Jiang Xiaohua, Sinnett-Smith James, Rozengurt Enrique
Division of Digestive Diseases, Department of Medicine, CURE: Digestive Diseases Research Center, David Geffen School of Medicine and Molecular Biology Institute, University of California at Los Angeles, CA 90095, USA.
Biochem Biophys Res Commun. 2009 Sep 25;387(3):521-4. doi: 10.1016/j.bbrc.2009.07.060. Epub 2009 Jul 16.
Stimulation of human colonic epithelial T84 cells with the muscarinic receptor agonist carbachol, a stable analog of acetylcholine, induced Akt, p70S6K1 and ERK activation. Treatment of T84 cells with the selective inhibitor of EGF receptor (EGFR) tyrosine kinase AG1478 abrogated Akt phosphorylation on Ser(473) induced by either carbachol or EGF, indicating that carbachol-induced Akt activation is mediated through EGFR transactivation. Surprisingly, AG1478 did not suppress p70S6K1 phosphorylation on Thr(389) in response to carbachol, indicating the G protein-coupled receptor (GPCR) stimulation induces p70S6K1 activation, at least in part, via an Akt-independent pathway. In contrast, treatment with the selective MEK inhibitor U0126 (but not with the inactive analog U0124) inhibited carbachol-induced p70S6K1 activation, indicating that the MEK/ERK/RSK pathway plays a critical role in p70S6K1 activation in GPCR-stimulated T84 cells. These findings imply that GPCR activation induces p70S6K1 via ERK rather than through the canonical PI 3-kinase/Akt/TSC/mTORC1 pathway in T84 colon carcinoma cells.
用毒蕈碱受体激动剂卡巴胆碱（一种乙酰胆碱的稳定类似物）刺激人结肠上皮T84细胞，可诱导Akt、p70S6K1和ERK活化。用表皮生长因子受体（EGFR）酪氨酸激酶选择性抑制剂AG1478处理T84细胞，可消除由卡巴胆碱或表皮生长因子（EGF）诱导的Ser(473)位点的Akt磷酸化，这表明卡巴胆碱诱导的Akt活化是通过EGFR反式激活介导的。令人惊讶的是，AG1478并未抑制卡巴胆碱刺激引起的Thr(389)位点的p70S6K1磷酸化，这表明G蛋白偶联受体（GPCR）刺激至少部分通过一条不依赖Akt的途径诱导p70S6K1活化。相反，用选择性MEK抑制剂U0126（而非无活性类似物U0124）处理可抑制卡巴胆碱诱导的p70S6K1活化，这表明MEK/ERK/RSK途径在GPCR刺激的T84细胞中p70S6K1活化过程中起关键作用。这些发现表明，在T84结肠癌细胞中，GPCR活化通过ERK而非经典的PI 3激酶/Akt/结节性硬化复合物/mTORC1途径诱导p70S6K1活化。
