Pertussis Toxin Uncouples Enkephalin-Mediated Inhibition of Rabbit Luteal Adenylyl Cyclase
Hormonally responsive adenylyl cyclases are membrane-bound enzyme systems which consist of at least five distinct components: receptors for stimulatory and inhibitory hormones; transducing proteins called Gs and Gi, respectively, which mediate the effects of hormone-occupied receptor and function in a guanine nucleotide- and Mg ion-dependent fashion; and a catalytic component, which produces cAMP (for review on the component nature of adenylyl cyclases, see 1). Previous studies from our laboratory indicate that rabbit corpora lutea contain an adenylyl cyclase system that, in addition to being stimulated by gonadotropin and catecholamines (2,3), is attenuated by guanine nucleotides and enkephalin (4,5) suggesting the presence of Gi. As first demonstrated by Katada and Ui (6,7), one method to substantiate the existence of Gi in a given tissue is to treat the tissue with pertussis toxin and a [P]NAD, demonstrate the [P] ADP-ribosylation of a membrane protein with an Mr of 40–41,000 daltons and show that this treatment uncouples inhibitory receptors linked to adenylyl cyclase. In this study we present such data establishing the existence of Gi in the rabbit corpus luteum.
KeywordsAdenylate Cyclase Adenylyl Cyclase Cholera Toxin Adenine Nucleotide Guanine Nucleotide
Unable to display preview. Download preview PDF.
- 1.Birnbaumer L, Codina J, Mattera R. Regulation of hormone receptors and adenylyl cyclases by guanine nucleotide binding N proteins. Recent Prog Horm Res 1985; 41:41–99.Google Scholar
- 2.Birnbaumer L, Yang PC, Hunzicker-Dunn M, Bockaert J, Duran JM. Adenylyl cyclase activities in ovarian tissues. I. Homogenization and conditions of assay in Graffian follicles and corpora lutea of rabbits, rats, and pigs: regulation by ATP and some comparative properties. Endocrinology 1976; 99:163–84.PubMedCrossRefGoogle Scholar
- 14.Mattera R, Codina J, Sekura RD, Birnbaumer L. The interaction of nucleotides with pertussis toxin. Direct evidence for a nucleotide binding site on the toxin regulating the rate of ADP-ribosylation of Ni, the inhibitory regulatory component of adenylyl cyclase. J Biol Chem 1986; 261:11173–9.PubMedGoogle Scholar