Valianou Matthildi, Cox Andrew M, Pichette Benjamin, Hartley Shannon, Paladhi Unmesha Roy, Astrinidis Aristotelis
a Department of Biochemistry and Molecular Biology ; Drexel University College of Medicine ; Philadelphia , PA USA.
Cell Cycle. 2015;14(3):399-407. doi: 10.4161/15384101.2014.986394.
The mechanistic target of rapamycin complex 1 (mTORC1) increases translation, cell size and angiogenesis, and inhibits autophagy. mTORC1 is negatively regulated by hamartin and tuberin, the protein products of the tumor suppressors TSC1 and TSC2 that are mutated in Tuberous Sclerosis Complex (TSC) and sporadic Lymphangioleiomyomatosis (LAM). Hamartin interacts with the centrosomal and mitotic kinase polo-like kinase 1 (PLK1). Hamartin and tuberin deficient cells have abnormalities in centrosome duplication, mitotic progression, and cytokinesis, suggesting that the hamartin/tuberin heterodimer and mTORC1 signaling are involved in centrosome biology and mitosis. Here we report that PLK1 protein levels are increased in hamartin and tuberin deficient cells and LAM patient-derived specimens, and that this increase is rapamycin-sensitive. Pharmacological inhibition of PLK1 by the small-molecule inhibitor BI-2536 significantly decreased the viability and clonogenic survival of hamartin and tuberin deficient cells, which was associated with increased apoptosis. BI-2536 increased p62, LC3B-I and GFP-LC3 punctae, and inhibited HBSS-induced degradation of p62, suggesting that PLK1 inhibition attenuates autophagy. Finally, PLK1 inhibition repressed the expression and protein levels of key autophagy genes and proteins and the protein levels of Bcl(-)2 family members, suggesting that PLK1 regulates both autophagic and apoptotic responses. Taken together, our data point toward a previously unrecognized role of PLK1 on the survival of cells with mTORC1 hyperactivation, and the potential use of PLK1 inhibitors as novel therapeutics for tumors with dysregulated mTORC1 signaling, including TSC and LAM.
雷帕霉素靶蛋白复合物1（mTORC1）可促进翻译、增大细胞体积并促进血管生成，同时抑制自噬。mTORC1受错构瘤蛋白和结节性硬化蛋白的负调控，这两种蛋白是肿瘤抑制因子TSC1和TSC2的产物，在结节性硬化症（TSC）和散发性淋巴管平滑肌瘤病（LAM）中发生突变。错构瘤蛋白与中心体及有丝分裂激酶波罗样激酶1（PLK1）相互作用。缺乏错构瘤蛋白和结节性硬化蛋白的细胞在中心体复制、有丝分裂进程和胞质分裂方面存在异常，这表明错构瘤蛋白/结节性硬化蛋白异二聚体和mTORC1信号传导参与了中心体生物学和有丝分裂过程。在此我们报告，在缺乏错构瘤蛋白和结节性硬化蛋白的细胞以及LAM患者来源的标本中，PLK1蛋白水平升高，且这种升高对雷帕霉素敏感。小分子抑制剂BI-2536对PLK1的药理抑制作用显著降低了缺乏错构瘤蛋白和结节性硬化蛋白的细胞的活力和克隆形成存活率，这与细胞凋亡增加有关。BI-2536增加了p62、LC3B-I和GFP-LC3斑点，并抑制了HBSS诱导的p62降解，表明抑制PLK1可减弱自噬。最后，抑制PLK1可抑制关键自噬基因和蛋白的表达及蛋白水平，以及Bcl(-)2家族成员的蛋白水平，这表明PLK1可调节自噬和凋亡反应。综上所述，我们的数据表明PLK1在mTORC1过度激活的细胞存活中具有此前未被认识到的作用，并且PLK1抑制剂有可能作为治疗mTORC1信号失调肿瘤（包括TSC和LAM）的新型疗法。
