Southern Alberta Cancer Research Institute, Department of Biochemistry and Molecular Biology, University of Calgary, Alberta, Canada.
Int J Biochem Cell Biol. 2012 Aug;44(8):1366-76. doi: 10.1016/j.biocel.2012.05.004. Epub 2012 May 15.
Mitochondrial morphology is dynamic and controlled by coordinated fusion and fission pathways. The role of mitochondrial chaperones in mitochondrial morphological changes and pathology is currently unclear. Here we report that altered levels of DnaJA3 (Tid1/mtHsp40) a mitochondrial member of the DnaJ protein family, and heat shock protein (Hsp) co-chaperone of matrix 70 kDa Hsp70 (mtHsp70/mortalin/HSPA9), induces mitochondrial fragmentation. Suppression of DnaJA3 induced mitochondrial fragmentation in HeLa cells. Elevated levels of DnaJA3 in normal Hs68 fibroblast cells and HeLa, SKN-SH, U87 and U251 cancer cell lines induces mitochondrial fragmentation. Mitochondrial fragmentation induction was not observed in HeLa cells when other DnaJA family members, or mitochondrial DnaJ protein HSC20, were ectopically expressed, indicating that the effects on mitochondrial morphology were specific to DnaJA3. We show that the DnaJ domain (amino acids 88-168) of DnaJA3 is sufficient for the induction of mitochondrial fragmentation. Furthermore, an H121Q point mutation of the DnaJ domain, which abrogates interaction and activation of mtHsp70 ATPase, eliminates fragmentation induced by DnaJA3. This suggests that DnaJA3 interaction with mtHsp70 may be critical in mitochondrial morphological changes. DnaJA3-induced mitochondrial fragmentation was dependent on fission factor dynamin-related protein 1 (Drp1). Ectopic expression of the mitofusins (Mfn1 and Mfn2), however, does not rescue DnaJA3-induced mitochondrial fragmentation. Lastly, elevated levels of DnaJA3 inducing mitochondrial fragmentation were associated with reduction in cell viability. Taken together, elevated DnaJA3 induces Drp1-depedendent mitochondrial fragmentation and decreased cell viability.
线粒体形态是动态的，并受协调融合和裂变途径的控制。线粒体伴侣蛋白在线粒体形态变化和病理学中的作用目前尚不清楚。在这里，我们报告说，改变线粒体 DnaJA3（Tid1/mtHsp40）的水平，一种线粒体 DnaJ 蛋白家族成员，以及基质 70 kDa Hsp70（mtHsp70/mortalin/HSPA9）的热休克蛋白（Hsp）共伴侣，会诱导线粒体碎片化。DnaJA3 的抑制会诱导 HeLa 细胞中的线粒体碎片化。在正常的 Hs68 成纤维细胞和 HeLa、SKN-SH、U87 和 U251 癌细胞系中，DnaJA3 水平的升高会诱导线粒体碎片化。当其他 DnaJA 家族成员或线粒体 DnaJ 蛋白 HSC20 异位表达时，在 HeLa 细胞中没有观察到线粒体碎片化的诱导，这表明对线粒体形态的影响是特异性的 DnaJA3。我们表明 DnaJA3 的 DnaJ 结构域（氨基酸 88-168）足以诱导线粒体碎片化。此外，DnaJ 结构域的 H121Q 点突变，消除了 DnaJA3 诱导的碎片化，该突变消除了与 mtHsp70 ATP 酶的相互作用和激活。这表明 DnaJA3 与 mtHsp70 的相互作用可能在线粒体形态变化中至关重要。DnaJA3 诱导的线粒体碎片化依赖于分裂因子 dynamin 相关蛋白 1（Drp1）。然而，过表达线粒体融合蛋白（Mfn1 和 Mfn2）并不能挽救 DnaJA3 诱导的线粒体碎片化。最后，诱导线粒体碎片化的 DnaJA3 水平升高与细胞活力降低有关。总之，升高的 DnaJA3 诱导 Drp1 依赖性线粒体碎片化和降低细胞活力。
