Abstract
Muscarinic acetylcholine receptors modulate the function of a variety of effectors through heterotrimeric G proteins. A prenylated peptide specific to the G protein gamma5 subunit type inhibits G protein activation by the M2 muscarinic receptor in a reconstitution assay. Scrambling the amino acid sequence of the peptide significantly reduces the efficacy of the peptide. The peptide does not disrupt the G protein heterotrimer. In cultured sympathetic neurons, the gamma5 peptide inhibits modulation of Ca(2+) current by the M4 receptor. Peptide activity is specific, the scrambled peptide and peptides specific to two other members of the G protein gamma subunit family are significantly less effective. The gamma5 peptide has no effect on Ca(2+) current modulation by the alpha2-adrenergic and somatostatin receptors. In addition, the gamma5 peptide inhibits muscarinic receptor signaling in spinal cord slices with specificity. These results support a specific role for G protein gamma subunit types in signal transduction, most likely at the receptor-G protein interface.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Brain
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CHO Cells
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Calcium / metabolism
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Calcium Channels / drug effects
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Calcium Channels / physiology*
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Carbachol / pharmacology
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Cattle
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Cells, Cultured
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Clonidine / pharmacology
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Cricetinae
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Cytoplasm / physiology
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Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
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Heterotrimeric GTP-Binding Proteins / chemistry*
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Heterotrimeric GTP-Binding Proteins / metabolism*
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In Vitro Techniques
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N-Methylscopolamine / metabolism
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Neurons / drug effects
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Neurons / physiology*
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Oxotremorine / pharmacology
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Peptide Fragments / chemistry
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Peptide Fragments / pharmacology
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Receptor, Muscarinic M4
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Receptors, Adrenergic, alpha-2 / drug effects
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Receptors, Adrenergic, alpha-2 / physiology
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Receptors, Muscarinic / physiology*
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Receptors, Somatostatin / drug effects
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Receptors, Somatostatin / physiology
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Signal Transduction / physiology*
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Spinal Cord / drug effects
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Spinal Cord / physiology*
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Superior Cervical Ganglion / physiology*
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Transfection
Substances
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Calcium Channels
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Peptide Fragments
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Receptor, Muscarinic M4
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Receptors, Adrenergic, alpha-2
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Receptors, Muscarinic
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Receptors, Somatostatin
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Guanosine 5'-O-(3-Thiotriphosphate)
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Oxotremorine
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Carbachol
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Heterotrimeric GTP-Binding Proteins
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Clonidine
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Calcium
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N-Methylscopolamine