Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15213.
Department of Environmental and Occupational Health and Center for Free Radical and Antioxidant Health, University of Pittsburgh, Pittsburgh, PA 15213.
Nat Cell Biol. 2013 Oct;15(10):1197-1205. doi: 10.1038/ncb2837. Epub 2013 Sep 15.
Recognition of injured mitochondria for degradation by macroautophagy is essential for cellular health, but the mechanisms remain poorly understood. Cardiolipin is an inner mitochondrial membrane phospholipid. We found that rotenone, staurosporine, 6-hydroxydopamine and other pro-mitophagy stimuli caused externalization of cardiolipin to the mitochondrial surface in primary cortical neurons and SH-SY5Y cells. RNAi knockdown of cardiolipin synthase or of phospholipid scramblase-3, which transports cardiolipin to the outer mitochondrial membrane, decreased the delivery of mitochondria to autophagosomes. Furthermore, we found that the autophagy protein microtubule-associated-protein-1 light chain 3 (LC3), which mediates both autophagosome formation and cargo recognition, contains cardiolipin-binding sites important for the engulfment of mitochondria by the autophagic system. Mutation of LC3 residues predicted as cardiolipin-interaction sites by computational modelling inhibited its participation in mitophagy. These data indicate that redistribution of cardiolipin serves as an 'eat-me' signal for the elimination of damaged mitochondria from neuronal cells.
受损线粒体通过巨自噬进行降解的识别对于细胞健康至关重要，但相关机制仍知之甚少。心磷脂是一种线粒体内膜磷脂。我们发现，鱼藤酮、星形孢菌素、6-羟多巴胺和其他促进自噬的刺激物会导致原代皮质神经元和 SH-SY5Y 细胞中线粒体心磷脂外排在线粒体表面。心磷脂合酶或磷脂翻转酶-3（将心磷脂转运到线粒体外膜）的 RNAi 敲低会减少线粒体向自噬体的传递。此外，我们发现自噬蛋白微管相关蛋白 1 轻链 3（LC3），它介导自噬体的形成和货物识别，含有对于自噬系统吞噬线粒体至关重要的心磷脂结合位点。通过计算建模预测的 LC3 残基与心磷脂相互作用位点的突变会抑制其参与线粒体自噬。这些数据表明，心磷脂的重分布可作为一种“吃我”信号，将受损线粒体从神经元细胞中清除。
