Division of Molecular Medicine, Ruđer Bošković Institute, Zagreb, Croatia.
Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia.
J Virol. 2019 Dec 12;94(1). doi: 10.1128/JVI.00663-19.
Cancer-causing human papillomavirus (HPV) E6 oncoproteins have a class I PDZ-binding motif (PBM) on their C termini, which play critical roles that are related to the HPV life cycle and HPV-induced malignancies. E6 oncoproteins use these PBMs to interact with, to target for proteasome-mediated degradation, a plethora of cellular substrates that contain PDZ domains and that are involved in the regulation of various cellular pathways. In this study, we show that both HPV-16 and HPV-18 E6 oncoproteins can interact with Na/H exchange regulatory factor 2 (NHERF-2), a PDZ domain-containing protein, which among other cellular functions also behaves as a tumor suppressor regulating endothelial proliferation. The interaction between the E6 oncoproteins and NHERF-2 is PBM dependent and results in proteasome-mediated degradation of NHERF-2. We further confirmed this effect in cells derived from HPV-16- and HPV-18-positive cervical tumors, where we show that NHERF-2 protein turnover is increased in the presence of E6. Finally, our data indicate that E6-mediated NHERF-2 degradation results in p27 downregulation and cyclin D1 upregulation, leading to accelerated cellular proliferation. To our knowledge, this is the first report to demonstrate that E6 oncoproteins can stimulate cell proliferation by indirectly regulating p27 through targeting a PDZ domain-containing protein. This study links HPV-16 and HPV-18 E6 oncoproteins to the modulation of cellular proliferation. The PDZ domain-containing protein NHERF-2 is a tumor suppressor that has been shown to regulate endothelial proliferation; here, we demonstrate that NHERF-2 is targeted by HPV E6 for proteasome-mediated degradation. Interestingly, this indirectly affects p27, cyclin D1, and CDK4 protein levels and, consequently, affects cell proliferation. Hence, this study provides information that will improve our understanding of the molecular basis for HPV E6 function, and it also highlights the importance of the PDZ domain-containing protein NHERF-2 and its tumor-suppressive role in regulating cell proliferation.
致癌的人类乳头瘤病毒 (HPV) E6 癌蛋白在其 C 末端具有一个 I 类 PDZ 结合基序 (PBM)，这些基序在 HPV 生命周期和 HPV 诱导的恶性肿瘤中发挥着关键作用。E6 癌蛋白利用这些 PBM 与大量含有 PDZ 结构域的细胞底物相互作用，这些底物被靶向用于蛋白酶体介导的降解，这些底物参与各种细胞途径的调节。在这项研究中，我们表明 HPV-16 和 HPV-18 E6 癌蛋白都可以与 PDZ 结构域包含蛋白 Na/H 交换调节因子 2 (NHERF-2) 相互作用，NHERF-2 除了其他细胞功能外，还作为调节内皮细胞增殖的肿瘤抑制因子发挥作用。E6 癌蛋白与 NHERF-2 的相互作用依赖于 PBM，并导致 NHERF-2 的蛋白酶体介导的降解。我们在源自 HPV-16 和 HPV-18 阳性宫颈癌的细胞中进一步证实了这种效应，我们表明在存在 E6 的情况下，NHERF-2 蛋白周转增加。最后，我们的数据表明，E6 介导的 NHERF-2 降解导致 p27 下调和 cyclin D1 上调，从而导致细胞增殖加速。据我们所知，这是第一项表明 E6 癌蛋白通过间接调节 PDZ 结构域包含蛋白来调节 p27 从而刺激细胞增殖的报告。这项研究将 HPV-16 和 HPV-18 E6 癌蛋白与细胞增殖的调节联系起来。含有 PDZ 结构域的蛋白 NHERF-2 是一种已被证明可调节内皮细胞增殖的肿瘤抑制因子；在这里，我们证明 NHERF-2 是 HPV E6 用于蛋白酶体介导的降解的靶标。有趣的是，这间接影响了 p27、cyclin D1 和 CDK4 蛋白水平，从而影响了细胞增殖。因此，这项研究提供了信息，将提高我们对 HPV E6 功能的分子基础的理解，并且还强调了含有 PDZ 结构域的蛋白 NHERF-2 及其在调节细胞增殖中的肿瘤抑制作用的重要性。
