G protein subunits and the stimulation of phospholipase C by Gs-and Gi-coupled receptors: Lack of receptor selectivity of Galpha(16) and evidence for a synergic interaction between Gbeta gamma and the alpha subunit of a receptor activated G protein.
G protein subunits and the stimulation of phospholipase C by Gs-and Gi-coupled receptors: Lack of receptor selectivity of Galpha(16) and evidence for a synergic interaction between Gbeta gamma and the alpha subunit of a receptor activated G protein.
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DOI：
10.1073/pnas.93.7.2827
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发表时间：
1996-04
影响因子：
11.1
通讯作者：
Xi Zhu;Lutz Birnbaumer
中科院分区：
文献类型：
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作者：
Xi Zhu;Lutz Birnbaumer
促黄体生成素、加压素和异丙肾上腺素儿茶酚胺激活的刺激性鸟嘌呤核苷酸结合蛋白（Gs）偶联受体单独和与G β γ二聚体、其相应的Galphas、G1-偶联的M2毒蕈碱受体（M2 R）（促黄体生成激素受体、2型加压素受体和1型和2型β肾上腺素能受体）和G1-偶联的M2毒蕈碱受体（M2 R）在COS细胞中瞬时表达。（Galalpha（s）或Galalpha（i3））和Galalpha（q）或Galalpha（i6）。磷脂酶C（PLC）的活性，从预纳入肌[3 H]肌醇磷酸生产评估，然后确定深入了解受体和G蛋白之间的差异耦合偏好。观察到以下情况：（i）所有测试的受体都能够响应于激动剂占据而刺激PLC活性。M2 R对百日咳毒素敏感。(ii)正如预期的那样，Ga（q）的表达促进了激动剂诱导的PLC活化，其在受体之间变化很大（对于2型加压素受体为400%，而对于M2 R仅为30%），Ga（16）的表达促进了任何测试受体对PLC的活化，因此对一种受体与另一种受体几乎没有区别。(iii)G β γ使基础（激动剂非依赖性）PLC活性升高2- 4倍，证实了G β γ刺激PLC β的已证实能力。(iv)在共表达过量G β γ的细胞中，通过其各自的配体激活所表达的受体引起激动剂刺激PLC活性，在M2 R的情况下，其不被百日咳毒素（PTX）阻断，这表明由PTX不敏感的PLC刺激G α亚基介导，推测为但不一定是Gq家族的。(v)由M2 R引起的G β γ和PTX不敏感的G α的作用是协同的，表明一种或多种形式的PLC在G蛋白亚基的条件或双重调节下的可能性，使得一种刺激对另一种刺激敏感。
Stimulatory guanine nucleotide binding protein (Gs)-coupled receptors activated by luteinizing hormone, vasopressin, and the catecholamine isoproterenol (luteinizing hormone receptor, type 2 vasopressin receptor, and types 1 and 2 beta-adrenergic receptors) and the Gi-coupled M2 muscarinic receptor (M2R) were expressed transiently in COS cells, alone and in combination with Gbeta gamma dimers, their corresponding Galphas (Galpha(s), or Galpha(i3)) and either Galpha(q) or Galpha(16). Phospholipase C (PLC) activity, assessed by inositol phosphate production from preincorporated myo[3H]inositol, was then determined to gain insight into differential coupling preferences among receptors and G proteins. The following were observed: (i) All receptors tested were able to stimulate PLC activity in response to agonist occupation. The effect of the M2R was pertussis toxin sensitive. (ii) While, as expected, expression of Galpha(q) facilitated an agonist-induced activation of PLC that varied widely from receptor to receptor (400% with type 2 vasopressin receptor and only 30% with M2R), expression of Galpha(16) facilitated about equally well the activation of PLC by any of the tested receptors and thus showed little if any discrimination for one receptor over another. (iii) Gbeta gamma elevated basal (agonist independent) PLC activity between 2- and 4-fold, confirming the proven ability of Gbeta gamma to stimulate PLCbeta. (iv) Activation of expressed receptors by their respective ligands in cells coexpressing excess Gbeta gamma elicited agonist stimulated PLC activities, which, in the case of the M2R, was not blocked by pertussis toxin (PTX), suggesting mediation by a PTX-insensitive PLC-stimulating Galpha subunit, presumably, but not necessarily, of the Gq family. (v) The effects of Gbeta gamma and the PTX-insensitive Galpha elicited by M2R were synergistic, suggesting the possibility that one or more forms of PLC are under conditional or dual regulation of G protein subunits such that stimulation by one sensitizes to the stimulation by the other.