Lee Byoungchun, Ahn Younghee, Kang Sung-Myung, Park Youngjin, Jeon You-Jin, Rho Jong M, Kim Sung-Woo
Southern Alberta Cancer Research Institute, Department of Biochemistry and Molecular Biology, Alberta Children's Hospital Research Institute for Child and Maternal Health, University of Calgary, Calgary, AB T2N 4N1, Canada.
Department of Pediatrics and Clinical Neurosciences, Alberta Children's Hospital Research Institute for Child and Maternal Health, University of Calgary, Calgary, AB T2N 4N1, Canada.
Mol Biol Cell. 2015 Jun 15;26(12):2156-67. doi: 10.1091/mbc.E14-02-0762. Epub 2015 Apr 22.
Deregulation of mitochondrial heat-shock protein 40 (mtHsp40) and dysfunction of mtHsp70 are associated with mitochondrial fragmentation, suggesting that mtHsp40 and mtHsp70 may play roles in modulating mitochondrial morphology. However, the mechanism of mitochondrial fragmentation induced by mtHsp40 deregulation and mtHsp70 dysfunction remains unclear. In addition, the functional link between mitochondrial morphology change upon deregulated mtHsp40/mtHsp70 and mitochondrial function has been unexplored. Our coimmunoprecipitation and protein aggregation analysis showed that both overexpression and depletion of mtHsp40 accumulated aggregated proteins in fragmented mitochondria. Moreover, mtHsp70 loss and expression of a mtHsp70 mutant lacking the client-binding domain caused mitochondrial fragmentation. Together the data suggest that the molecular ratio of mtHsp40 to mtHsp70 is important for their chaperone function and mitochondrial morphology. Whereas mitochondrial translocation of Drp1 was not altered, optic atrophy 1 (Opa1) short isoform accumulated in fragmented mitochondria, suggesting that mitochondrial fragmentation in this study results from aberration of mitochondrial inner membrane fusion. Finally, we found that fragmented mitochondria were defective in cristae development, OXPHOS, and ATP production. Taken together, our data suggest that impaired stoichiometry between mtHsp40 and mtHsp70 promotes Opa1L cleavage, leading to cristae opening, decreased OXPHOS, and triggering of mitochondrial fragmentation after reduction in their chaperone function.
线粒体热休克蛋白40（mtHsp40）的失调和mtHsp70的功能障碍与线粒体碎片化有关，这表明mtHsp40和mtHsp70可能在调节线粒体形态中发挥作用。然而，由mtHsp40失调和mtHsp70功能障碍诱导的线粒体碎片化机制仍不清楚。此外，mtHsp40/mtHsp70失调后线粒体形态变化与线粒体功能之间的功能联系尚未得到探索。我们的免疫共沉淀和蛋白质聚集分析表明，mtHsp40的过表达和缺失都会在碎片化的线粒体中积累聚集蛋白。此外，mtHsp70的缺失以及缺乏客户结合域的mtHsp70突变体的表达会导致线粒体碎片化。这些数据共同表明，mtHsp40与mtHsp70的分子比例对其伴侣功能和线粒体形态很重要。虽然动力相关蛋白1（Drp1）的线粒体易位没有改变，但视神经萎缩蛋白1（Opa1）短异构体在碎片化的线粒体中积累，这表明本研究中的线粒体碎片化是由线粒体内膜融合异常引起的。最后，我们发现碎片化的线粒体在嵴发育、氧化磷酸化和ATP产生方面存在缺陷。综上所述，我们的数据表明，mtHsp40和mtHsp70之间化学计量的受损促进了Opa1L的切割，导致嵴开放、氧化磷酸化降低，并在其伴侣功能降低后引发线粒体碎片化。
