Role of the second and third intracellular loops of metabotropic glutamate receptors in mediating dual signal transduction activation
Role of the second and third intracellular loops of metabotropic glutamate receptors in mediating dual signal transduction activation
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DOI：
10.1074/jbc.273.10.5615
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发表时间：
1998-03-06
影响因子：
4.8
通讯作者：
Duvoisin, RM
中科院分区：
文献类型：
--
作者：
Francesconi, A;Duvoisin, RM
基于序列同源性和结构相似性，代谢性谷氨酸受体（mGluRs）、细胞外Ca2+感应受体、γ -氨基丁酸B型受体和信息素受体在较大的G蛋白偶联受体超家族中属于一个不同的家族。当在异种系统中表达时，I组mGluRs可以激活双信号转导途径，磷酸肌苷的转换和cAMP的产生。为了研究这些偶联性质的结构基础，我们在mGluR1 α的第二和第三胞内环（i2和i3）中引入了单氨基酸取代。野生型和突变型受体在人胚胎肾293细胞中表达，并分析了它们刺激这两种信号级联反应的能力。每个结构域似乎对磷脂酶C和腺苷酸环化酶的偶联至关重要。在i2中，发现Thr（695）、Lys（697）和Ser（702）选择性参与与G类α亚基(s)的相互作用，而Pro（698）的突变和Cys(694)-Thr（695）的缺失仅影响G(s)的偶联。此外，突变K690A深刻地改变了mGluR1 α信号传导特性，并赋予该受体与抑制性cAMP途径偶联的能力。在i3中，我们发现了两个残基，Arg（775）和Phe(781)，它们对两种途径的偶联至关重要，因为它们的取代导致受体失活。
On the basis of sequence homology and structural similarities, metabotropic glutamate receptors (mGluRs), extracellular Ca2+-sensing receptor, gamma-aminobutyric acid type B receptor, and pheromone receptors are enlisted in a distinct family within the larger G protein-coupled receptor superfamily, When expressed in heterologous systems, group I mGluRs can activate dual signal transduction pathways, phosphoinositides turnover and cAMP production. To investigate the structural basis of these coupling properties, we introduced single amino acid substitutions within the second and third intracellular loops (i2 and i3) of mGluR1 alpha. Wildtype and mutant receptors were expressed in human embryonic kidney 293 cells and analyzed for their capacity to stimulate both signaling cascades. Each domain appeared to be critical for the coupling to phospholipase C and adenylyl cyclase. Within i2, Thr(695), Lys(697), and Ser(702) were found to be selectively involved in the interaction with G class alpha subunit(s), whereas mutation of Pro(698) and the deletion Cys(694)-Thr(695) affected only G(s) coupling. Furthermore, the mutation K690A profoundly altered mGluR1 alpha signaling properties and imparted to the receptor the ability to couple to the inhibitory cAMP pathway. Within i3, we uncovered two residues, Arg(775) and Phe(781), that are crucial for coupling to both pathways, since their substitution leads to receptor inactivation.