Chan W L, Bucher C H, Goldes J, Ma A C, Steiner M, Willie B M, Mundlos S, Kornak U
Institut für Medizinische Genetik Und Humangenetik, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Max-Planck-Institut für Molekulare Genetik, FG Development & Disease, Berlin, Germany.
Aging Cell. 2024 Dec;23(12):e14322. doi: 10.1111/acel.14322. Epub 2024 Sep 5.
GORAB is a key regulator of Golgi vesicle transport and protein glycanation. Loss of GORAB function in gerodermia osteodysplastica (GO) causes shortening of glycosaminoglycan chains, leading to extracellular matrix disorganization that results in wrinkled skin, osteoporosis and elevated TGF-β signaling. In this study, we investigated the role of TGF-β-signaling, oxidative stress, and resulting cellular senescence in the osteoporosis phenotype of GO. Treatment of Gorab conditional knockouts with the TGF-β neutralizing antibody 1D11 rescued the trabecular bone loss, indicating that TGF-β overactivation causes osteoporosis in GO. Using an inducible knockout system, we demonstrated that TGF-β dysregulation was not a cell-intrinsic effect of GORAB inactivation, but a consequence of a disorganized extracellular matrix. Enhanced TGF-β signaling caused elevated Nox4 expression in Gorab mutants and in GO patients' fibroblasts, resulting in overproduction of mitochondrial superoxide. The resulting oxidative stress was detected in GORAB null cells and also in wildtype bystander cells. The same effect was observed in zebrafish after TALEN-mediated gorab inactivation, indicating that the pathway is evolutionarily conserved. Treating Gorab mutants with the antioxidant N-acetylcysteine ameliorated the osteoporosis phenotype. TGF-β induced oxidative stress coincided with accumulation of DNA damage and elevated expression of senescence markers. Inactivation of Cdkn2a in the Gorab rescued the osteoporosis phenotype. Reduced colony formation and altered subpopulations of bone marrow stromal cells were normalized upon inactivation of Cdkn2a, thus further demonstrating the relevance of cellular senescence in the pathogenesis. Our results shed light on the causative role of a TGF-β-Nox4-senescence axis and therapeutic strategies for GO.
GORAB是高尔基体囊泡运输和蛋白质糖基化的关键调节因子。在皮肤骨发育不良（GO）中，GORAB功能丧失会导致糖胺聚糖链缩短，从而导致细胞外基质紊乱，进而引发皮肤皱纹、骨质疏松和转化生长因子-β（TGF-β）信号传导增强。在本研究中，我们调查了TGF-β信号传导、氧化应激以及由此导致的细胞衰老在GO骨质疏松表型中的作用。用TGF-β中和抗体1D11处理Gorab条件性敲除小鼠可挽救小梁骨丢失，这表明TGF-β过度激活会导致GO中的骨质疏松。使用诱导性敲除系统，我们证明TGF-β失调不是GORAB失活的细胞内在效应，而是细胞外基质紊乱的结果。增强的TGF-β信号传导导致Gorab突变体和GO患者成纤维细胞中Nox4表达升高，导致线粒体超氧化物过量产生。在GORAB缺失细胞以及野生型旁观者细胞中均检测到由此产生的氧化应激。在TALEN介导的gorab失活后的斑马鱼中也观察到了相同的效应，这表明该途径在进化上是保守的。用抗氧化剂N-乙酰半胱氨酸处理Gorab突变体可改善骨质疏松表型。TGF-β诱导的氧化应激与DNA损伤积累和衰老标志物表达升高同时发生。在Gorab中使Cdkn2a失活可挽救骨质疏松表型。Cdkn2a失活后，骨髓基质细胞的集落形成减少和亚群改变恢复正常，从而进一步证明细胞衰老在发病机制中的相关性。我们的结果揭示了TGF-β-Nox4-衰老轴的致病作用以及GO的治疗策略。
