Factors determining the specificity of signal transduction by guanine nucleotide-binding protein-coupled receptors. II. Preferential coupling of the alpha 2C-adrenergic receptor to the guanine nucleotide-binding protein, Go.
Cell to cell communication by many hormones and neurotransmitters involves three major entities: receptor (R), G-protein (G), and effector molecule (E). Plasticity in this system is conferred by the existence of each entity as isoforms or closely related subtypes that are expressed in a tissue-specific and developmentally regulated manner. Factors that determine signal specificity in this system are poorly understood. Such factors include the relative affinity and stoichiometry of R-G or G-E and the possible colocalization of R-G-E in cellular microdomains. Utilizing the alpha 2-adrenergic receptor (alpha 2-AR) system as a representative subfamily of this class of signal transducers, we determined the relative importance of these factors. By analysis of R-G coupling in mammalian cells cotransfected with alpha 2-AR genes and G alpha cDNA, we demonstrate preferential coupling between an alpha 2-AR subtype and Go. Our data implicate R-G affinity as an important determinant of signal transduction specificity and indicate that a critical level of Go alpha is required for coupling. This report indicates the utility of R-G cotransfection in mammalian cells as a "natural environment model" to characterize events occurring at the R-G and G-E interface.
Cellular and Molecular Research Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
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D016475:3T3 Cells; D000316:Adrenergic alpha-Agonists / Q000378:metabolism; D000818:Animals; D000068438:Brimonidine Tartrate; D002462:Cell Membrane / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D015151:Immunoblotting; D007700:Kinetics; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism; D051379:Mice; D010957:Plasmids; D011485:Protein Binding; D011810:Quinoxalines / Q000378:metabolism; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D015016:Yohimbine / Q000378:metabolism
D000316:Adrenergic alpha-Agonists; D008565:Membrane Proteins; D011810:Quinoxalines; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D006165:Guanylyl Imidodiphosphate; D000068438:Brimonidine Tartrate; D019204:GTP-Binding Proteins; D004837:Epinephrine