TGF-beta1 is an apoptogenic agent for mammary epithelial cells (MEC). The molecular mechanism of the TGF-beta1-induced apoptosis remains, however, obscure. In the present study we used laser scanning cytometry, confocal microscopy and immunogold electron microscopy to analyze the expression, aggregation and co-localization of caspase-8, Bid, Bax and VDAC-1. These proteins are regarded as the most important factors involved in the regulatory phase of TGF-beta1-induced apoptosis. Apoptosis in HC11 mouse MEC manifested with a simultaneous increase in expression and subcellular aggregation of caspase-8, Bid, Bax and VDAC-1. Confocal microscopy revealed a strong pattern of co-localization of examined proteins during both early and late apoptosis. Experiments with double- and triple-staining immunoelectron microscopy showed a co-localization of Bax/Bid, caspase-8/Bax/Bid, and Bax/VDAC-1, on the membranes of mitochondria, Golgi apparatus, rough endoplasmic reticulum, nuclear envelope, nuclear pore, and within the nucleus. In conclusion, the observed pattern of changes in aggregation and subcellular localization of caspase-8, Bid, Bax and VDAC-1 during TGF-beta1-induced apoptosis in HC11 mouse MEC suggests an interaction between these proteins and formation of multimeric complexes on organellar membranes, thus controlling their permeability for intracellular mediators of apoptosis.

中文翻译：

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在暴露于TGF-beta1的小鼠乳腺上皮HC11细胞中凋亡调节蛋白的共定位。

TGF-beta1是乳腺上皮细胞（MEC）的凋亡发生剂。TGF-β1诱导的细胞凋亡的分子机制仍然不清楚。在本研究中，我们使用激光扫描细胞术，共聚焦显微镜和免疫金电子显微镜来分析caspase-8，Bid，Bax和VDAC-1的表达，聚集和共定位。这些蛋白质被认为是参与TGF-β1诱导的细胞凋亡调控阶段的最重要因素。HC11小鼠MEC中的凋亡表现为caspase-8，Bid，Bax和VDAC-1的表达和亚细胞聚集的同时增加。共聚焦显微镜显示在早期和晚期凋亡期间被检查蛋白的共定位模式很强。双色和三色免疫电子显微镜实验表明，Bax / Bid共定位，caspase-8 / Bax / Bid和Bax / VDAC-1，位于线粒体，高尔基体，粗糙的内质网，核膜，核孔和核内。总之，在TGF-β1诱导的HC11小鼠MEC凋亡过程中，caspase-8，Bid，Bax和VDAC-1的聚集和亚细胞定位变化的观察模式表明，这些蛋白之间的相互作用与细胞器膜上多聚体复合物的形成有关，从而控制它们对细胞凋亡的细胞内介质的渗透性。