Chung Wilson C J, Pak Toni R, Suzuki Shotaro, Pouliot Wendy A, Andersen Melvin E, Handa Robert J
Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado 80309-0354, USA.
J Comp Neurol. 2007 Nov 20;505(3):249-67. doi: 10.1002/cne.21490.
Estrogens regulate neural processes such as neuronal development, reproductive behavior, and hormone secretion, and signal through estrogen receptor (ER) alpha and ERbeta (here called ERbeta1). Recent studies have found variations in ERalpha and ERbeta1 mRNA splicing in rodents and humans. Functional reporter gene assays suggest that these splicing variations alter ER-mediated transcriptional regulation. Estrogen receptor beta 2 (ERbeta2), an ERbeta1 splice variant containing an 18 amino acid (AA) insert in the ligand binding domain, binds estradiol with approximately 10-fold lower affinity than ERbeta1, suggesting that it may serve as a low-affinity ER. Moreover, ERbeta2 reportedly acts in a dominant-negative fashion when heterodimerized with ERbeta1 or ERalpha. To explore the function of ERbeta2 in brain, an antiserum (TwobetaER.1) targeting the 18 AA insert was developed and characterized. Western blot analysis and transient expression of ERbeta2 in cell lines demonstrated that TwobetaER.1 recognizes ERbeta2. In the adult female rat brain, ERbeta2 immunoreactivity is localized in the cell nucleus and is expressed with a distribution similar to that of ERbeta1 mRNA. ERbeta2 immunoreactive cell numbers were high in, for example, piriform cortex, paraventricular nucleus, supraoptic nucleus, arcuate nucleus, and hippocampal CA regions, whereas it was low in the dentate gyrus. Moreover, ERbeta2 is coexpressed in gonadotropin-releasing hormone and oxytocin neurons. These studies demonstrate ERbeta splice variant proteins in brain and support the hypothesis that ER signaling diversity depends not only on ligand or coregulatory proteins, but also on regional and phenotypic selectivity of ER splice variant proteins.
雌激素调节神经过程，如神经元发育、生殖行为和激素分泌，并通过雌激素受体（ER）α和ERβ（此处称为ERβ1）进行信号传导。最近的研究发现，啮齿动物和人类中ERα和ERβ1的mRNA剪接存在差异。功能性报告基因分析表明，这些剪接变异会改变ER介导的转录调控。雌激素受体β2（ERβ2）是ERβ1的剪接变体，在配体结合域含有18个氨基酸（AA）插入，与雌二醇的结合亲和力比ERβ1低约10倍，这表明它可能作为一种低亲和力的ER发挥作用。此外，据报道，当与ERβ1或ERα异源二聚化时，ERβ2以显性负性方式发挥作用。为了探究ERβ2在大脑中的功能，开发并鉴定了一种针对18个AA插入序列的抗血清（TwobetaER.1）。细胞系中ERβ2的蛋白质印迹分析和瞬时表达表明，TwobetaER.1可识别ERβ2。在成年雌性大鼠大脑中，ERβ2免疫反应性定位于细胞核，其表达分布与ERβ1 mRNA相似。例如，在梨状皮质、室旁核、视上核、弓状核和海马CA区，ERβ2免疫反应性细胞数量较高，而在齿状回中则较低。此外，ERβ2在促性腺激素释放激素和催产素神经元中共同表达。这些研究证明了大脑中存在ERβ剪接变体蛋白，并支持以下假设：ER信号多样性不仅取决于配体或共调节蛋白，还取决于ER剪接变体蛋白的区域和表型选择性。
