保持线粒体完整性对于维持细胞稳态至关重要。线粒体自噬是线粒体特异性的自噬类型,可消除受损的线粒体,从而有助于线粒体质量控制。线粒体膜电位的去极化是诱导线粒体自噬的既定机制,通过 PINK1 稳定和 Parkin 募集到线粒体来介导。己糖激酶-II (HK-II) 催化葡萄糖代谢的第一步,也可作为调节细胞存活的信号分子,并且细胞 HK-II 的很大一部分与线粒体 (mitoHK-II) 相关。我们在此证明,降低 mitoHK-II 水平的 mitoHK-II 解离肽的药理干预和腺病毒表达会导致心肌细胞和人胶质母细胞瘤细胞系 1321N1 中线粒体 Parkin 和线粒体蛋白泛素化的大幅增加,而与线粒体膜去极化无关或 PINK1 累积。使用 Mito-Keima 在心肌细胞和 1321N1 细胞中证明了 MitoHK-II 解离诱导的线粒体自噬。使心肌细胞或体内心脏缺血导致 mitoHK-II 适度解离。 mitoHK-II 解离肽的表达增强了这种反应,从而增加了 Parkin 向线粒体的募集,重要的是,提供了针对缺血应激的心脏保护作用。这些结果表明 mitoHK-II 解离是由缺血应激诱导的生理相关细胞事件,其增强可防止缺血损伤。 mitoHK-II 解离作用的机制可归因于 Bcl2 相关的 athanogene 5 (BAG5)(一种 Parkin 抑制剂)定位于线粒体并与 HK-II 形成分子复合物的能力。 BAG5 的过度表达减弱,而 BAG5 的敲低则使 mitoHK-II 解离对线粒体自噬的影响敏感。我们认为HK-II是一种糖酵解分子,可以作为线粒体代谢紊乱的传感器来触发线粒体自噬,并且调节HK-II的细胞内定位可能是调节线粒体自噬以防止缺血应激诱导的细胞死亡的一种新方法。
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Dissociation of mitochondrial HK-II elicits mitophagy and confers cardioprotection against ischemia.
Preservation of mitochondrial integrity is critical for maintaining cellular homeostasis. Mitophagy is a mitochondria-specific type of autophagy which eliminates damaged mitochondria thereby contributing to mitochondrial quality control. Depolarization of the mitochondrial membrane potential is an established mechanism for inducing mitophagy, mediated through PINK1 stabilization and Parkin recruitment to mitochondria. Hexokinase-II (HK-II) which catalyzes the first step in glucose metabolism, also functions as a signaling molecule to regulate cell survival, and a significant fraction of cellular HK-II is associated with mitochondria (mitoHK-II). We demonstrate here that pharmacological interventions and adenoviral expression of a mitoHK-II dissociating peptide which reduce mitoHK-II levels lead to robust increases in mitochondrial Parkin and ubiquitination of mitochondrial proteins in cardiomyocytes and in a human glioblastoma cell line 1321N1, independent of mitochondrial membrane depolarization or PINK1 accumulation. MitoHK-II dissociation-induced mitophagy was demonstrated using Mito-Keima in cardiomyocytes and in 1321N1 cells. Subjecting cardiomyocytes or the in vivo heart to ischemia leads to modest dissociation of mitoHK-II. This response is potentiated by expression of the mitoHK-II dissociating peptide, which increases Parkin recruitment to mitochondria and, importantly, provides cardioprotection against ischemic stress. These results suggest that mitoHK-II dissociation is a physiologically relevant cellular event that is induced by ischemic stress, the enhancement of which protects against ischemic damage. The mechanism which underlies the effects of mitoHK-II dissociation can be attributed to the ability of Bcl2-associated athanogene 5 (BAG5), an inhibitor of Parkin, to localize to mitochondria and form a molecular complex with HK-II. Overexpression of BAG5 attenuates while knockdown of BAG5 sensitizes the effect of mitoHK-II dissociation on mitophagy. We suggest that HK-II, a glycolytic molecule, can function as a sensor for metabolic derangements at mitochondria to trigger mitophagy, and modulating the intracellular localization of HK-II could be a novel way of regulating mitophagy to prevent cell death induced by ischemic stress.