Department of Cardiology, UT M.D. Anderson Cancer Center, USA.
J Mol Cell Cardiol. 2011 Sep;51(3):337-46. doi: 10.1016/j.yjmcc.2011.05.019. Epub 2011 Jun 17.
The platelet derived growth factor receptor (PDGFR) is an important target for novel anti-cancer therapeutics, but agents targeting PDGFR have been associated with cardiotoxicity. Cardiomyocyte PDGFR-β signaling in pressure-overloaded hearts induces compensatory angiogenesis via a paracrine-signaling cascade. Tight regulation of receptor tyrosine kinases in response to ligand stimulation is a critical part of any such cascade. The objective of the present study was to characterize the early and late regulation of PDGFR-β following ligand stimulation and define a potential role for microRNAs (miRNAs) predicted to interact with the 3'UTR of PDGFR-β in feedback regulation. Using two in-vitro model systems (U87 glioblastoma cells and neonatal cardiomyocytes), we observed that in response to stimulation with PDGF-BB, levels of PDGFR-β declined beginning at one hour, persisting for 48 h. PDGFR-β mRNA levels declined beginning at 6h after receptor activation. Early, but not late activation-induced receptor downregulation was proteasome dependent. Levels of miRNA-9 (miR-9) were significantly increased in U87 cells and cardiomyocytes beginning 6h after addition of ligand. In response to pressure overload, miR-9 levels were significantly reduced in the hearts of cardiac-specific PDGFR-β knockout mice. Luciferase reporter assays demonstrate that miR-9 directly interacts with its predicted seed in the 3'UTR of PDGFR-β. Increasing miR-9 levels reduces levels of PDGFR-β, resulting in a reduction in the paracrine angiogenic capacity of cardiomyocytes, consistent with the established function of cardiomyocyte PDGFR-β. Importantly, increase of anti-miR-9 in cardiomyocytes attenuates ligand-induced PDGFR-β downregulation. In conclusion, we have identified miR-9 as an activation-induced regulator of PDGFR-β expression in cardiomyocytes that is part of a negative feedback loop which serves to modulate PDGFR-β expression upon ligand-stimulation through direct interaction with the 3'UTR of PDFGR-β. This article is part of a Special Issue entitled 'Possible Editorial'.
血小板衍生生长因子受体 (PDGFR) 是新型抗癌治疗的重要靶点，但靶向 PDGFR 的药物与心脏毒性有关。压力超负荷心脏中的心肌细胞 PDGFR-β 信号通过旁分泌信号级联诱导代偿性血管生成。配体刺激后受体酪氨酸激酶的紧密调节是任何级联反应的关键部分。本研究的目的是描述配体刺激后 PDGFR-β 的早期和晚期调节，并确定预测与 PDGFR-β 的 3'UTR 相互作用的 microRNAs (miRNAs) 在反馈调节中发挥潜在作用。使用两种体外模型系统（U87 神经胶质瘤细胞和新生心肌细胞），我们观察到，在 PDGF-BB 刺激下，PDGFR-β 的水平在一小时后开始下降，持续 48 小时。PDGFR-β mRNA 水平在受体激活后 6 小时开始下降。早期但不是晚期激活诱导的受体下调依赖于蛋白酶体。在添加配体后 6 小时，U87 细胞和心肌细胞中的 miRNA-9 (miR-9) 水平显着增加。在心脏特异性 PDGFR-β 敲除小鼠中，压力超负荷后 miR-9 水平显着降低。荧光素酶报告基因检测表明，miR-9 直接与其预测的 PDGFR-β 3'UTR 中的种子相互作用。增加 miR-9 水平会降低 PDGFR-β 水平，从而降低心肌细胞的旁分泌血管生成能力，这与心肌细胞 PDGFR-β 的既定功能一致。重要的是，心肌细胞中抗 miR-9 的增加可减轻配体诱导的 PDGFR-β 下调。总之，我们已经确定 miR-9 是心肌细胞中 PDGFR-β 表达的激活诱导调节剂，是通过与 PDGFR-β 的 3'UTR 直接相互作用来调节配体刺激后 PDGFR-β 表达的负反馈回路的一部分。本文是特刊“可能的社论”的一部分。
