Department of Anatomy, Physiology, and Genetics, Uniformed Services University for the Health Sciences, Bethesda, MD, USA.
Department of Medicine, Uniformed Services University for the Health Sciences, Bethesda, MD, USA.
Physiol Rep. 2021 Jan;8(24):e14675. doi: 10.14814/phy2.14675.
We recently discovered that the histone deacetylase inhibitor, trichostatin A (TSA), increases expression of the sulfonylurea receptor 2 (SUR2; Abcc9) subunit of the ATP-sensitive K (K ) channel in HL-1 cardiomyocytes. Interestingly, the increase in SUR2 was abolished with exogenous cholesterol, suggesting that cholesterol may regulate channel expression. In the present study, we tested the hypothesis that TSA increases SUR2 by depleting cholesterol and activating the sterol response element binding protein (SREBP) family of transcription factors. Treatment of HL-1 cardiomyocytes with TSA (30 ng/ml) caused a time-dependent increase in SUR2 mRNA expression that correlates with the time course of cholesterol depletion assessed by filipin staining. Consistent with the cholesterol-dependent regulation of SREBP increasing SUR2 mRNA expression, we observe a significant increase in SREBP cleavage and translocation to the nucleus following TSA treatment that is inhibited by exogenous cholesterol. Further supporting the role of SREBP in mediating the effect of TSA on K subunit expression, SREBP1 significantly increased luciferase reporter gene expression driven by the upstream SUR2 promoter. Lastly, HL-1 cardiomyocytes treated with the SREBP inhibitor PF429242 significantly suppresses the effect of TSA on SUR2 gene expression. These results demonstrate that SREBP is an important regulator of K channel expression and suggest a novel method by which hypercholesterolemia may exert negative effects on the cardiovascular system, namely, by suppressing expression of the K channel.
我们最近发现，组蛋白去乙酰化酶抑制剂曲古抑菌素 A（TSA）可增加 HL-1 心肌细胞中磺酰脲受体 2（SUR2；Abcc9）亚基的 ATP 敏感性 K（K）通道表达。有趣的是，外源性胆固醇可消除 SUR2 的增加，表明胆固醇可能调节通道表达。在本研究中，我们检验了 TSA 通过耗竭胆固醇和激活固醇调节元件结合蛋白（SREBP）家族转录因子来增加 SUR2 的假说。用 TSA（30ng/ml）处理 HL-1 心肌细胞可引起 SUR2 mRNA 表达的时间依赖性增加，与 Filipin 染色评估的胆固醇耗竭过程一致。与胆固醇依赖性调节 SREBP 增加 SUR2 mRNA 表达一致，我们观察到 TSA 处理后 SREBP 切割和向核易位明显增加，外源性胆固醇可抑制其发生。进一步支持 SREBP 在介导 TSA 对 K 亚基表达的影响中的作用，SREBP1 显著增加了由 SUR2 启动子上游驱动的荧光素酶报告基因表达。最后，用 SREBP 抑制剂 PF429242 处理的 HL-1 心肌细胞可显著抑制 TSA 对 SUR2 基因表达的影响。这些结果表明 SREBP 是 K 通道表达的重要调节剂，并提示高胆固醇血症可能通过抑制 K 通道表达对心血管系统产生负面影响的新方法。
