Owman C, Mahan L C
Department of Physiology and Neuroscience, Wallenberg Neuroscience Center, University of Lund, Sweden.
Biochem Biophys Res Commun. 1997 Apr 28;233(3):853-6. doi: 10.1006/bbrc.1997.6565.
Xenopus oocytes devoid of their follicular enclosure provide a frequently used expression system for investigating receptors that transduce through activation of adenylyl cyclase following injection of the appropriate mRNA. However, due to a low basal activity of the cyclase they cannot be utilized to investigate receptor-mediated reductions in endogenous cAMP levels. In order to overcome this limitation, a model was designed in which test clones for such inhibitory receptors were co-expressed with a beta 2-adrenoceptor, which elevated cAMP upon exposure to isoproterenol. Following injection of mRNA to express the alpha 2 test receptor in the oocytes, marked reduction in cAMP could be measured after exposure to clonidine. Attenuation of cAMP levels was also seen following co-expression of the dopamine D2 receptor along with dopamine administration. Thus, after inducing a receptor-mediated tone in adenylyl cyclase activity, Xenopus oocytes can be conveniently used to study also ligands that bind to inhibitory G-protein coupled receptors.
去除卵泡包被的非洲爪蟾卵母细胞为研究通过注射适当的信使核糖核酸（mRNA）后激活腺苷酸环化酶进行信号转导的受体提供了一种常用的表达系统。然而，由于环化酶的基础活性较低，它们不能用于研究受体介导的内源性环磷酸腺苷（cAMP）水平的降低。为了克服这一限制，设计了一种模型，其中将此类抑制性受体的测试克隆与β2 -肾上腺素能受体共表达，后者在暴露于异丙肾上腺素时会升高cAMP。在卵母细胞中注射mRNA以表达α2测试受体后，在暴露于可乐定后可测量到cAMP的显著降低。在多巴胺D2受体共表达并给予多巴胺后，也观察到了cAMP水平的降低。因此，在诱导受体介导的腺苷酸环化酶活性变化后，非洲爪蟾卵母细胞可方便地用于研究与抑制性G蛋白偶联受体结合的配体。
