The estrogen receptor (ER) functions as a dimer and is involved in several different biological functions. However ER dimeric proteins have not been identified by in situ methodologies. Structured illumination microscopy (SIM) has been recently developed, which enabled the localization of protein and protein interaction. Therefore, in this study, we firstly demonstrated that ERs formed both homodimers and heterodimers in breast carcinoma cell lines using Nikon's SIM (N-SIM). ERα/α homodimers were detected in the nuclei of both ERα-positive MCF-7 and T-47D cells; 23.0% and 13.4% of ERα proteins formed ERα/α homodimers, respectively. ERα/β heterodimers were also detected in MCF-7 and T-47D. Approximately 6.6% of both ERα and ERβ1 proteins formed ERα/β1 heterodimers in MCF-7. In addition, 18.1% and 22.4% of ERα and ERβ proteins formed ERα/β2 heterodimers and ERα/β5 heterodimers in MCF-7, respectively. In addition, by using proximity ligation assay (PLA) in MCF-7, estradiol-induced ERα/α homodimers and ERα/β1 heterodimers were both detected after 15 to 45 min of treatment and at 15 min, respectively. The percentage of total ER proteins could also be determined using N-SIM. By using both methods, it has become possible to evaluate precise localization and ratio of ER dimers among different cell types.

中文翻译：

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乳腺癌细胞中雌激素受体二聚体的原位评估：蛋白质-蛋白质相互作用的可视化。

雌激素受体（ER）充当二聚体，并参与多种不同的生物学功能。但是，ER二聚体蛋白尚未通过原位方法鉴定。最近开发了结构照明显微镜（SIM），该技术可实现蛋白质和蛋白质相互作用的定位。因此，在这项研究中，我们首先证明了使用尼康SIM（N-SIM）在乳腺癌细胞系中ER既形成了同二聚体又形成了异二聚体。在ERα阳性MCF-7和T-47D细胞的细胞核中均检测到了ERα/α同型二聚体。ERα蛋白的23.0％和13.4％分别形成ERα/α同型二聚体。在MCF-7和T-47D中也检测到ERα/β异二聚体。在MCF-7中，大约6.6％的ERα和ERβ1蛋白形成ERα/β1异二聚体。此外，还有18.1％和22。在MCF-7中，分别有4％的ERα和ERβ蛋白形成ERα/β2异二聚体和ERα/β5异二聚体。此外，通过在MCF-7中使用邻近连接测定（PLA），分别在治疗15至45分钟和15分钟时检测到雌二醇诱导的ERα/α同二聚体和ERα/β1异二聚体。总ER蛋白的百分比也可以使用N-SIM确定。通过使用这两种方法，可以评估不同细胞类型之间的ER二聚体的精确定位和比率。