Instituto de Biología Molecular y Celular de Rosario-CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000, Rosario, Argentina.
BMC Cancer. 2020 Apr 7;20(1):293. doi: 10.1186/s12885-020-06778-5.
Persistent infection with high-risk Human Papillomavirus (HPVs) is associated with the development of cervical cancer. The transforming capacity of these viruses relies on the cooperative action of the E6 and E7 viral oncoproteins. Among the oncogenic activities of E6, the interaction and interference with cell polarity PDZ proteins have been well established. One of the most characterized PDZ targets of HPV E6 is human Disc large 1 (DLG1), a scaffolding protein involved in the control of cell polarity and proliferation. Interestingly, in cervical squamous intraepithelial lesions, alterations in DLG1 expression were observed in association to tumour progression. Moreover, the expression of both HPV E6 and E7 proteins may be responsible for the changes in DLG1 abundance and cell localization observed in the HPV-associated lesions.
Due to the relevance of DLG1 deregulation in tumour development, we have performed an in-depth investigation of the expression of DLG1 in the presence of the HPV oncoproteins in epithelial cultured cells. The effects of HPV E6 and E7 proteins on DLG1 abundance and subcellular localization were assessed by western blot and confocal fluorescence microscopy, respectively.
We demonstrated that the relative abundance of HPV-18 E6 and DLG1 is a key factor that contributes to defining the expression abundance of both proteins. We also show here that a high expression level of DLG1 may negatively affect HPV-18 E6 nuclear expression. Moreover, the co-expression of HPV-18 E6 and E7 produces a striking effect on DLG1 subcellular localization and a co-distribution in the cytoplasmic region. Interestingly, HPV-18 E7 is also able to increase DLG1 levels, likely by rescuing it from the E6-mediated proteasomal degradation.
In general, the data suggest that HPV-18 E6 and E7 may have opposing activities in regards to the regulation of DLG1 levels and may cooperatively contribute to its subcellular redistribution in the HPV context. These findings constitute a step forward in understanding the differential expression of DLG1 during tumour progression in an HPV-associated model.
高危型人乳头瘤病毒（HPV）的持续感染与宫颈癌的发展有关。这些病毒的转化能力依赖于 E6 和 E7 病毒癌蛋白的协同作用。在 E6 的致癌活性中，HPV E6 与人 Disc large 1（DLG1）的相互作用和干扰已得到充分证实，后者是一种参与细胞极性控制和增殖的支架蛋白。有趣的是，在宫颈鳞状上皮内病变中，观察到 DLG1 表达的改变与肿瘤进展有关。此外，HPV E6 和 E7 蛋白的表达可能是 HPV 相关病变中观察到的 DLG1 丰度和细胞定位改变的原因。
由于 DLG1 失调在肿瘤发展中的重要性，我们在培养的上皮细胞中深入研究了 HPV 癌蛋白存在时 DLG1 的表达。通过 Western blot 和共聚焦荧光显微镜分别评估 HPV E6 和 E7 蛋白对 DLG1 丰度和亚细胞定位的影响。
我们证明 HPV-18 E6 和 DLG1 的相对丰度是决定两种蛋白表达丰度的关键因素。我们还表明，DLG1 的高表达水平可能会对 HPV-18 E6 的核表达产生负面影响。此外，HPV-18 E6 和 E7 的共表达对 DLG1 的亚细胞定位产生显著影响，并使其在细胞质区域共分布。有趣的是，HPV-18 E7 还能够增加 DLG1 的水平，可能是通过将其从 E6 介导的蛋白酶体降解中拯救出来。
总的来说，数据表明 HPV-18 E6 和 E7 可能在调节 DLG1 水平方面具有相反的活性，并可能在 HPV 背景下共同促进其亚细胞重新分布。这些发现为理解 HPV 相关模型中肿瘤进展过程中 DLG1 的差异表达迈出了一步。
