Altered activity of the inhibitory guanyl nucleotide-binding component (Ni) induced by pertussis toxin. Uncoupling of Ni from receptor with continued coupling of Ni to the catalytic unit

• Published in: The Journal of biological chemistry 1984-07, Vol.259 (14), p.8693-8698
• Main Authors: Cote, T E, Frey, E A, Sekura, R D
• Format: Article
• Language: English
• Subjects: Adenosine Diphosphate Ribose - metabolism; Adenylate Cyclase Toxin; Adenylyl Cyclases - metabolism; Animals; Bacterial Toxins - pharmacology; Biological and medical sciences; Cell Membrane - metabolism; Cell physiology; Cholera Toxin - pharmacology; Fundamental and applied biological sciences. Psychology; GTP-Binding Proteins; Guanosine Triphosphate - pharmacology; Guanylyl Imidodiphosphate - pharmacology; Hormonal regulation; Kinetics; Male; Molecular and cellular biology; Pertussis Toxin; Pituitary Gland - metabolism; Rats; Rats, Inbred Strains; Receptors, Cell Surface - metabolism; Receptors, Dopamine - drug effects; Receptors, Dopamine - metabolism; Receptors, Dopamine D2; Spiperone - metabolism; Virulence Factors, Bordetella
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)47207-3

The D-2 dopamine receptor mediates inhibition of adenylate cyclase in rat intermediate lobe; this receptor is linked to cyclase by the inhibitory guanyl nucleotide-binding protein (Ni). The functioning of components in the inhibitory system was compared in control and pertussis toxin-treated tissues. (-)-N-n-Propylnorapomorphine ((-)-NPA), a dopamine agonist, and 5'-guanylyl imidodiphosphate (Gpp(NH)p), a nonhydrolyzable GTP analog, caused a dose-dependent inhibition of adenylate cyclase in control tissue. Pertussis toxin abolished dopamine receptor-mediated inhibition of adenylate cyclase but did not alter Gpp(NH)p-induced inhibition of cyclase. In control tissue, GTP blocked Gpp(NH)p inhibition of cyclase in the absence, but not in the presence of (-)-NPA. Following pertussis toxin treatment, GTP blocked the inhibitory effect of Gpp(NH)p either in the absence or in the presence of (-)-NPA. Pertussis toxin did not alter the number of dopamine receptors or the affinity of the receptor for [3H]spiroperidol, a dopamine antagonist. However, pertussis toxin decreased the potency of (-)-NPA in the binding assay and abolished the ability of GTP to affect agonist binding. Furthermore, pertussis toxin abolished the dopamine receptor-mediated inhibition of immunoreactive alpha-melanocyte-stimulating hormone release, and induced the ADP-ribosylation of the Mr = 41,000 subunit of Ni.