Specificity of receptor-G protein interactions. Discrimination of Gi subtypes by the D2 dopamine receptor in a reconstituted system.
The selectivity of D2 dopamine receptor-guanine nucleotide-binding protein (G protein) coupling was studied by reconstitution techniques utilizing purified D2 dopamine receptors from bovine anterior pituitary and resolved G proteins from bovine brain, bovine pituitary, and human erythrocyte. Titration of a fixed receptor concentration with varying G protein concentrations revealed two aspects of receptor-G protein coupling. First, Gi2 appeared to couple selectively with the D2 receptor with approximately 10-fold higher affinity than any other tested Gi subtype. Second, the G proteins differed in the maximal receptor-mediated agonist stimulation of the intrinsic GTPase activity. Gi2 appeared to be maximally stimulated by agonist-receptor complex with turnover numbers of approximately 2 min-1. The other Gi subtypes, Gi1 and Gi3, could be only partially activated, resulting in maximal rates of GTPase of approximately 1 min-1. Agonist-stimulated GTPase activity was not detected in preparations containing Go from bovine brain. The differences in maximal agonist-stimulated GTPase rates observed among the Gi subtypes could be explained by differences in agonist-promoted guanyl nucleotide exchange. Both guanosine 5'-3-O-(thio)triphosphate (GTP gamma S) binding and GDP release parameters were enhanced 2-fold for the Gi2 subtype over the other Gi subtypes. These results suggest that even though several types of pertussis toxin substrate may exist in most tissues, a receptor may interact discretely with G proteins, thereby dictating signal transduction mechanisms.
Senogles
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Department of Cell Biology, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710.
Spiegel
A M
AM
Padrell
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Iyengar
R
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Caron
M G
MG
D000818:Animals; D001923:Brain Chemistry; D002417:Cattle; D004912:Erythrocytes / Q000032:analysis; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D010902:Pituitary Gland / Q000032:analysis; D011954:Receptors, Dopamine / Q000302:isolation & purification / Q000378:metabolism*; D017448:Receptors, Dopamine D2; D012243:Rhodopsin / Q000378:metabolism; D015398:Signal Transduction; D013873:Thionucleotides / Q000378:metabolism
D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D012243:Rhodopsin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins