Interactions of muscarinic receptors with the heterotrimeric G proteins Gq and G12: transduction of proliferative signals.
Interactions of muscarinic receptors with the heterotrimeric G proteins Gq and G12: transduction of proliferative signals.
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毒蕈碱受体与异源三聚体 G 蛋白 Gq 和 G12 的相互作用：增殖信号的转导。
DOI：
10.1046/j.1471-4159.1997.68020525.x
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发表时间：
1997
影响因子：
4.7
通讯作者：
Brann,MR
中科院分区：
文献类型：
--
作者：
Burstein,ES;Bräuner-Osborne,H;Spalding,TA;Conklin,BR;Brann,MR
在NIH 3 T3细胞中单独或组合测量m2和m5毒蕈碱乙酰胆碱受体以及一系列野生型、嵌合型和突变型G蛋白的增殖和转化特性，以确定哪些G蛋白介导这些信号，以及改变受体和G蛋白的化学计量可以在多大程度上影响这些信号。使用焦点形成试验和称为R-SAT（受体选择和扩增技术）的新型试验测量反应，其中使用报告基因监测增殖反应。单独地，Gαq和Gα12的GT α-缺陷突变体（GST）、野生型Gαq和m5在R-SAT中具有活性。Gα12 α和m5也能诱导病灶形成。M2在两项试验中均无活性。共表达Gαq β可显著降低m5诱导病灶的能力。在病灶形成试验中未观察到受体/G蛋白组合的协同作用，但通过R-SAT很容易检测到。Gαq与m5的共表达诱导了R-SAT的组成型活性，并使m5激动剂的效力增加了90倍。Gαq也诱发m2的激动剂依赖性反应，但不诱发组成性活性。当这些受体与Gα qi 5（一种含有Gαi2的5个C末端残基的嵌合G蛋白）共表达时，与与Gαq共表达相比，激动剂效力在m2时增加10倍，在m5时降低15倍。Gαq和Gα qi 5分别对m5和m2的增殖反应具有双相作用，在高激动剂浓度下抑制反应。Gα12或Gα 12 i5的共表达对m5的浓度-反应关系没有影响，但都引起了m2的弱反应。我们的结论是，虽然Gα12是一个更有效的癌基因，Gαq转导m5驱动的细胞反应。通过改变可用G蛋白的类型和浓度可以从非促有丝分裂受体引起增殖反应，并且G蛋白可以诱导组成型反应，这表明受体启动信号的大小和类型都可以在体内G蛋白水平上进行调节。
The proliferative and transforming properties of m2 and m5 muscarinic acetylcholine receptors and a series of wild‐type, chimeric, and mutant G proteins were measured alone or in combination in NIH 3T3 cells to determine which G proteins mediate these signals and to what extent these signals can be influenced by changing the stoichiometry of receptors and G proteins. Responses were measured using the focus‐forming assay and a novel assay called R‐SAT (ReceptorSelection andAmplificationTechnology) in which proliferative responses are monitored using a reporter gene. Individually, GTPase‐deficient mutants (⋆) of Gαq and Gα12, wild‐type Gαq, and m5 were active in R‐SAT. Gα12⋆and m5 also induced focus formation. m2 was inactive in both assays. The ability of m5 to induce foci was significantly reduced by coexpression of Gαq⋆. Synergistic effects of receptor/G protein combinations were not observed in focus‐forming assays but were readily detected by R‐SAT. Coexpression of Gαq with m5 induced constitutive activity in R‐SAT and increased the potency of agonists at m5 by 90‐fold. Gαq also evoked agonist‐dependent responses from m2 but not constitutive activity. Agonist potency was increased 10‐fold at m2 and decreased 15‐fold at m5 when these receptors were coexpressed with Gαqi5, a chimeric G protein containing the five C‐terminal residues of Gαi2, compared with coexpression with Gαq. Both Gαq and Gαqi5 had biphasic effects on the proliferative responses to m5 and m2, respectively, inhibiting responses at high agonist concentrations. Coexpression of Gα12 or Gα12i5 had no effect on the concentration‐response relationships of m5, but both elicited weak responses from m2. We conclude that although Gα12 is a more potent oncogene, Gαq transduces m5‐driven cellular responses. The demonstrations that proliferative responses can be elicited from a nonmitogenic receptor by altering the type and concentration of available G proteins and that constitutive responses can be induced by G proteins imply that both the magnitude and type of receptor‐initiated signal can be regulated at the level of G proteins in vivo.