Liggett S B, Bouvier M, O'Dowd B F, Caron M G, Lefkowitz R J, DeBlasi A
Department of Medicine, Duke University Medical Center, Durham, North Carolina.
Biochem Biophys Res Commun. 1989 Nov 30;165(1):257-63. doi: 10.1016/0006-291x(89)91063-2.
We constructed and expressed in a permanent cell line a beta 2-adrenergic receptor with a valine substitution for cysteine 184 of the second putative extracellular loop. The mutant receptor was partially uncoupled from adenylyl cyclase with impaired ability to form the high affinity agonist-receptor-G protein complex, yet displayed more rapid and extensive agonist-induced desensitization. The enhanced desensitization was accompanied by increased agonist promoted, but not cAMP promoted, receptor phosphorylation in intact cells. Thus, not only is impaired desensitization associated with decreased phosphorylation, as we have shown with several mutant beta 2-adrenergic receptors recently, but enhanced desensitization is accompanied by increased agonist promoted receptor phosphorylation. In the case of this cysteine mutant, this may be due to the greater accessibility of the uncoupled receptor for phosphorylation by the beta-adrenergic receptor kinase.
我们构建了一种β2 - 肾上腺素能受体，并在一种永久性细胞系中进行表达，该受体在第二个假定的细胞外环的第184位半胱氨酸处被缬氨酸取代。该突变受体与腺苷酸环化酶部分解偶联，形成高亲和力激动剂 - 受体 - G蛋白复合物的能力受损，但表现出更快速和广泛的激动剂诱导的脱敏作用。增强的脱敏作用伴随着完整细胞中激动剂促进而非cAMP促进的受体磷酸化增加。因此，正如我们最近用几种突变的β2 - 肾上腺素能受体所表明的那样，不仅脱敏受损与磷酸化减少有关，而且增强的脱敏作用伴随着激动剂促进的受体磷酸化增加。就这种半胱氨酸突变体而言，这可能是由于解偶联的受体更容易被β - 肾上腺素能受体激酶磷酸化。
