Department of Spine Surgery, Department of Orthopedics, School of Medicine, Renji Hospital, Shanghai Jiao Tong University, NO. 160 Pujian Rd, Pudong District, 200127, Shanghai, China.
J Mol Med (Berl). 2023 Feb;101(1-2):171-181. doi: 10.1007/s00109-022-02277-1. Epub 2023 Jan 23.
Inflammation and apoptosis are two important pathological causes of intervertebral disc degeneration (IDD). The crosstalk between these two biological processes during IDD pathogenesis remains elusive. Herein, we discovered that chronic inflammation induced apoptosis through a cullin-RING E3 ligase (CRL)-dependent mechanism. Two cullin proteins, CUL4A and 4B, recruited DNA damage-binding protein 1 (DDB1), RING-box protein 1 (RBX1) and DDB1- and CUL4-associated factor 6 (DCAF6) to assemble a CRL4 E3 ligase in intervertebral discs (IVDs) derived from IDD patients. The CRL4 E3 ligase ubiquitinated and degraded C-terminal-binding protein 1 and 2 (CtBP1/2), two homologues of transcriptional corepressors. The degradation of CtBP1/2 disassociated from the p300-forkhead box O3a (FOXO3a) complex, inducing the expression of B-cell lymphoma 2 (Bcl2)-binding component 3 (BBC3) and causing BBC3-dependent apoptosis. TSC01131, a small molecule that specifically targets CUL4-DDB1 interaction, could inhibit the ubiquitination of CtBP1/2 in vitro and in vivo, thereby decreasing the BBC3 expression level and preventing apoptosis signalling. Using a mouse chronic inflammation model, we found that chronic inflammation could accelerate the IDD process through a conserved CRL4-mediated mechanism. The administration of TSC01131 to mice could significantly improve the outcome of IDD. Collectively, our results revealed that inflammation-dependent CRL4 E3 ligase triggered apoptosis through the removal of CtBP-mediated transrepression. The blockage of the CRL4 E3 ligase by TSC01131 may represent a new therapeutic strategy for IDD treatment. KEY MESSAGES: CUL4A and CUL4B recruited DDB1, RBX1 and DCAF6 to assemble a CRL4 E3 ligase in human IDD biopsies. The CRL4 E3 ligase ubiquitinated and degraded CtBP1/2, causing BBC3-dependent apoptosis. A small molecule TSC01131 that specifically targets CUL4-DDB1 interaction could inhibit the ubiquitination of CtBP1/2, improving the outcome of IDD in a mouse model.
炎症和细胞凋亡是椎间盘退行性变 (IDD) 的两个重要病理原因。这两种生物过程在 IDD 发病机制中的相互作用仍不清楚。在此，我们发现慢性炎症通过一种 Cullin-RING E3 连接酶 (CRL) 依赖性机制诱导细胞凋亡。两种 Cullin 蛋白，CUL4A 和 4B，募集 DNA 损伤结合蛋白 1 (DDB1)、RING 盒蛋白 1 (RBX1) 和 DDB1 和 CUL4 相关因子 6 (DCAF6)，在源自 IDD 患者的椎间盘 (IVD) 中组装 CRL4 E3 连接酶。CRL4 E3 连接酶泛素化和降解 C 端结合蛋白 1 和 2 (CtBP1/2)，CtBP1/2 是转录核心抑制物的两种同源物。CtBP1/2 从 p300-forkhead box O3a (FOXO3a) 复合物中解离，诱导 B 细胞淋巴瘤 2 (Bcl2) 结合成分 3 (BBC3) 的表达，并导致 BBC3 依赖性凋亡。一种专门针对 CUL4-DDB1 相互作用的小分子 TSC01131 可以在体外和体内抑制 CtBP1/2 的泛素化，从而降低 BBC3 的表达水平并阻止凋亡信号。使用慢性炎症的小鼠模型，我们发现慢性炎症可以通过保守的 CRL4 介导的机制加速 IDD 进程。将 TSC01131 施用于小鼠可显著改善 IDD 的结果。总的来说，我们的研究结果揭示了炎症依赖性 CRL4 E3 连接酶通过去除 CtBP 介导的转录阻遏来触发细胞凋亡。通过 TSC01131 阻断 CRL4 E3 连接酶可能代表治疗 IDD 的新治疗策略。关键信息：CUL4A 和 CUL4B 在人类 IDD 活检中募集 DDB1、RBX1 和 DCAF6 组装 CRL4 E3 连接酶。CRL4 E3 连接酶泛素化和降解 CtBP1/2，导致 BBC3 依赖性凋亡。一种专门针对 CUL4-DDB1 相互作用的小分子 TSC01131 可以抑制 CtBP1/2 的泛素化，改善小鼠模型中 IDD 的结果。
