Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University. Guangzhou, Guangdong 511436, PR China; Guangzhou Institute of Cardiovascular Disease, Guangzhou Key Laboratory of Cardiovascular Disease, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou 510260, PR China.
Key Laboratory of Molecular Clinical Pharmacology & Fifth Affiliated Hospital, Guangzhou Medical University. Guangzhou, Guangdong 511436, PR China.
J Mol Cell Cardiol. 2018 Nov;124:70-82. doi: 10.1016/j.yjmcc.2018.08.018. Epub 2018 Aug 23.
DRAM1 (Damage-regulated autophagy modulator 1) was reported as one of the most important lysosome membrane protein that mediates the interaction between autophagosome and lysosome. Our aim was to investigate whether DRAM1 contributes to cardiac remodeling after acute myocardial infarction (AMI) and the underlying mechanisms.
Adenovirus harboring DRAM1 was injected in the peri-infarct zone in a rat model of AMI experimentally produced by permanent ligation of left anterior descending (LAD) coronary artery. Increased DRAM1 expression protected the cardiomyocytes from ischemia stress-induced autophagy flux obstacle and improved cardiac prognosis after AMI. DRAM1 overexpression attenuated the accumulation of autophagy substrate protein, LC3IIand p62/SQSTM1 obviously both in vivo and in vitro. An adenovirus harboring mRFP-GFP-LC3 showed that DRAM1 overexpression restored the autophagic flux by enhancing autophagosome conversion to autophagolysosome. Although Atg12 mRNA was up-regulated with DRAM1 overexpression the free Atg12 protein was decreased accompanied by increased Atg12-Atg5 conjugate both in vitro and in vivo. Of interest, immunoprecipitation assay showed that DRAM1 interacted with Atg7, but without direct interaction with Atg5 or Atg12. Notably, the effect of DRAM1 on autophagy flux and cardiomyocyte protection could be mitigated by Atg7 siRNA.
Our results indicated that DRAM1 protected cardiomyocytes from ischemia stress-induced autophagy flux obstacle and uncovered a novel DRAM1-Atg7-Atg12/Atg5 autophagy flux regulation pathway under conditions of myocardial ischemic stress.
DRAM1（损伤调节自噬调节剂 1）被报道为最重要的溶酶体膜蛋白之一，介导自噬体与溶酶体之间的相互作用。我们的目的是研究 DRAM1 是否有助于急性心肌梗死（AMI）后的心脏重构以及潜在的机制。
通过永久性结扎左前降支（LAD）冠状动脉在 AMI 大鼠模型中，在梗死周边区注射携带 DRAM1 的腺病毒。DRAM1 表达增加可保护心肌细胞免受缺血应激诱导的自噬通量障碍，并改善 AMI 后的心脏预后。DRAM1 过表达明显减轻了自噬底物蛋白 LC3II 和 p62/SQSTM1 在体内和体外的积累。携带 mRFP-GFP-LC3 的腺病毒表明，DRAM1 过表达通过增强自噬体向自噬溶酶体的转化来恢复自噬通量。尽管 DRAM1 过表达上调了 Atg12 mRNA，但伴随着游离 Atg12 蛋白减少以及体内和体外 Atg12-Atg5 缀合物增加。有趣的是，免疫沉淀实验表明 DRAM1 与 Atg7 相互作用，但与 Atg5 或 Atg12 没有直接相互作用。值得注意的是，Atg7 siRNA 可减轻 DRAM1 对自噬通量和心肌细胞保护的作用。
我们的结果表明，DRAM1 可保护心肌细胞免受缺血应激诱导的自噬通量障碍，并揭示了心肌缺血应激条件下 DRAM1-Atg7-Atg12/Atg5 自噬通量调节的新途径。
