Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA; Division of Digestive Diseases, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA.
CSIR-Institute of Genomics and Integrative Biology, New Delhi, India; Academy of Scientific and Innovative Research, Ghaziabad, India.
Mol Cell. 2024 Nov 21;84(22):4436-4453.e8. doi: 10.1016/j.molcel.2024.10.022. Epub 2024 Nov 8.
Lipophagy is a ubiquitous mechanism for degradation of lipid droplets (LDs) in lysosomes. Autophagy receptors selectively target organelles for lysosomal degradation. The selective receptor for lipophagy remains elusive. Using mouse liver phosphoproteomics and human liver transcriptomics, we identify vacuolar-protein-sorting-associated protein 4A (VPS4A), a member of a large family AAA+ ATPases, as a selective receptor for lipophagy. We show that phosphorylation of VPS4A on Ser and its localization to LDs in response to fasting drives lipophagy. Imaging/three-dimensional (3D) reconstruction and biochemical analyses reveal the concomitant degradation of VPS4A and LDs in lysosomes in an autophagy-gene-7-sensitive manner. Either silencing VPS4A or targeting VPS4A phosphorylation or VPS4A binding to LDs or LC3 blocks lipophagy without affecting other forms of selective autophagy. Finally, VPS4A levels and markers of lipophagy are markedly reduced in human steatotic livers-revealing a fundamental role of VPS4A as the lipophagy receptor in mice and humans.
脂噬作用是溶酶体降解脂质滴(LDs)的一种普遍机制。自噬受体选择性地将细胞器靶向溶酶体降解。脂噬作用的选择性受体仍然难以捉摸。使用小鼠肝磷酸蛋白质组学和人肝转录组学,我们确定液泡蛋白分选相关蛋白 4A(VPS4A),一种大型 AAA+ATP 酶家族的成员,是脂噬作用的选择性受体。我们表明,VPS4A 在丝氨酸上的磷酸化及其在饥饿反应中向 LDs 的定位驱动脂噬作用。成像/三维(3D)重建和生化分析揭示了 VPS4A 和 LDs 在溶酶体中以自噬基因 7 敏感的方式同时降解。沉默 VPS4A 或靶向 VPS4A 磷酸化或 VPS4A 与 LDs 或 LC3 的结合均可阻断脂噬作用,而不影响其他形式的选择性自噬。最后,VPS4A 水平和脂噬作用的标志物在人脂肪性肝中显著降低——揭示了 VPS4A 作为小鼠和人类脂噬作用受体的基本作用。