Coupling of the expressed α(1B)-adrenergic receptor to the phospholipase C pathway in Xenopus oocytes. The role of G(o)

R. D. Blitzer, G. Omri, M. De Vivo, D. J. Carty, R. T. Premont, J. Codina, L. Birnbaumer, S. Cotecchia, M. G. Caron, R. J. Lefkowitz, E. M. Landau, R. Iyengar

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45 Scopus citations

Abstract

α(1B)-Adrenergic receptor mRNA was injected into Xenopus oocytes, resulting in a norepinephrine-evoked Cl- current. The response was proportional to norepinephrine concentration, blocked by prazosin, and dependent on intracellular Ca2+ derived from inositol triphosphate- sensitive stores. Oocytes treated with 2 μg/ml pertussis toxin showed a time-dependent decrease of the norepinephrine response, taking up to 72 h to show an 80% decrease. Overnight treatment with 10 μg/ml pertussis toxin also resulted in 80% reduction. Responses to two other cloned receptors (M(I)- muscarinic and serotonin-1c) expressed in oocytes were also reduced 50% or more by 72 h of pertussis toxin treatment. Pertussis toxin labeling of the cloned Xenopus α(o)-subunit translated in vitro showed that it was a significantly poorer substrate for pertussis toxin than the two mammalian α(o)-subunits expressed and assayed under identical conditions. This unexpected biochemical behavior of the Xenopus α(o)-subunit is in agreement with the rather unusual treatment conditions required to observe the effects of pertussis toxin on the receptor-evoked Cl- current in the oocyte. Injection of mammalian heterotrimeric G(o) but not G(i3) significantly enhanced the norepinephrine-evoked Cl- current in oocytes. Injection of mixtures of anti-sense oligonucleotides to the Xenopus α(o)-subunit reduced the norepinephrine-evoked Cl- current by 60% within 24 h, compared with oocytes injected with the oligonucleotides encoding sense sequences. These studies indicate that the expressed α(1B)-adrenergic receptor, like the native muscarinic receptor, utilizes G(o) to couple to the phospholipase C- mediated Cl- current in Xenopus oocytes.

Original languageEnglish
Pages (from-to)7532-7537
Number of pages6
JournalJournal of Biological Chemistry
Volume268
Issue number10
StatePublished - 1993
Externally publishedYes

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