Departments of Internal Medicine (Cardiovascular Medicine) and Immunobiology and the Raymond and Beverly Sackler Foundation Cardiovascular Laboratory, Yale University School of Medicine, New Haven, CT 06511, USA.
Mol Biol Cell. 2011 Nov;22(22):4415-23. doi: 10.1091/mbc.E11-05-0416. Epub 2011 Sep 21.
In addition to enhancing or repressing transcription, steroid hormone receptors rapidly transduce kinase activation signals. On ligand engagement, an N-terminus-truncated splice isoform of estrogen receptor (ER) α, ER46, triggers membrane-initiated signals, resulting in endothelial nitric oxide synthase (eNOS) activation and endothelial NO production. The orientation of ER46 at the plasma membrane is incompletely defined. With the use of ecliptic pHluorin-fused ER46, total internal reflection fluorescence microscopy in live human endothelial cells illustrates that ER46 can topologically conform to a type I transmembrane protein structure. Mutation of isoleucine-386 at the center of ER46's transmembrane hydrophobic core prevents membrane spanning, obscures the N-terminal ectodomain, and effects a marked reduction in membrane-impermeant estrogen binding with diminished rapid eNOS activation and NO production, despite maintained genomic induction of an estrogen response element-luciferase reporter. Thus there exist pools of transmembrane steroid hormone receptors that are efficient signaling molecules and potential novel therapeutic targets.
除了增强或抑制转录，甾体激素受体还能迅速转导激酶激活信号。配体结合后，雌激素受体（ER）α 的一种 N 端截断剪接异构体 ER46 触发膜起始信号，导致内皮型一氧化氮合酶（eNOS）激活和内皮一氧化氮产生。ER46 在质膜上的取向尚未完全确定。使用 ecliptic pHluorin 融合的 ER46，活的人内皮细胞中的全内反射荧光显微镜表明，ER46 可以拓扑地符合 I 型跨膜蛋白结构。ER46 跨膜疏水区中心的异亮氨酸 386 的突变阻止了跨膜，掩盖了 N 端胞外结构域，并导致膜不可渗透的雌激素结合显著减少，快速 eNOS 激活和 NO 产生减少，尽管维持了雌激素反应元件-荧光素酶报告基因的基因组诱导。因此，存在有效的信号转导分子和潜在的新型治疗靶点的跨膜甾体激素受体池。
