Distinct roles for Gαi2 and Gβγ in signaling to DNA synthesis and Gαi3 in cellular transformation by dopamine D2S receptor activation in BALB/c 3T3 cells
Distinct roles for Gαi2 and Gβγ in signaling to DNA synthesis and Gαi3 in cellular transformation by dopamine D2S receptor activation in BALB/c 3T3 cells
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DOI：
10.1128/mcb.20.5.1497-1506.2000
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发表时间：
2000-03-01
影响因子：
5.3
通讯作者：
Albert, PR
中科院分区：
文献类型：
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作者：
Ghahremani, MH;Forget, C;Albert, PR
细胞增殖的控制依赖于决定细胞对外界信号反应的细胞内介质。在神经内分泌细胞中，多巴胺D2受体短形式（D2S受体）抑制细胞增殖，而在间充质细胞中，同一受体促进细胞增殖。用D2S受体cDNA稳定转染未转化的BALB/c 3T3成纤维细胞，研究指导D2S信号通路刺激细胞增殖的G蛋白。百日咳毒素灭活G(i)和G(o)蛋白并阻断这些细胞中D2S受体的信号传导。通过单独转染百日咳毒素抗性G α (i/o)亚基突变体并测量百日咳毒素处理细胞中d2诱导的反应，重建D2S受体信号通路。该方法确定了G α (i)2和G α (i)3是D2S受体介导的抑制福斯克林刺激的腺苷酸环化酶活性的介质；G α (i)2介导D2S诱导的p42和p44丝裂原活化激酶（MAPK）和DNA合成的刺激，而G α (i)3是转化灶形成所必需的，转染抗毒素G α (i)1 cDNA诱导不依赖于D2S受体激活的异常细胞生长，而G α (o)抑制多巴胺诱导的转化。通过G蛋白受体激酶羧基末端结构域的异位表达来评估G β γ亚基选择性拮抗G β γ活性的作用。这些发现揭示了G蛋白对D2S受体介导的启动DNA合成（G α (i)2和G β - γ）和致癌转化（G α (i)3）的信号传导具有显著和独特的特异性，它们表明MAPK的急性激活与DNA合成增强相关，但与转化无关。
Control of cell proliferation depends on intracellular mediators that determine the cellular response to external cues. In neuroendocrine cells, the dopamine D2 receptor short form (D2S receptor) inhibits cell proliferation, whereas in mesenchymal cells the same receptor enhances cell proliferation. Nontransformed BALB/c 3T3 fibroblast cells were stably transfected with the D2S receptor cDNA to study the G proteins that direct D2S signaling to stimulate cell proliferation. Pertussis toxin inactivates G(i) and G(o) proteins and blocks signaling of the D2S receptor in these cells. D2S receptor signaling was reconstituted by individually transfecting pertussis toxin-resistant G alpha(i/o) subunit mutants and measuring D2-induced responses in pertussis toxin-treated cells. This approach identified G alpha(i)2 and G alpha(i)3 as mediators of the D2S receptor-mediated inhibition of forskolin-stimulated adenylyl cyclase activity; G alpha(i)2-mediated D2S-induced stimulation of p42 and p44 mitogen-activated kinase (MAPK) and DNA synthesis, whereas G alpha(i)3 was required for formation of transformed foci, Transfection of toxin-resistant G alpha(i)1 cDNA induced abnormal cell growth independent of D2S receptor activation, while G alpha(o) inhibited dopamine-induced transformation. The role of G beta gamma subunits was assessed by ectopic expression of the carboxyl-terminal domain of G protein receptor kinase to selectively antagonize G beta gamma activity. Mobilization of G beta gamma subunits was required for D2S-induced calcium mobilization, MAPK activation, and DNA synthesis, These findings reveal a remarkable and distinct G protein specificity for D2S receptor-mediated signaling to initiate DNA synthesis (G alpha(i)2 and G beta gamma) and oncogenic transformation (G alpha(i)3), and they indicate that acute activation of MAPK correlates with enhanced DNA synthesis but not with transformation.