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  • 1
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    GAP domains responsible for ras p21-dependent inhibition of muscarinic atrial K+ channel currents (1992)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1992-01-10
    Description: The interaction between the low molecular weight G protein ras p21 and a guanosine triphosphatase activating protein (GAP) uncouples a heterotrimeric G protein (Gk) from muscarinic receptors. Through the use of isolated atrial cell membranes and genetically engineered GAP deletion mutants, the src homology regions (SH2-SH3) at the amino terminus of GAP have been identified as the domains responsible for this effect. Deletion of the domain required to stimulate the guanosine triphosphatase activity of ras p21 relieves the requirement for ras p21 in this system. A model is presented that suggests that ras p21 induces a conformational change in GAP, which allows the SH2-SH3 regions of GAP to function.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Martin, G A -- Yatani, A -- Clark, R -- Conroy, L -- Polakis, P -- Brown, A M -- McCormick, F -- CA51992-01/CA/NCI NIH HHS/ -- HL36930/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1992 Jan 10;255(5041):192-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, Cetus Corporation, Emeryville, CA 94608.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1553544" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Baculoviridae ; Cell Membrane/metabolism ; Cells, Cultured ; Cloning, Molecular ; GTP-Binding Proteins/*physiology ; GTPase-Activating Proteins ; Genetic Engineering ; Genetic Vectors ; Guanosine 5'-O-(3-Thiotriphosphate)/pharmacology ; Guanosine Triphosphate/pharmacology ; Guinea Pigs ; Heart/*physiology ; Heart Atria ; Models, Biological ; Polymerase Chain Reaction ; Potassium Channels/drug effects/*physiology ; Proteins/genetics/*physiology ; Proto-Oncogene Proteins p21(ras)/*metabolism ; Receptors, Muscarinic/drug effects/*physiology ; ras GTPase-Activating Proteins
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    Rapid beta-adrenergic modulation of cardiac calcium channel currents by a fast G protein pathway (1989)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1989-07-07
    Description: beta-Adrenergic agonists activate the G protein, Gs, which stimulates cardiac calcium currents by both cytoplasmic, indirect and membrane-delimited, direct pathways. To test whether beta-adrenergic agonists might use both pathways in the heart, isoproterenol was rapidly applied to cardiac myocytes, resulting in a biphasic increase in cardiac calcium channel currents that had time constants of 150 milliseconds and 36 seconds. beta-Adrenergic antagonists of a G protein inhibitor blocked both the fast and slow responses, whereas the adenylyl cyclase activator forskolin produced only the slow response. The presence of a fast pathway in the heart can explain what the slow pathway cannot account for: the ability of cardiac sympathetic nerves to change heart rate within a single beat.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yatani, A -- Brown, A M -- HL36930/HL/NHLBI NIH HHS/ -- HL37044/HL/NHLBI NIH HHS/ -- NS23877/NS/NINDS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1989 Jul 7;245(4913):71-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2544999" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Atrial Function ; Calcium Channels/drug effects/*physiology ; Carbachol/pharmacology ; Cells, Cultured ; Colforsin/pharmacology ; GTP-Binding Proteins/*physiology ; Guinea Pigs ; Heart/*physiology ; Isoproterenol/*pharmacology ; Kinetics ; Membrane Potentials/drug effects ; *Signal Transduction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    A monoclonal antibody to the alpha subunit of Gk blocks muscarinic activation of atrial K+ channels (1988)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1988-08-12
    Description: The activated heterotrimeric guanine nucleotide binding (G) protein Gk, at subpicomolar concentrations, mimics muscarinic stimulation of a specific atrial potassium current. Reconstitution studies have implicated the alpha and beta gamma subunits as mediators, but subunit coupling by the endogenous G protein has not been analyzed. To study this process, a monoclonal antibody (4A) that binds to alpha k but not to beta gamma was applied to the solution bathing an inside-out patch of atrial membrane; the antibody blocked carbachol-activated currents irreversibly. The state of the endogenous Gk determined its susceptibility to block by the antibody. When agonist was absent or when activation by muscarinic stimulation was interrupted by withdrawal of guanosine triphosphate (GTP) in the presence or absence of guanosine diphosphate (GDP), the effects of the antibody did not persist. Thus, monoclonal antibody 4A blocked muscarinic activation of potassium channels by binding to the activated G protein in its holomeric form or by binding to the dissociated alpha subunit.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yatani, A -- Hamm, H -- Codina, J -- Mazzoni, M R -- Birnbaumer, L -- Brown, A M -- DK19318/DK/NIDDK NIH HHS/ -- HL36930/HL/NHLBI NIH HHS/ -- HL37044/HL/NHLBI NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1988 Aug 12;241(4867):828-31.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2457252" target="_blank"〉PubMed〈/a〉
    Keywords: Acetylcholine/*pharmacology ; Animals ; *Antibodies, Monoclonal ; Atrial Function ; Carbachol/*pharmacology ; GTP-Binding Proteins/immunology/*physiology ; Guanosine 5'-O-(3-Thiotriphosphate) ; Guanosine Diphosphate/pharmacology ; Guanosine Triphosphate/analogs & derivatives/pharmacology ; Guinea Pigs ; In Vitro Techniques ; Ion Channels/drug effects/*physiology ; Myocardium/*metabolism ; Potassium/*metabolism ; Receptors, Muscarinic/drug effects/*physiology ; Thionucleotides/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    A G protein directly regulates mammalian cardiac calcium channels (1987)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1987-11-27
    Description: A possible direct effect of guanine nucleotide binding (G) proteins on calcium channels was examined in membrane patches excised from guinea pig cardiac myocytes and bovine cardiac sarcolemmal vesicles incorporated into planar lipid bilayers. The guanosine triphosphate analog, GTP gamma S, prolonged the survival of excised calcium channels independently of the presence of adenosine 3',5'-monophosphate (cAMP), adenosine triphosphate, cAMP-activated protein kinase, and the protein kinase C activator tetradecanoyl phorbol acetate. A specific G protein, activated Gs, or its alpha subunit, purified from the plasma membranes of human erythrocytes, prolonged the survival of excised channels and stimulated the activity of incorporated channels. Thus, in addition to regulating calcium channels indirectly through activation of cytoplasmic kinases, G proteins can regulate calcium channels directly. Since they also directly regulate a subset of potassium channels, G proteins are now known to directly gate two classes of membrane ion channels.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yatani, A -- Codina, J -- Imoto, Y -- Reeves, J P -- Birnbaumer, L -- Brown, A M -- HL-31154/HL/NHLBI NIH HHS/ -- HL-36930/HL/NHLBI NIH HHS/ -- HL-37044/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1987 Nov 27;238(4831):1288-92.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2446390" target="_blank"〉PubMed〈/a〉
    Keywords: 3-Pyridinecarboxylic acid, ; 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ; ester/pharmacology ; Animals ; Calcium/metabolism ; Colforsin/pharmacology ; GTP-Binding Proteins/*physiology ; Guanosine 5'-O-(3-Thiotriphosphate) ; Guanosine Triphosphate/analogs & derivatives/pharmacology ; Guinea Pigs ; Heart/*physiology ; Ion Channels/drug effects/*physiology ; Isoproterenol/pharmacology ; Leupeptins/pharmacology ; Membrane Potentials/drug effects ; Phosphorylation ; Thionucleotides/pharmacology ; Ventricular Function
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    Direct activation of mammalian atrial muscarinic potassium channels by GTP regulatory protein Gk (1987)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1987-01-09
    Description: The mammalian heart rate is regulated by the vagus nerve, which acts via muscarinic acetylcholine receptors to cause hyperpolarization of atrial pacemaker cells. The hyperpolarization is produced by the opening of potassium channels and involves an intermediary guanosine triphosphate-binding regulatory (G) protein. Potassium channels in isolated, inside-out patches of membranes from atrial cells now are shown to be activated by a purified pertussis toxin-sensitive G protein of subunit composition alpha beta gamma, with an alpha subunit of 40,000 daltons. Thus, mammalian atrial muscarinic potassium channels are activated directly by a G protein, not indirectly through a cascade of intermediary events. The G protein regulating these channels is identified as a potent Gk; it is active at 0.2 to 1 pM. Thus, proteins other than enzymes can be under control of receptor coupling G proteins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yatani, A -- Codina, J -- Brown, A M -- Birnbaumer, L -- DK-19318/DK/NIDDK NIH HHS/ -- HL-31164/HL/NHLBI NIH HHS/ -- HL-36930/HL/NHLBI NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1987 Jan 9;235(4785):207-11.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2432660" target="_blank"〉PubMed〈/a〉
    Keywords: Acetylcholine/pharmacology ; Animals ; Atrial Function ; Electrophysiology ; Erythrocytes/analysis ; GTP-Binding Proteins/*pharmacology ; Guanosine 5'-O-(3-Thiotriphosphate) ; Guanosine Triphosphate/analogs & derivatives/pharmacology ; Guinea Pigs ; Heart/*physiology ; Humans ; Ion Channels/drug effects/*physiology ; Potassium/*metabolism ; Receptors, Muscarinic/*physiology ; Thionucleotides/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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