Cai Sidong, Liu Rong, Wang Panxia, Li Jingyan, Xie Tingting, Wang Minghui, Cao Yanjun, Li Zhuoming, Liu Peiqing
Laboratory of Pharmacology and Toxicology, School of Pharmaceutical Sciences, National and Local United Engineering Lab of Druggability and New Drugs Evaluation, Guangdong Engineering Laboratoty of Druggability and New Drug Evaluation, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Higher Education Mega Center, Sun Yat-Sen University, Guangzhou, China.
Obstetrical Department, Guangzhou Clifford Hospital, Guangzhou, China.
Front Pharmacol. 2020 Dec 10;11:600627. doi: 10.3389/fphar.2020.600627. eCollection 2020.
The present study reveals a link between protein arginine methyltransferase 5 (PRMT5) and Homebox A9 (HoxA9) in the regulation of cardiomyocyte hypertrophy. In cardiomyocyte hypertrophy induced by β-adrenergic receptor agonist isoprenaline (ISO), PRMT5 expression was decreased while HoxA9 was upregulated. Silencing of PRMT5 or inhibition of PRMT5 by its pharmacological inhibitor EPZ augmented the expressions of cardiomyocyte hypertrophic genes brain natriuretic peptide (BNP) and β-Myosin Heavy Chain (β-MHC), whereas overexpression of PRMT5 inhibited ISO-induced cardiomyocyte hypertrophy, suggesting that PRMT5 ameliorates cardiomyocyte hypertrophy. On the contrary, HoxA9 promoted cardiomyocyte hypertrophy, as implied by the gain-of-function and loss-of-function experiments. HoxA9 was involved in the regulation of PRMT5 in cardiomyocyte hypertrophy, since HoxA9 knockdown prevented si-RPMT5-induced cardiomyocyte hypertrophy, and HoxA9 expression impaired the anti-hypertrophic effect of PRMT5. Co-immunoprecipitation experiments revealed that there were physical interactions between PRMT5 and HoxA9. The symmetric dimethylation level of HoxA9 was decreased by ISO or EPZ treatment, suggesting that HoxA9 is methylated by PRMT5. Additionally, PRMT5 repressed the expression of HoxA9. Chromatin immunoprecipitation (ChIP) assay demonstrated that HoxA9 could bind to the promoter of BNP, and that this binding affinity was further enhanced by ISO or EPZ. In conclusion, this study suggests that PRMT5 symmetric dimethylates HoxA9 and represses HoxA9 expression, thus impairing its binding to BNP promoter and ultimately protecting against cardiomyocyte hypertrophy. These findings provide a novel insight of the mechanism underlying the cardiac protective effect of PRMT5, and suggest potential therapeutic strategies of PRMT5 activation or HoxA9 inhibition in treatment of cardiac hypertrophy.
本研究揭示了蛋白质精氨酸甲基转移酶5（PRMT5）与同源框A9（HoxA9）在心肌细胞肥大调节中的联系。在β-肾上腺素能受体激动剂异丙肾上腺素（ISO）诱导的心肌细胞肥大中，PRMT5表达降低而HoxA9上调。PRMT5沉默或其药理学抑制剂EPZ对PRMT5的抑制增强了心肌细胞肥大相关基因脑钠肽（BNP）和β-肌球蛋白重链（β-MHC）的表达，而PRMT5过表达则抑制ISO诱导的心肌细胞肥大，提示PRMT5可改善心肌细胞肥大。相反，功能获得和功能丧失实验表明HoxA9促进心肌细胞肥大。HoxA9参与心肌细胞肥大中PRMT5的调节，因为HoxA9敲低可阻止si-RPMT5诱导的心肌细胞肥大，且HoxA9表达削弱了PRMT5的抗肥大作用。免疫共沉淀实验显示PRMT5与HoxA9之间存在物理相互作用。ISO或EPZ处理降低了HoxA9的对称二甲基化水平，提示HoxA9被PRMT5甲基化。此外，PRMT5抑制HoxA9的表达。染色质免疫沉淀（ChIP）分析表明HoxA9可结合BNP启动子，且ISO或EPZ可进一步增强这种结合亲和力。总之，本研究提示PRMT5使HoxA9对称二甲基化并抑制HoxA9表达，从而削弱其与BNP启动子的结合，最终预防心肌细胞肥大。这些发现为PRMT5心脏保护作用的潜在机制提供了新见解，并提示PRMT5激活或HoxA9抑制在治疗心脏肥大中的潜在治疗策略。
