TMEM43-S358L突变在NF-kB炎症信号通路中的功能及其对ARVD心肌病的贡献

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVD) is a genetic disorder that leads to high risk of sudden cardiac death. The hearts of ARVD patients have severe symptoms like increasing inflammation responses, cardiac fibrosis and enlarged cardiac chambers. Previous studies have identified TMEM43-Ser358Leu mutation as the cause of ARVD5, a severe ARVD subtype with high lethality and fully penetrance found in various patient families in different countries. NF-kB is a family of transcription factors, which plays essential roles in inflammation, and is activated in various human chronic inflammatory diseases. Using a Bimolecular Fluorescence Complementation (BiFC)-based functional genomics screening, we identified TMEM43 as a key component in GPCR-induced NF-kB activation. We found that TMEM43-S358L mutant enhanced GPCR-induced NF-kB activation and the expression of cardiac fibrosis genes. Therefore, we propose that TMEM43 S358L mutation activates NF-kB signaling and inflammation, thereby contributes to ARVD pathogenesis. We have generated a TMEM43-S358L knock-in mouse strain, and established Angiotensin II infusion mouse model to investigate the contributions of TMEM43-S358L to ARVD pathogenesis, and apply NF-kB-GFP transgenic mouse，IKK beta-cardiac specific knockout mouse for NF-kB signaling deficiency to study the roles of NF-kB inflammation signaling in ARVD. Our study will provide the genetic evidence linking chronic inflammation to ARVD cardiomyopathy, and provide the molecular insight for designing anti-inflammation therapeutic agents for treatment of ARVD patients.

致心率失常性心肌病(ARVD)是致心脏猝死的高风险显性遗传病，具有炎症活性增强、心脏纤维化等症状。在严重的高死亡率、完全外显的ARVD亚型ARVD5的多个病人家族中，已经鉴定出了同样的TMEM43-S358L突变。NF-kB信号在炎症反应中起基础性作用。通过生物分子荧光互补筛选，我们鉴定出TMEM43是NF-kB信号激活的关键元件。在心肌细胞中TMEM43-S358L突变增强GPCR介导的NF-kB信号和心脏纤维化基因表达。因此，我们假设：TMEM43-S358L突变通过激活NF-kB信号引起炎症反应从而导致ARVD的病理发生。本项目将应用TMEM43-S358L、IKKβ心脏特异性敲除和血管紧张素2灌流等小鼠模型来研究TMEM43-S358L突变及其诱导的NF-kB炎症反应对ARVD病理的贡献。该研究将建立炎症反应与ARVD心肌病之间的有机联系，为该疾病进行抗炎症治疗和新药开发提供基础。

致心率失常性心肌病(ARVD)是一种导致心脏性猝死的高风险遗传性疾病。在不同国家的多个ARVD5病人家族中一种严重的高死亡率和完全外显的ARVD亚型，已经鉴定出了共同的TMEM43-S358L遗传突变。在我们构建的相同突变小鼠中也发现部分ARVD病征如心脏纤维化和脂肪化、心腔变大等。 RNA-seq分析说明纤维化信号通路TGFβ，脂肪化信号通路PPARγ在TMEM43-S358L小鼠心脏中显著增强。有报道NFκB信号与心脏纤维化过程相关。我们发现TMEM43是NFκB信号激活所必需的，在心肌细胞中TMEM43-S358L突变体显著增强NFκB炎症信号活性和心肌纤维化。启动子预测发现TGFβ1启动子上有保守的NFκB结合位点，实验验证其转录激活受NFκB直接调控。免疫共沉淀质谱分析发现TMEM43在S358L突变后与PPARγ共激活因子CCPG的结合变强，并调控PPARγ信号下游基因PLIN和ADIPOQ的转录活性。因此，我们得出结论：TMEM43-S358L基因突变通过NFκB-TGFβ信号流引起心脏纤维化，通过CCPG提高PPARγ信号加速脂肪化从而加速ARVD的病理发生。此项研究将建立炎症反应与ARVD心肌病之间的有机联系，为该疾病进行抗炎症治疗和新药开发提供基础。