Phase separation of Nur77 mediates celastrol-induced mitophagy by promoting the liquidity of p62/SQSTM1 condensates

• Published in: Nature communications Vol. 12; no. 1; p. 5989
• Main Authors: Peng, Shuang-zhou, Chen, Xiao-hui, Chen, Si-jie, Zhang, Jie, Wang, Chuan-ying, Liu, Wei-rong, Zhang, Duo, Su, Ying, Zhang, Xiao-kun
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13.10.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 13/31; 14/10; 14/19; 14/35; 38; 631/80/39/2348; 631/80/86/388; Animals; Autophagy; Condensates; Domains; Electron Transport Complex IV; Female; Gene Expression Regulation; Genes, Reporter; Green Fluorescent Proteins; HeLa Cells; Humanities and Social Sciences; Humans; Liquid phases; Liquidity; Luminescent Proteins; Mice; Mice, Inbred C57BL; Mitochondria; Mitochondria - drug effects; Mitochondria - genetics; Mitochondria - metabolism; Mitophagy; Mitophagy - drug effects; Mitophagy - genetics; multidisciplinary; Nuclear Receptor Subfamily 4, Group A, Member 1 - genetics; Nuclear Receptor Subfamily 4, Group A, Member 1 - metabolism; Nur77 protein; Pentacyclic Triterpenes - pharmacology; Phagocytosis; Phase separation; Protein Binding; Protein folding; Protein Transport; Recombinant Fusion Proteins; Red Fluorescent Protein; Rheology; Science; Science (multidisciplinary); Sequestering; Sequestosome-1 Protein - genetics; Sequestosome-1 Protein - metabolism; Tethering; Tumor Necrosis Factor-alpha - pharmacology
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-26295-8

Liquid-liquid phase separation promotes the formation of membraneless condensates that mediate diverse cellular functions, including autophagy of misfolded proteins. However, how phase separation participates in autophagy of dysfunctional mitochondria (mitophagy) remains obscure. We previously discovered that nuclear receptor Nur77 (also called TR3, NGFI-B, or NR4A1) translocates from the nucleus to mitochondria to mediate celastrol-induced mitophagy through interaction with p62/SQSTM1. Here, we show that the ubiquitinated mitochondrial Nur77 forms membraneless condensates capable of sequestrating damaged mitochondria by interacting with the UBA domain of p62/SQSTM1. However, tethering clustered mitochondria to the autophagy machinery requires an additional interaction mediated by the N-terminal intrinsically disordered region (IDR) of Nur77 and the N-terminal PB1 domain of p62/SQSTM1, which confers Nur77-p62/SQSTM1 condensates with the magnitude and liquidity. Our results demonstrate how composite multivalent interaction between Nur77 and p62/SQSTM1 coordinates to sequester damaged mitochondria and to connect targeted cargo mitochondria for autophagy, providing mechanistic insight into mitophagy. How phase separation participates in mitophagy remains unclear. Here the authors show that Nur77 and p62/SQSTM1 through “head-to-head” and “tail-to-tail” interactions form membraneless condensates capable of sequestering dysfunctional mitochondria and tethering them to autolysosome for degradation.