División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México (UNAM), México, D. F., Mexico.
Cell Signal. 2013 Apr;25(4):829-38. doi: 10.1016/j.cellsig.2012.12.023. Epub 2013 Jan 3.
Epithelial-mesenchymal transition (EMT), proliferation and migration of RPE cells characterize the development of proliferative vitreoretinopathy (PVR) and other fibro-proliferative eye diseases leading to blindness. A common event in these pathologies is the alteration of the BRB which allows the interaction of RPE cells with thrombin, a pro-inflammatory protease contained in serum. Thrombin promotion of cytoskeletal reorganization, proliferation, and migration has been reported in different cell types, although the molecular mechanisms involved in these processes remain poorly understood. Our previous work demonstrated that thrombin promotes RPE cell proliferation, cytoskeletal remodeling and migration, hallmark processes in the development of PVR. Thrombin induction of RPE cell proliferation requires PI3K, PDK1, and Akt/PKB (Akt) signaling leading to cyclin D1 gene expression. Since Akt functions as an upstream activator of mechanistic target of rapamycin complex 1 (mTORC1) and is also a downstream target for mTORC2, the aim of this work was to determine whether mTOR is involved in thrombin-induced RPE cell proliferation by regulating cyclin D1 expression in immortalized rat RPE-J cell line. Results demonstrate that thrombin-induced cyclin D1 expression and cell proliferation require Akt-independent phosphorylation/activation of mTOR at Ser 2448 mediated by PI3K/PKC-ζ/ERK1/2 signaling, concomitant to Akt-dependent activation of p70S6K carried by mTORC1.
上皮-间充质转化 (EMT)、RPE 细胞的增殖和迁移是增生性玻璃体视网膜病变 (PVR) 和其他纤维增生性眼病发展的特征，导致失明。这些病变的一个共同事件是 BRB 的改变，允许 RPE 细胞与凝血酶相互作用，凝血酶是一种包含在血清中的促炎蛋白酶。已报道凝血酶促进不同细胞类型的细胞骨架重排、增殖和迁移，尽管这些过程中涉及的分子机制仍知之甚少。我们之前的工作表明，凝血酶促进 RPE 细胞增殖、细胞骨架重塑和迁移，这是 PVR 发展的标志性过程。凝血酶诱导的 RPE 细胞增殖需要 PI3K、PDK1 和 Akt/PKB (Akt) 信号通路，导致细胞周期蛋白 D1 基因的表达。由于 Akt 作为雷帕霉素复合物 1 (mTORC1) 的上游激活剂，也是 mTORC2 的下游靶点，本研究的目的是确定 mTOR 是否通过调节 immortalized rat RPE-J 细胞系中 cyclin D1 的表达参与凝血酶诱导的 RPE 细胞增殖。结果表明，凝血酶诱导的 cyclin D1 表达和细胞增殖需要 Akt 非依赖性的 mTOR 在丝氨酸 2448 处的磷酸化/激活，由 PI3K/PKC-ζ/ERK1/2 信号介导，与 mTORC1 携带的 Akt 依赖性的 p70S6K 激活同时发生。
