Montes Iris D, Amirthagunanathan Suganthan, Joshi Amit S, Raman Malavika
Department of Developmental Molecular and Chemical Biology, Tufts University School of Medicine, Boston MA.
Department of Biochemistry & Cell and Molecular Biology, University of Tennessee, Knoxville, TN.
bioRxiv. 2024 Sep 26:2024.09.24.614749. doi: 10.1101/2024.09.24.614749.
Peroxisomes are vital organelles involved in key metabolic functions in eukaryotic cells. Their significance is highlighted by peroxisome biogenesis disorders; severe childhood diseases marked by disrupted lipid metabolism. One mechanism regulating peroxisome abundance is through selective ubiquitylation of peroxisomal membrane proteins that triggers peroxisome degradation via selective autophagy (pexophagy). However, the mechanisms regulating pexophagy remain poorly understood in mammalian cells. Here we show that the evolutionarily conserved AAA-ATPase p97 and its membrane embedded adaptor UBXD8 are essential for maintaining peroxisome abundance. From quantitative proteomic studies we reveal that loss of UBXD8 affects many peroxisomal proteins. We find depletion of UBXD8 results in a loss of peroxisomes in a manner that is independent of the known role of UBXD8 in ER associated degradation (ERAD). Loss of UBXD8 or inhibition of p97 increases peroxisomal turnover through autophagy and can be rescued by depleting key autophagy proteins or overexpressing the deubiquitylating enzyme USP30. Furthermore, we find increased ubiquitylation of the peroxisomal membrane protein PMP70 in cells lacking UBXD8 or p97. Collectively, our findings identify a new role for the p97-UBXD8 complex in regulating peroxisome abundance by suppressing pexophagy.
过氧化物酶体是真核细胞中参与关键代谢功能的重要细胞器。过氧化物酶体生物发生障碍突出了它们的重要性，这是一类以脂质代谢紊乱为特征的严重儿童疾病。一种调节过氧化物酶体丰度的机制是通过过氧化物酶体膜蛋白的选择性泛素化，从而触发通过选择性自噬（过氧化物酶体自噬）进行的过氧化物酶体降解。然而，在哺乳动物细胞中，调节过氧化物酶体自噬的机制仍知之甚少。在这里，我们表明进化上保守的AAA-ATP酶p97及其膜嵌入适配器UBXD8对于维持过氧化物酶体丰度至关重要。通过定量蛋白质组学研究，我们发现UBXD8的缺失会影响许多过氧化物酶体蛋白。我们发现UBXD8的耗竭导致过氧化物酶体的丧失，其方式独立于UBXD8在内质网相关降解（ERAD）中的已知作用。UBXD8的缺失或p97的抑制通过自噬增加过氧化物酶体的周转，并且可以通过耗尽关键自噬蛋白或过表达去泛素化酶USP30来挽救。此外，我们发现在缺乏UBXD8或p97的细胞中，过氧化物酶体膜蛋白PMP70的泛素化增加。总的来说，我们的研究结果确定了p97-UBXD8复合物在通过抑制过氧化物酶体自噬来调节过氧化物酶体丰度方面的新作用。
