Song Robert X, Barnes Christopher J, Zhang Zhenguo, Bao Yongde, Kumar Rakesh, Santen Richard J
Department of Internal Medicine and Biomolecular Research Facility, University of Virginia School of Medicine, Charlottesville, VA 22903, USA.
Proc Natl Acad Sci U S A. 2004 Feb 17;101(7):2076-81. doi: 10.1073/pnas.0308334100. Epub 2004 Feb 5.
Our previous studies demonstrated that 17beta-estradiol (E2) rapidly induces the interaction of estrogen receptor alpha (ERalpha) with the adapter protein Shc, the translocation of ERalpha to the cell membrane, and the formation of dynamic membrane structures in MCF-7 breast cancer cells. The present study examined how E2 causes ERalpha to translocate to the region of the plasma membrane and focused on mechanisms whereby Shc and the insulin-like growth factor-1 receptor (IGF-1R) mediate this process. Shc physically interacts with IGF-1R in the plasma membrane, and E2 activates IGF-1R. We reasoned that ERalpha, when bound to Shc, would be directed to the region of the plasma membrane by the same processes, causing membrane translocation of Shc. We confirmed that E2 rapidly induced IGF-1R phosphorylation and demonstrated that E2 induced formation of a ternary protein complex among Shc, ERalpha, and IGF-1R. Knock down of Shc with a specific small inhibitory RNA decreased the association of ERalpha with IGF-1R by 87%, suggesting that Shc is a crucial molecule in the formation of this ternary complex. Confocal microscopy studies provided further confirmation of the functional roles of Shc and the IGF-1R in the translocation of ERalpha to the region of the membrane. Down-regulation of Shc, ERalpha, or IGF-1R with specific small inhibitory RNAs all blocked E2-induced mitogen-activated protein kinase phosphorylation. Together, our results demonstrate that Shc and IGF-1R serve as key elements in the translocation of ERalpha to the cell membrane and in the facilitation of ERalpha-mediated rapid E2 action.
我们之前的研究表明，17β-雌二醇（E2）能迅速诱导雌激素受体α（ERα）与衔接蛋白Shc相互作用，促使ERα转位至细胞膜，并在MCF-7乳腺癌细胞中形成动态膜结构。本研究探讨了E2如何使ERα转位至质膜区域，并聚焦于Shc和胰岛素样生长因子-1受体（IGF-1R）介导这一过程的机制。Shc在质膜上与IGF-1R发生物理相互作用，且E2能激活IGF-1R。我们推测，当ERα与Shc结合时，会通过相同过程被导向质膜区域，从而导致Shc的膜转位。我们证实E2能迅速诱导IGF-1R磷酸化，并证明E2能诱导Shc、ERα和IGF-1R之间形成三元蛋白复合物。用特异性小干扰RNA敲低Shc可使ERα与IGF-1R的结合减少87%，这表明Shc是形成该三元复合物的关键分子。共聚焦显微镜研究进一步证实了Shc和IGF-1R在ERα转位至膜区域过程中的功能作用。用特异性小干扰RNA下调Shc、ERα或IGF-1R均能阻断E2诱导的丝裂原活化蛋白激酶磷酸化。总之，我们的结果表明，Shc和IGF-1R是ERα转位至细胞膜以及促进ERα介导的E2快速作用的关键因素。
