Lu Qing, Ebling Heather, Mittler Jens, Baur Wendy E, Karas Richard H
Molecular Cardiology Research Institute, Department of Medicine, and Division of Cardiology, New England Medical Center Hospitals, Tufts University School of Medicine, 750 Washington Street, P.O. Box 80, 02111, Boston, MA, USA.
FEBS Lett. 2002 Apr 10;516(1-3):1-8. doi: 10.1016/s0014-5793(02)02432-8.
In addition to mediating the classical transcriptional effects of estrogen, estrogen receptors (ERs) are now known to regulate gene expression in the absence of estrogen by ligand-independent activation pathways, and to mediate the rapid, non-genomic effects of estrogen as well. ERs have been shown to associate with the cell membrane, and recent studies demonstrate that this subpopulation of membrane-associated ER mediates the rapid effects of estrogen. To date, however, little is known regarding the pathways that regulate the distribution of the ER between the nuclear and membrane fractions. In the current study, we demonstrate membrane localization of transiently transfected ERalpha in human vascular smooth muscle cells, and translocation of ERalpha from the membrane to the nucleus in response to both estrogen-dependent and estrogen-independent stimulation. Mutational analyses identified serine 118 as the critical residue regulating nuclear localization following estrogen-independent stimulation, but not following estrogen stimulation. Induction of nuclear localization of ERalpha by estrogen-independent, but not estrogen-dependent stimulation was blocked by both pharmacologic and genetic inhibition of mitogen-activated protein (MAP) kinase activation. Furthermore, constitutive activation of MAP kinase resulted in nuclear translocation of ERalpha. These overexpression studies support that MAP kinase-mediated phosphorylation of ERalpha induces nuclear localization of the ER in response to estrogen-independent, but not estrogen-dependent stimulation, demonstrating stimulus-specific molecular pathways regulate the nuclear localization of the ER. These findings identify a previously unrecognized pathway that regulates the intracellular localization of the ER, and represent the first demonstration that the distribution of the ER between membrane and nuclear compartments is regulated by physiologic stimuli.
除了介导雌激素的经典转录效应外，现在已知雌激素受体（ERs）可通过非配体依赖性激活途径在无雌激素的情况下调节基因表达，并且还能介导雌激素的快速非基因组效应。已证明ERs与细胞膜相关联，最近的研究表明，这种膜相关ER的亚群介导了雌激素的快速效应。然而，迄今为止，关于调节ER在核和膜部分之间分布的途径知之甚少。在本研究中，我们证明了瞬时转染的ERα在人血管平滑肌细胞中的膜定位，以及ERα在雌激素依赖性和非雌激素依赖性刺激下从膜向核的转位。突变分析确定丝氨酸118是在非雌激素依赖性刺激后而非雌激素刺激后调节核定位的关键残基。非雌激素依赖性而非雌激素依赖性刺激诱导的ERα核定位被丝裂原活化蛋白（MAP）激酶激活的药理学和遗传学抑制所阻断。此外，MAP激酶的组成性激活导致ERα的核转位。这些过表达研究支持MAP激酶介导的ERα磷酸化在非雌激素依赖性而非雌激素依赖性刺激下诱导ER的核定位，表明刺激特异性分子途径调节ER的核定位。这些发现确定了一条以前未被认识的调节ER细胞内定位的途径，并首次证明了ER在膜和核区室之间的分布受生理刺激调节。
