Read Tracy-Ann, Cisterna Bruno A, Skruber Kristen, Ahmadieh Samah, Lindamood Halli L, Vitriol Josefine A, Shi Yang, Lefebvre Austin E Y T, Black Joseph B, Butler Mitchell T, Bear James E, Cherezova Alena, Ilatovskaya Daria V, Weintraub Neil L, Vitriol Eric A
Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA.
Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA, USA.
bioRxiv. 2023 Sep 19:2023.08.07.552354. doi: 10.1101/2023.08.07.552354.
Profilin 1 (PFN1) is an actin binding protein that is vital for the polymerization of monomeric actin into filaments. Here we screened knockout cells for novel functions of PFN1 and discovered that mitophagy, a type of selective autophagy that removes defective or damaged mitochondria from the cell, was significantly upregulated in the absence of PFN1. Despite successful autophagosome formation and fusion with the lysosome, and activation of additional mitochondrial quality control pathways, PFN1 knockout cells still accumulate damaged, dysfunctional mitochondria. Subsequent imaging and functional assays showed that loss of PFN1 significantly affects mitochondria morphology, dynamics, and respiration. Further experiments revealed that PFN1 is located to the mitochondria matrix and is likely regulating mitochondria function from within rather than through polymerizing actin at the mitochondria surface. Finally, PFN1 mutants associated with amyotrophic lateral sclerosis (ALS) fail to rescue PFN1 knockout mitochondrial phenotypes and form aggregates within mitochondria, further perturbing them. Together, these results suggest a novel function for PFN1 in regulating mitochondria and identify a potential pathogenic mechanism of ALS-linked PFN1 variants.
丝切蛋白1（PFN1）是一种肌动蛋白结合蛋白，对单体肌动蛋白聚合成丝至关重要。在此，我们对基因敲除细胞进行筛选以寻找PFN1的新功能，发现线粒体自噬（一种从细胞中清除有缺陷或受损线粒体的选择性自噬类型）在缺乏PFN1时显著上调。尽管自噬体成功形成并与溶酶体融合，且其他线粒体质量控制途径也被激活，但PFN1基因敲除细胞仍会积累受损的、功能失调的线粒体。随后的成像和功能分析表明，PFN1的缺失显著影响线粒体的形态、动力学和呼吸作用。进一步的实验表明，PFN1定位于线粒体基质，可能是从内部调节线粒体功能，而非通过在线粒体表面聚合肌动蛋白来实现。最后，与肌萎缩侧索硬化症（ALS）相关的PFN1突变体无法挽救PFN1基因敲除的线粒体表型，并在线粒体内形成聚集体，进一步扰乱线粒体。总之，这些结果揭示了PFN1在调节线粒体方面的新功能，并确定了与ALS相关的PFN1变体的潜在致病机制。
