Conklin B R, Chabre O, Wong Y H, Federman A D, Bourne H R
Department of Pharmacology, University of California, San Francisco 94143.
J Biol Chem. 1992 Jan 5;267(1):31-4.
Gq mediates hormonal stimulation of phosphoinositide-specific phospholipase C (PI-PLC). We mutated the alpha subunit of Gq (alpha q) to replace arginine 183 with cysteine. Mutations that substitute cysteine for the corresponding arginine residues of alpha s and alpha i2 constitutively activate their respective effector pathways, creating the gsp and gip2 oncogenes. Transient expression of alpha q-R183C in COS-7 and HEK-293 cells constitutively activates PI-PLC, but wild type (WT) alpha q does not. This suggests that the mutated arginines in alpha s, alpha i2, and alpha q share a common function in regulating the active state of these proteins and that the alpha q gene may serve as a target for oncogenic mutations in human tumors. In an attempt to develop an assay for receptor stimulation of recombinant alpha q, we co-expressed receptors with alpha q-WT. We found that the alpha 2-adrenoceptor stimulates PI-PLC activation in HEK-293 cells in a fashion that depends completely on co-expression of alpha q-WT. These findings create an experimental model, similar to that provided for alpha s by S49 cyc- cells, that should make it possible to analyze receptor and effector coupling by mutant alpha q against a null background.
Gq介导激素对磷酸肌醇特异性磷脂酶C（PI-PLC）的刺激作用。我们将Gq的α亚基（αq）的精氨酸183突变为半胱氨酸。用半胱氨酸替代αs和αi2相应精氨酸残基的突变会组成性激活它们各自的效应器途径，从而产生gsp和gip2癌基因。αq-R183C在COS-7和HEK-293细胞中的瞬时表达会组成性激活PI-PLC，但野生型（WT）αq则不会。这表明αs、αi2和αq中突变的精氨酸在调节这些蛋白质的活性状态方面具有共同功能，并且αq基因可能是人类肿瘤致癌突变的一个靶点。为了开发一种检测重组αq受体刺激的方法，我们将受体与αq-WT共表达。我们发现α2肾上腺素能受体以完全依赖于αq-WT共表达的方式刺激HEK-293细胞中的PI-PLC激活。这些发现创建了一个类似于S49 cyc-细胞为αs提供的实验模型，这应该能够在无背景的情况下分析突变型αq的受体和效应器偶联。
