Kumar Manish, Kong Kathleen, Javier Ronald T
Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.
Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
J Virol. 2014 Dec;88(24):14268-77. doi: 10.1128/JVI.02324-14. Epub 2014 Sep 24.
The E4-ORF1 gene of human adenoviruses encodes a 14-kDa protein that promotes viral replication as well as cellular metabolic reprogramming, survival, and transformation by constitutively activating cellular phosphatidylinositol 3-kinase (PI3K). We recently reported that the E4-ORF1 protein from subgroup D human adenovirus type 9 upregulates and oncogenically activates PI3K by a novel mechanism involving separate interactions of E4-ORF1 with cellular discs large 1 (Dlg1) and PI3K to form a ternary complex that translocates to the plasma membrane (K. Kong, M. Kumar, M. Taruishi, and R. T. Javier, PLoS Pathog. 10:e1004102, 2014, doi:10.1371/journal.ppat.1004102). The current study was carried out to investigate whether other human adenovirus E4-ORF1 proteins share this mechanism of action. The results showed that in human MCF10A epithelial cells, stable expression of E4-ORF1 proteins encoded by representative human adenovirus serotypes from subgroups A to D induce ternary complex formation, Dlg1-dependent PI3K activation, PI3K protein elevation, Dlg1 and PI3K membrane recruitment, and PI3K-dependent cellular transformation. The first three of these E4-ORF1 activities were also observed in MCF10A cells infected with each wild-type human adenovirus from subgroups A to D. Our findings indicate that most, if not all, human adenovirus E4-ORF1 proteins share a conserved molecular mechanism of PI3K activation, which confers a common capacity to promote oncogenic transformation in human epithelial cells.
PI3K activation by the adenovirus E4-ORF1 protein mediates oncogenic cellular transformation by human adenovirus type 9, augments viral protein expression and replication by human adenovirus type 5, and dysregulates cellular glucose and lipid metabolism by human adenovirus type 36. For the first time, we report that E4-ORF1 proteins from human adenoviruses in subgroups A to D evolved a conserved molecular mechanism to mediate constitutive PI3K activation that can provoke oncogenic transformation in human epithelial cells. The results raise potential safety concerns about the use of vectors encoding the E4-ORF1 gene in human gene therapy and vaccination. Our findings further suggest that the conserved mechanism revealed here may be targeted for development of therapeutic drugs to treat and prevent adenovirus-associated human diseases.
人类腺病毒的E4 - ORF1基因编码一种14 kDa的蛋白质，该蛋白质通过持续激活细胞磷脂酰肌醇3 -激酶（PI3K）来促进病毒复制以及细胞代谢重编程、存活和转化。我们最近报道，来自9型D亚组人类腺病毒的E4 - ORF1蛋白通过一种新机制上调并致癌激活PI3K，该机制涉及E4 - ORF1与细胞盘大蛋白1（Dlg1）和PI3K分别相互作用形成三元复合物，该复合物转位至质膜（K. Kong、M. Kumar、M. Taruishi和R. T. Javier，《公共科学图书馆·病原体》10：e1004102，2014，doi：10.1371/journal.ppat.1004102）。本研究旨在调查其他人类腺病毒E4 - ORF1蛋白是否共享这种作用机制。结果表明，在人MCF10A上皮细胞中，来自A至D亚组的代表性人类腺病毒血清型编码的E4 - ORF1蛋白的稳定表达诱导三元复合物形成、Dlg1依赖性PI3K激活、PI3K蛋白升高、Dlg1和PI3K膜募集以及PI3K依赖性细胞转化。在感染了来自A至D亚组的每种野生型人类腺病毒的MCF10A细胞中也观察到了E4 - ORF1的前三种活性。我们的研究结果表明，大多数（如果不是全部）人类腺病毒E4 - ORF1蛋白共享一种保守的PI3K激活分子机制，这赋予了在人上皮细胞中促进致癌转化的共同能力。
腺病毒E4 - ORF1蛋白激活PI3K介导9型人类腺病毒的致癌细胞转化，增强5型人类腺病毒的病毒蛋白表达和复制，并失调36型人类腺病毒的细胞葡萄糖和脂质代谢。我们首次报道，A至D亚组的人类腺病毒的E4 - ORF1蛋白进化出一种保守的分子机制来介导组成型PI3K激活，这可引发人上皮细胞的致癌转化。这些结果引发了对在人类基因治疗和疫苗接种中使用编码E4 - ORF1基因的载体的潜在安全担忧。我们的研究结果进一步表明，此处揭示的保守机制可能成为开发治疗和预防腺病毒相关人类疾病的治疗药物的靶点。
