Koch W J, Hawes B E, Inglese J, Luttrell L M, Lefkowitz R J
Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710.
J Biol Chem. 1994 Feb 25;269(8):6193-7.
The beta gamma subunits (G beta gamma) of heterotrimeric G proteins modulate the activity of several signal-transducing effector molecules including G protein-coupled receptor kinases. G beta gamma binds to the carboxyl terminus of the beta-adrenergic receptor kinase (beta ARK) and regulates its activity. To investigate the effect of such a G beta gamma-binding domain on heterologous G beta gamma interactions, various receptors that can stimulate phospholipase C and/or type II adenylate cyclase were coexpressed in COS-7 cells with the carboxyl terminus of beta ARK1. Phosphoinositol hydrolysis in response to activation of receptors that stimulate phospholipase C via Gi beta gamma (alpha 2-adrenergic and M2-muscarinic cholinergic receptors) was markedly inhibited by the coexpressed beta ARK1 polypeptide, whereas that mediated by Gq alpha subunits (alpha 1-adrenergic and M1-muscarinic cholinergic receptors) was unaffected. Increased cellular cAMP levels due to stimulation of receptors and coexpressed adenylate cyclase II displayed marked inhibition in the presence of the beta ARK1 polypeptide. Moreover, inhibition of adenylate cyclase produced by alpha 2-adrenergic receptor stimulation (a Gi alpha-mediated process) was unaffected, indicating that the beta ARK1 polypeptide provides a useful tool for distinguishing between G alpha and G beta gamma pathways.
异源三聚体G蛋白的βγ亚基（Gβγ）可调节多种信号转导效应分子的活性，包括G蛋白偶联受体激酶。Gβγ与β肾上腺素能受体激酶（βARK）的羧基末端结合并调节其活性。为了研究这种Gβγ结合结构域对异源Gβγ相互作用的影响，将能刺激磷脂酶C和/或II型腺苷酸环化酶的各种受体与βARK1的羧基末端在COS-7细胞中共表达。通过Giβγ（α2肾上腺素能和M2毒蕈碱胆碱能受体）刺激磷脂酶C的受体激活后引起的磷酸肌醇水解，被共表达的βARK1多肽显著抑制，而由Gqα亚基（α1肾上腺素能和M1毒蕈碱胆碱能受体）介导的磷酸肌醇水解则不受影响。在存在βARK1多肽的情况下，由于受体刺激和共表达的腺苷酸环化酶II导致的细胞内cAMP水平升高表现出明显的抑制作用。此外，α2肾上腺素能受体刺激产生的腺苷酸环化酶抑制作用（一种由Giα介导的过程）不受影响，这表明βARK1多肽为区分Gα和Gβγ途径提供了一种有用的工具。
