PO.MCB09.04 · 分子与细胞生物学
重塑谷氨酰胺代谢可恢复多发性骨髓瘤中的成骨细胞分化
Rewiring glutamine metabolism restores osteoblast differentiation in multiple myeloma
作者与单位 Authors & Affiliations
摘要 Abstract
中文摘要
超过80%的多发性骨髓瘤(MM)患者在诊断时即伴有病理性骨折或骨溶解。目前尚无聚焦于恢复MM溶骨性病变患者中造骨成骨细胞的治疗策略。MM中的代谢重塑表现为对谷氨酰胺的高度依赖或“成瘾”，导致局部微环境(即骨骼)中谷氨酰胺耗竭。值得注意的是，谷氨酰胺对于驱动向造骨成骨细胞的定向和分化以满足高合成代谢需求至关重要。谷氨酰胺依赖性成骨细胞祖细胞如何感知并响应MM引起的谷氨酰胺耗竭，其机制尚未探明。在本研究中，我们证明关键成骨细胞分化转录因子——Runt相关转录因子2(RUNX2)的多聚谷氨酰胺链，作为分子传感器对谷氨酰胺耗竭极其敏感，从而在MM形成的谷氨酰胺缺乏的骨微环境中抑制成骨细胞分化。我们使用生长实验、基因表达分析及分化染色实验评估成骨细胞分化。使用基于荧光报告基因的实验和膜上实验测量新生mRNA翻译。这些系统在谷氨酰胺耗竭、重定向或与MM细胞共培养的条件下进行分析。我们的发现表明，多聚谷氨酰胺链感知由谷氨酰胺tRNA去负载所致的谷氨酰胺不足，导致新生RUNX2 mRNA翻译受抑制，进而抑制成骨细胞分化。缺失或缩短多聚谷氨酰胺链使RUNX2对谷氨酰胺耗竭不敏感。在谷氨酰胺耗竭的成骨细胞祖细胞中超生理水平的RUNX2会损害细胞适应度，提示这一感知机制具有适应性功能。此外，在成骨细胞祖细胞中，将谷氨酰胺重定向至合成代谢通路可在谷氨酰胺耗竭下恢复新生RUNX2翻译和成骨细胞分化。我们发现MM细胞抑制成骨细胞分化，而这可通过在成骨细胞祖细胞中重定向谷氨酰胺来恢复。这些发现表明，关键转录因子RUNX2拥有一个内置的谷氨酰胺传感器——多聚谷氨酰胺链，使其能够适应谷氨酰胺缺乏并据此作出细胞命运决定。在成骨细胞祖细胞中重定向谷氨酰胺以使谷氨酰胺可用于分化，代表了一种恢复MM骨微环境中骨形成的新型治疗策略。
查看英文原文 English abstract
More than 80% of multiple myeloma (MM) patients are diagnosed with pathological bone fractures or osteolysis. Currently, no therapeutic strategies focus on restoring bone-building osteoblast cells in patients with MM osteolytic lesions. Metabolic rewiring in MM displays high glutamine dependence or “addiction”, leading to glutamine depletion from the local niche, the bone. Notably, glutamine is essential for driving commitment and differentiation into bone-building osteoblasts to meet the high anabolic demands. The mechanism by which the glutamine-dependent osteoblast progenitor cells sense and respond to glutamine depletion by MM is unexplored. In this study, we demonstrate that the polyglutamine tract of the key osteoblast-differentiation transcription factor, Runt-related transcription factor 2 (RUNX2), serves as the molecular sensor that is exquisitely sensitive to glutamine depletion and consequently inhibits osteoblast differentiation in a glutamine-deprived bone niche developed by MM. We assessed osteoblast differentiation using growth assay, gene expression analysis, and differentiation staining assays. Nascent mRNA translation was measured using a fluorescent reporter-based assay and an on-membrane assay. These systems were analyzed under glutamine depletion, rerouting, or with MM cells. Our findings demonstrate that the polyglutamine tract senses a glutamine deficit resulting from the uncharging of glutamine tRNAs, leading to the suppression of translation of nascent RUNX2 mRNA and, consequently, osteoblast differentiation. Deletion or shortening of the polyglutamine tract renders RUNX2 insensitive to glutamine depletion. Supraphysiological RUNX2 in glutamine-depleted osteoblast progenitors compromises cell fitness, suggesting an adaptive function for this sensing mechanism. Furthermore, in osteoblast progenitors, rerouting glutamine towards anabolic pathways restores nascent RUNX2 translation and osteoblast differentiation under glutamine depletion. We found that MM cells suppress osteoblast differentiation, which can be restored by rerouting glutamine in osteoblast progenitors. These findings demonstrate that the critical transcription factor RUNX2 possesses an in-built glutamine sensor, the polyglutamine tract, which enables it to adapt and make cell fate decisions in response to glutamine deficit. Rerouting glutamine in osteoblast progenitors to make glutamine available for differentiation represents a novel therapeutic strategy to restore bone formation in the MM bone niche.
利益披露 Disclosure
M. Shirin, None..
N. N. Pavlova, None.