Department of Orthopedic Surgery and Biological Engineering and Regenerative Medicine Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
J Bone Miner Res. 2021 Oct;36(10):2065-2080. doi: 10.1002/jbmr.4399. Epub 2021 Jul 26.
ATP-citrate lyase (ACLY), generating most of the nucleocytosolic acetyl coenzyme A (acetyl-CoA) for histone acetylation, links cell metabolism to epigenetic regulation. Recent investigations demonstrated that ACLY activated by metabolic reprogramming played an essential role in both M1 and M2 macrophage activation via histone acetylation. Previous studies also revealed that histone methylation and acetylation were critical for transcriptional regulation of osteoclast-specific genes. Considering that osteoclast differentiation also undergoes metabolic reprogramming and the activity of ACLY is always Akt-dependent, we inferred that receptor activator of NF-κB (RANK) activation might enhance the activity of ACLY through downstream pathways and ACLY might play a role in osteoclast formation. In the current study, we found that ACLY was gradually activated during RANK ligand (RANKL)-induced osteoclast differentiation from bone marrow-derived macrophages (BMMs). Both ACLY knock-down and small molecular ACLY inhibitor BMS-303141 significantly decreased nucleocytosolic acetyl-CoA in BMMs and osteoclasts and suppressed osteoclast formation in vitro. BMS-303141 also suppressed osteoclast formation in vivo and prevents ovariectomy (OVX)-induced bone loss. Further investigations showed that RANKL triggered ACLY translocation into nucleus, consistent with increasing histone H3 acetylation, which was correlated to ACLY. The H3 lysine residues influenced by ACLY were in accordance with GCN5 targets. Using GCN5 knock-down and overexpression, we showed that ACLY and GCN5 functioned in the same pathway for histone H3 acetylation. Analysis of pathways downstream of RANK activation revealed that ACLY was Akt-dependent and predominately affected Akt pathway. With the help of RNA-sequencing, we discovered Rac1 as a downstream regulator of ACLY, which was involved in shACLY-mediated suppression of osteoclast differentiation, cytoskeleton organization, and signal transduction and was transcriptionally regulated by ACLY via histone H3 acetylation. To summarize, our results proved that inhibition of ATP-citrate lyase led to suppression of osteoclast differentiation and function via regulation of histone acetylation. Rac1 could be a downstream regulator of ACLY. © 2021 American Society for Bone and Mineral Research (ASBMR).
三磷酸腺苷-柠檬酸裂解酶（ACLY）生成大多数核细胞质乙酰辅酶 A（乙酰-CoA）用于组蛋白乙酰化，将细胞代谢与表观遗传调控联系起来。最近的研究表明，代谢重编程激活的 ACLY 通过组蛋白乙酰化在 M1 和 M2 巨噬细胞激活中发挥重要作用。先前的研究还表明，组蛋白甲基化和乙酰化对于破骨细胞特异性基因的转录调控至关重要。考虑到破骨细胞分化也经历代谢重编程，并且 ACLY 的活性始终依赖 Akt，我们推断核因子-κB 受体激活物（RANK）的激活可能通过下游途径增强 ACLY 的活性，并且 ACLY 可能在破骨细胞形成中发挥作用。在本研究中，我们发现 RANK 配体（RANKL）诱导骨髓来源巨噬细胞（BMM）中的破骨细胞分化过程中，ACLY 逐渐被激活。ACLY 敲低和小分子 ACLY 抑制剂 BMS-303141 均显著降低了 BMM 和破骨细胞中的核细胞质乙酰-CoA，并抑制了体外破骨细胞的形成。BMS-303141 还抑制了体内破骨细胞的形成并预防了卵巢切除（OVX）诱导的骨丢失。进一步的研究表明，RANKL 触发 ACLY 向核内易位，与组蛋白 H3 乙酰化增加一致，这与 ACLY 相关。受 ACLY 影响的 H3 赖氨酸残基与 GCN5 的靶标一致。通过 GCN5 敲低和过表达，我们表明 ACLY 和 GCN5 在组蛋白 H3 乙酰化的同一途径中起作用。对 RANK 激活下游途径的分析表明，ACLY 依赖 Akt，主要影响 Akt 途径。在 RNA 测序的帮助下，我们发现 Rac1 是 ACLY 的下游调节因子，它参与了 shACLY 介导的破骨细胞分化、细胞骨架组织和信号转导的抑制，并且通过组蛋白 H3 乙酰化转录调控。总之，我们的结果证明，抑制三磷酸腺苷-柠檬酸裂解酶通过调节组蛋白乙酰化导致破骨细胞分化和功能的抑制。Rac1 可能是 ACLY 的下游调节因子。2021 年美国骨骼与矿物质研究协会（ASBMR）。
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