Park Na Yeon, Jo Doo Sin, Yang Jae-Yoon, Bae Ji-Eun, Kim Joon Bum, Kim Yong Hwan, Kim Seong Hyun, Kim Pansoo, Lee Dong-Seok, Yoshimori Tamotsu, Jo Eun-Kyeong, Yeom Eunbyul, Cho Dong-Hyung
School of Life Sciences, BK21 FOUR KNU Creative BioRearch Group, Kyungpook National University, Daegu, South Korea.
Organelle Institute, Kyungpook National University, Daegu, South Korea.
Nat Commun. 2025 Jan 28;16(1):1109. doi: 10.1038/s41467-025-56294-y.
Lysophagy eliminates damaged lysosomes and is crucial to cellular homeostasis; however, its underlying mechanisms are not entirely understood. We screen a ubiquitination-related compound library and determine that the substrate recognition component of the SCF-type E3 ubiquitin ligase complex, SCF(FBXO3), which is a critical lysophagy regulator. Inhibition of FBXO3 reduces lysophagy and lysophagic flux in response to L-leucyl-L-leucine methyl ester (LLOMe). Furthermore, FBXO3 interacts with TMEM192, leading to its ubiquitination in LLOMe-treated cells. We also identify TAX1BP1 as a critical autophagic adaptor that recognizes ubiquitinated TMEM192 during lysophagy and find that TBK1 activation is crucial for lysophagy, as it phosphorylates FBXO3 in response to lysosomal damage. Knockout of FBXO3 significantly impairs lysophagy, and its reconstitution with a loss-of-function mutant (V221I) further confirms its essential role in lysophagy regulation. Collectively, our findings highlight the significance of the TBK1-FBXO3-TMEM192-TAX1BP1 axis in lysophagy and emphasize the critical role of FBXO3 in lysosomal integrity.
溶酶体自噬可清除受损的溶酶体，对细胞内稳态至关重要；然而，其潜在机制尚未完全明确。我们筛选了一个泛素化相关化合物库，并确定SCF型E3泛素连接酶复合物的底物识别成分SCF(FBXO3)是一种关键的溶酶体自噬调节因子。抑制FBXO3会降低对L-亮氨酰-L-亮氨酸甲酯（LLOMe）的溶酶体自噬及溶酶体自噬通量。此外，FBXO3与TMEM192相互作用，导致其在经LLOMe处理的细胞中发生泛素化。我们还确定TAX1BP1是一种关键的自噬衔接蛋白，在溶酶体自噬过程中识别泛素化的TMEM192，并发现TBK1激活对溶酶体自噬至关重要，因为它在溶酶体损伤时使FBXO3磷酸化。敲除FBXO3会显著损害溶酶体自噬，用功能缺失突变体（V221I）对其进行重建进一步证实了其在溶酶体自噬调节中的重要作用。总的来说，我们的研究结果突出了TBK1-FBXO3-TMEM192-TAX1BP1轴在溶酶体自噬中的重要性，并强调了FBXO3在溶酶体完整性中的关键作用。
