MG53, A Novel Regulator of KChIP2 and Ito,f, Plays a Critical Role in Electrophysiological Remodeling in Cardiac Hypertrophy
MG53, A Novel Regulator of KChIP2 and Ito,f, Plays a Critical Role in Electrophysiological Remodeling in Cardiac Hypertrophy
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MG53 是 KChIP2 和 I-to,I-f 的新型调节因子，在心脏肥大的电生理重塑中发挥关键作用
DOI：
10.1161/circulationaha.118.029413
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发表时间：
2019-04-30
期刊：
影响因子：
37.8
通讯作者：
Liu, Jie
中科院分区：
文献类型：
--
作者：
Liu, Wenjuan;Wang, Gang;Liu, Jie
背景：KChIP2（钾离子通道相互作用蛋白）是心脏快速瞬时外向钾电流（Ito,f）的辅助亚基，KChIP2表达不足会导致心脏肥厚时Ito,f下调并引发心律失常。研究表明，肌肉特异性蛋白三光蛋白53（MG53）在正常和患病心脏中具有多种功能。本研究旨在探讨心肌MG53在调节KChIP2表达、Ito,f以及心脏肥厚时致心律失常潜能方面可能发挥的作用。
方法：通过基因敲除小鼠体内的MG53，以及在培养的新生大鼠心室肌细胞中利用腺病毒过表达或RNA干扰技术敲低MG53，来调控MG53的表达。采用苯肾上腺素刺激新生大鼠心室肌细胞诱导心肌细胞肥大，通过腹主动脉缩窄术构建压力超负荷诱导的小鼠心脏肥厚模型。
结果：在MG53基因敲除小鼠的心脏以及MG53敲低的新生大鼠心室肌细胞中，KChIP2表达和Ito,f密度下调，而在MG53过表达的细胞中则上调。在苯肾上腺素诱导的心肌细胞肥大过程中，MG53表达降低，同时KChIP2和Ito,f下调，这种情况可通过MG53过表达得到逆转，但MG53敲低会使其加剧。MG53基因敲除增强了小鼠心脏肥厚时Ito,f重塑和动作电位时程延长，增加了对室性心律失常的易感性。从机制上讲，MG53调节NF-κB（活化B细胞的核因子κ轻链增强子）活性，进而控制KChIP2的转录。染色质免疫沉淀实验表明，NF-κB蛋白与KChIP2基因存在相互作用。MG53过表达减少，而MG53敲低增加了NF-κB在KChIP2基因5'调控区的富集。使NF-κB活性恢复正常可逆转MG53过表达或敲低细胞中KChIP2的改变。免疫共沉淀和蛋白质免疫印迹分析表明，MG53与TAK1（转化生长因子-β [TGF-β] 激活激酶1）和IκBα（B细胞中κ轻链多肽基因增强子的核因子抑制剂α）存在物理相互作用，而这两者是NF-κB信号通路的关键组成部分。
结论：这些研究结果表明，MG53通过调节NF-κB活性，成为KChIP2和Ito,f的新型调节因子，并揭示了其在心脏肥厚电生理重塑中的关键作用。
BACKGROUND: KChIP2 (K+ channel interacting protein) is the auxiliary subunit of the fast transient outward K+ current (I to, f) in the heart, and insufficient KChIP2 expression induces I to, f downregulation and arrhythmogenesis in cardiac hypertrophy. Studies have shown musclespecific mitsugumin 53 (MG53) has promiscuity of function in the context of normal and diseased heart. This study investigates the possible roles of cardiac MG53 in regulation of KChIP2 expression and I to, f, and the arrhythmogenic potential in hypertrophy. METHODS: MG53 expression is manipulated by genetic ablation of MG53 in mice and adenoviral overexpression or knockdown of MG53 by RNA interference in cultured neonatal rat ventricular myocytes. Cardiomyocyte hypertrophy is produced by phenylephrine stimulation in neonatal rat ventricular myocytes, and pressure overload-induced mouse cardiac hypertrophy is produced by transverse aortic constriction. RESULTS: KChIP2 expression and I to, f density are downregulated in hearts from MG53-knockout mice and MG53-knockdown neonatal rat ventricular myocytes, but upregulated in MG53-overexpressing cells. In phenylephrine-induced cardiomyocyte hypertrophy, MG53 expression is reduced with concomitant downregulation of KChIP2 and I to, f, which can be reversed by MG53 overexpression, but exaggerated by MG53 knockdown. MG53 knockout enhances I to, f remodeling and action potential duration prolongation and increases susceptibility to ventricular arrhythmia in mouse cardiac hypertrophy. Mechanistically, MG53 regulates NF-.B (nuclear factor kappa-light-chain-enhancer of activated B cells) activity and subsequently controls KChIP2 transcription. Chromatin immunoprecipitation demonstrates NF-.B protein has interaction with KChIP2 gene. MG53 overexpression decreases, whereas MG53 knockdown increases NF-.B enrichment at the 5' regulatory region of KChIP2 gene. Normalizing NF-.B activity reverses the alterations in KChIP2 in MG53-overexpressing or knockdown cells. Coimmunoprecipitation and Western blotting assays demonstrate MG53 has physical interaction with TAK1 (transforming growth factor-b [ TGFb]-activated kinase 1) and I.Ba (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha), critical components of the NF-.B pathway. CONCLUSIONS: These findings establish MG53 as a novel regulator of KChIP2 and I to, f by modulating NF-.B activity and reveal its critical role in electrophysiological remodeling in cardiac hypertrophy.