Aims Heart failure due to ischaemic heart disease (IHD) is a leading cause of mortality worldwide. A major contributing factor to IHD-induced cardiac damage is hypoxia. Sequestosome 1 (p62) is a multi-functional adaptor protein with pleiotropic roles in autophagy, proteostasis, inflammation, and cancer. Despite abundant expression in cardiomyocytes, the role of p62 in cardiac physiology is not well understood. We hypothesized that cardiomyocyte-specific p62 deletion evokes hypoxia-induced cardiac pathology by impairing hypoxia-inducible factor 1α (Hif-1α) and nuclear factor erythroid 2-related factor 2 (Nrf2) signalling. Methods and results Adult mice with germline deletion of cardiomyocyte p62 exhibited mild cardiac dysfunction under normoxic conditions. Transcriptomic analyses revealed a selective impairment in Nrf2 target genes in the hearts from these mice. Demonstrating the functional importance of this adaptor protein, adult mice with inducible depletion of cardiomyocyte p62 displayed hypoxia-induced contractile dysfunction, oxidative stress, and cell death. Mechanistically, p62-depleted hearts exhibit impaired Hif-1α and Nrf2 transcriptional activity. Because findings from these two murine models suggested a cardioprotective role for p62, mechanisms were evaluated using H9c2 cardiomyoblasts. Loss of p62 in H9c2 cells exposed to hypoxia reduced Hif-1α and Nrf2 protein levels. Further, the lack of p62 decreased Nrf2 protein expression, nuclear translocation, and transcriptional activity. Repressed Nrf2 activity associated with heightened Nrf2-Keap1 co-localization in p62-deficient cells, which was concurrent with increased Nrf2 ubiquitination facilitated by the E3 ligase Cullin 3, followed by proteasomal-mediated degradation. Substantiating our results, a gain of p62 in H9c2 cells stabilized Nrf2 and increased the transcriptional activity of Nrf2 downstream targets. Conclusion Cardiac p62 mitigates hypoxia-induced cardiac dysfunction by stabilizing Hif-1α and Nrf2.

中文翻译：

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Sequestosome 1 (p62) 通过稳定缺氧诱导因子 1α 和核因子红细胞 2 相关因子 2 减轻缺氧引起的心功能障碍

目标 缺血性心脏病 (IHD) 引起的心力衰竭是全世界死亡的主要原因。 IHD 引起的心脏损伤的一个主要因素是缺氧。 Sequestosome 1 (p62) 是一种多功能衔接蛋白，在自噬、蛋白质稳态、炎症和癌症中具有多效性作用。尽管 p62 在心肌细胞中大量表达，但 p62 在心脏生理学中的作用尚不清楚。我们假设心肌细胞特异性 p62 缺失通过损害缺氧诱导因子 1α (Hif-1α) 和核因子红细胞 2 相关因子 2 (Nrf2) 信号传导来诱发缺氧诱导的心脏病理学。方法和结果 心肌细胞 p62 种系缺失的成年小鼠在常氧条件下表现出轻度心功能障碍。转录组分析揭示了这些小鼠心脏中 Nrf2 靶基因的选择性损伤。诱导性耗尽心肌细胞 p62 的成年小鼠表现出缺氧诱导的收缩功能障碍、氧化应激和细胞死亡，这证明了这种接头蛋白的功能重要性。从机制上讲，p62 耗尽的心脏表现出 Hif-1α 和 Nrf2 转录活性受损。由于这两个小鼠模型的研究结果表明 p62 具有心脏保护作用，因此使用 H9c2 成肌细胞评估了其机制。暴露于缺氧的 H9c2 细胞中 p62 的缺失降低了 Hif-1α 和 Nrf2 蛋白水平。此外，p62 的缺乏会降低 Nrf2 蛋白的表达、核转位和转录活性。 Nrf2 活性受到抑制，与 p62 缺陷细胞中 Nrf2-Keap1 共定位增强相关，同时 E3 连接酶 Cullin 3 促进 Nrf2 泛素化增加，随后发生蛋白酶体介导的降解。 H9c2 细胞中 p62 的增加稳定了 Nrf2 并增加了 Nrf2 下游靶标的转录活性，这证实了我们的结果。结论 Cardiac p62通过稳定Hif-1α和Nrf2减轻缺氧引起的心功能障碍。