Calreticulin Regulates Transforming Growth Factor-β-stimulated Extracellular Matrix Production*
Calreticulin Regulates Transforming Growth Factor-β-stimulated Extracellular Matrix Production*
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DOI：
10.1074/jbc.m112.447243
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发表时间：
2013-04
期刊：
影响因子：
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通讯作者：
Kurt A. Zimmerman;Lauren Graham;M. Pallero;J. Murphy-Ullrich
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文献类型：
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作者：
Kurt A. Zimmerman;Lauren Graham;M. Pallero;J. Murphy-Ullrich
背景：内质网（ER）应激与纤维化疾病有关，尽管其机制尚不完全清楚。结果如下：ER应激蛋白钙网蛋白通过控制细胞内钙和NFAT信号传导来调节TGF-β刺激的细胞外基质。结论：钙网蛋白是TGF-β刺激细胞外基质生成所必需的。意义：这些发现确定钙网蛋白作为ER应激和纤维化之间的机制联系。内质网（ER）应激是纤维化疾病中的一个新兴因素，尽管确切的机制尚不清楚。钙网蛋白（CRT）是一种ER伴侣和钙离子信号的调节剂上调的ER应激和纤维化组织。以前，我们表明，ER CRT调节I型胶原蛋白的转录，运输，分泌和加工成细胞外基质（ECM）。为了确定CRT在纤维化条件下ECM调节中的作用，我们询问CRT是否改变了对促纤维化细胞因子TGF-β的细胞应答。这些研究表明，CRT-/-小鼠胚胎成纤维细胞（MEF）和大鼠和人类特发性肺纤维化肺成纤维细胞与siRNA CRT敲低受损的TGF-β刺激I型胶原和纤连蛋白。相反，CRT表达增加的成纤维细胞对TGF-β的反应增强。CRT的缺乏不会影响典型的TGF-β信号传导，因为TGF-β能够刺激CRT−/− MEFs中的Smad报告基因活性。CRT调节TGF-β刺激的Ca 2+信号对于ECM的诱导是重要的。CRT−/− MEFs未能响应TGF-β增加细胞内Ca 2+水平。NFAT活性是TGF-β刺激ECM所必需的。在CRT−/− MEFs中，NFAT核转位和报告基因活性的TGF-β刺激受损。重要的是，CRT是在ER应激条件下TGF-β刺激ECM所必需的，因为衣霉素诱导的ER应激不足以诱导TGF-β刺激的CRT−/− MEFs中的ECM产生。总之，这些数据将CRT调节的Ca 2+依赖性途径确定为ER应激和TGF-β纤维化信号传导之间的关键分子联系。
Background: Endoplasmic reticulum (ER) stress is associated with fibrotic diseases, although the mechanisms are not completely understood. Results: The ER stress protein calreticulin regulates TGF-β stimulated extracellular matrix through control of intracellular calcium and NFAT signaling. Conclusion: Calreticulin is necessary for TGF-β stimulated extracellular matrix production. Significance: These findings identify calreticulin as a mechanistic link between ER stress and fibrosis. Endoplasmic reticulum (ER) stress is an emerging factor in fibrotic disease, although precise mechanisms are not clear. Calreticulin (CRT) is an ER chaperone and regulator of Ca2+ signaling up-regulated by ER stress and in fibrotic tissues. Previously, we showed that ER CRT regulates type I collagen transcript, trafficking, secretion, and processing into the extracellular matrix (ECM). To determine the role of CRT in ECM regulation under fibrotic conditions, we asked whether CRT modified cellular responses to the pro-fibrotic cytokine, TGF-β. These studies show that CRT−/− mouse embryonic fibroblasts (MEFs) and rat and human idiopathic pulmonary fibrosis lung fibroblasts with siRNA CRT knockdown had impaired TGF-β stimulation of type I collagen and fibronectin. In contrast, fibroblasts with increased CRT expression had enhanced responses to TGF-β. The lack of CRT does not impact canonical TGF-β signaling as TGF-β was able to stimulate Smad reporter activity in CRT−/− MEFs. CRT regulation of TGF-β-stimulated Ca2+ signaling is important for induction of ECM. CRT−/− MEFs failed to increase intracellular Ca2+ levels in response to TGF-β. NFAT activity is required for ECM stimulation by TGF-β. In CRT−/− MEFs, TGF-β stimulation of NFAT nuclear translocation and reporter activity is impaired. Importantly, CRT is required for TGF-β stimulation of ECM under conditions of ER stress, as tunicamycin-induced ER stress was insufficient to induce ECM production in TGF-β stimulated CRT−/− MEFs. Together, these data identify CRT-regulated Ca2+-dependent pathways as a critical molecular link between ER stress and TGF-β fibrotic signaling.