Chen Kuchuan, Lin Guang, Haelterman Nele A, Ho Tammy Szu-Yu, Li Tongchao, Li Zhihong, Duraine Lita, Graham Brett H, Jaiswal Manish, Yamamoto Shinya, Rasband Matthew N, Bellen Hugo J
Program in Developmental Biology, Baylor College of Medicine, Houston, United States.
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, United States.
Elife. 2016 Jun 25;5:e16043. doi: 10.7554/eLife.16043.
Mutations in Frataxin (FXN) cause Friedreich's ataxia (FRDA), a recessive neurodegenerative disorder. Previous studies have proposed that loss of FXN causes mitochondrial dysfunction, which triggers elevated reactive oxygen species (ROS) and leads to the demise of neurons. Here we describe a ROS independent mechanism that contributes to neurodegeneration in fly FXN mutants. We show that loss of frataxin homolog (fh) in Drosophila leads to iron toxicity, which in turn induces sphingolipid synthesis and ectopically activates 3-phosphoinositide dependent protein kinase-1 (Pdk1) and myocyte enhancer factor-2 (Mef2). Dampening iron toxicity, inhibiting sphingolipid synthesis by Myriocin, or reducing Pdk1 or Mef2 levels, all effectively suppress neurodegeneration in fh mutants. Moreover, increasing dihydrosphingosine activates Mef2 activity through PDK1 in mammalian neuronal cell line suggesting that the mechanisms are evolutionarily conserved. Our results indicate that an iron/sphingolipid/Pdk1/Mef2 pathway may play a role in FRDA.
弗里德赖希共济失调蛋白(FXN)的突变会导致弗里德赖希共济失调(FRDA),这是一种隐性神经退行性疾病。先前的研究表明,FXN的缺失会导致线粒体功能障碍,进而引发活性氧(ROS)水平升高并导致神经元死亡。在此,我们描述了一种不依赖ROS的机制,该机制在果蝇FXN突变体的神经退行性变中起作用。我们发现,果蝇中弗里德赖希共济失调蛋白同源物(fh)的缺失会导致铁毒性,进而诱导鞘脂合成并异位激活3-磷酸肌醇依赖性蛋白激酶-1(Pdk1)和肌细胞增强因子2(Mef2)。减轻铁毒性、用鞘氨醇霉素抑制鞘脂合成或降低Pdk1或Mef2水平,均可有效抑制fh突变体中的神经退行性变。此外,在哺乳动物神经元细胞系中,增加二氢鞘氨醇可通过PDK1激活Mef2活性,这表明该机制在进化上是保守的。我们的结果表明,铁/鞘脂/Pdk1/Mef2通路可能在FRDA中起作用。