Hamacher-Brady A, Brady N R, Logue S E, Sayen M R, Jinno M, Kirshenbaum L A, Gottlieb R A, Gustafsson A B
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
Cell Death Differ. 2007 Jan;14(1):146-57. doi: 10.1038/sj.cdd.4401936. Epub 2006 Apr 28.
Ischemia and reperfusion (I/R) injury is associated with extensive loss of cardiac myocytes. Bnip3 is a mitochondrial pro-apoptotic Bcl-2 protein which is expressed in the adult myocardium. To investigate if Bnip3 plays a role in I/R injury, we generated a TAT-fusion protein encoding the carboxyl terminal transmembrane deletion mutant of Bnip3 (TAT-Bnip3DeltaTM) which has been shown to act as a dominant negative to block Bnip3-induced cell death. Perfusion with TAT-Bnip3DeltaTM conferred protection against I/R injury, improved cardiac function, and protected mitochondrial integrity. Moreover, Bnip3 induced extensive fragmentation of the mitochondrial network and increased autophagy in HL-1 myocytes. 3D rendering of confocal images revealed fragmented mitochondria inside autophagosomes. Enhancement of autophagy by ATG5 protected against Bnip3-mediated cell death, whereas inhibition of autophagy by ATG5K130R enhanced cell death. These results suggest that Bnip3 contributes to I/R injury which triggers a protective stress response with upregulation of autophagy and removal of damaged mitochondria.
缺血再灌注（I/R）损伤与心肌细胞的大量丧失有关。Bnip3是一种线粒体促凋亡Bcl-2蛋白，在成年心肌中表达。为了研究Bnip3是否在I/R损伤中起作用，我们生成了一种TAT融合蛋白，其编码Bnip3的羧基末端跨膜缺失突变体（TAT-Bnip3DeltaTM），该突变体已被证明可作为显性负性蛋白来阻断Bnip3诱导的细胞死亡。用TAT-Bnip3DeltaTM灌注可保护心脏免受I/R损伤，改善心脏功能，并保护线粒体完整性。此外，Bnip3诱导HL-1心肌细胞中线粒体网络广泛断裂并增加自噬。共聚焦图像的3D渲染显示自噬体内有线粒体碎片。通过ATG5增强自噬可保护细胞免受Bnip3介导的细胞死亡，而通过ATG5K130R抑制自噬则会增强细胞死亡。这些结果表明，Bnip3促成I/R损伤，后者通过上调自噬和清除受损线粒体引发保护性应激反应。
