACh did not inhibit GIRK channel activity in cell-attached patches. Other G protein-coupled receptors including M(4) mAChR and alpha(1A) adrenergic receptors also caused the inhibition, whereas other G protein-coupled receptors including A(1) and A(3) adenosine receptors and alpha(2A) and alpha(2C) adrenergic receptors could not induce the inhibition. The presented results suggest the existence of a novel signaling pathway that can be activated selectively by M(2) and M(4) mAChR but not by adenosine receptors and that involves non-pertussis toxin-sensitive G proteins leading to an inhibition of Gbetagamma-activated GIRK currents in a membrane-delimited fashion.}, added-at = {2010-12-14T18:12:02.000+0100}, author = {Bunemann, M. and Meyer, T. and Pott, L. and Hosey, M.}, biburl = {https://www.bibsonomy.org/bibtex/2c38524d6d668560499468a9f85202585/pharmawuerz}, endnotereftype = {Journal Article}, interhash = {980477a8f0fab2ab4fae658ec3589242}, intrahash = {c38524d6d668560499468a9f85202585}, issn = {0021-9258 (Print) 0021-9258 (Linking)}, journal = {J Biol Chem}, keywords = {& *Pertussis *Potassium Animals Bordetella/*metabolism CHO Cell Channels Channels, Channels/metabolism Cholinergic/metabolism Cricetinae Factors, G GTP-Binding Humans Inwardly Inwardly-Rectifying Muscarinic/*metabolism P1/metabolism Patch-Clamp Potassium Potassium/*metabolism Protein-Coupled Proteins/metabolism Purinergic Rectifying Surface/*antagonists Techniques Toxin Transfection Virulence inhibitors Receptor}, month = {Apr 28}, note = {Bunemann, M Meyer, T Pott, L Hosey, M HL 50121/HL/NHLBI NIH HHS/United States Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. United states The Journal of biological chemistry J Biol Chem. 2000 Apr 28;275(17):12537-45.}, number = 17, pages = {12537-45}, shorttitle = {Novel inhibition of gbetagamma-activated potassium currents induced by M(2) muscarinic receptors via a pertussis toxin-insensitive pathway}, timestamp = {2010-12-14T18:20:38.000+0100}, title = {Novel inhibition of gbetagamma-activated potassium currents induced by M(2) muscarinic receptors via a pertussis toxin-insensitive pathway}, url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=10777542}, volume = 275, year = 2000 }