Alternative NF-κB Regulates RANKL-Induced Osteoclast Differentiation and Mitochondrial Biogenesis via Independent Mechanisms.
Alternative NF-κB Regulates RANKL-Induced Osteoclast Differentiation and Mitochondrial Biogenesis via Independent Mechanisms.
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DOI：
10.1002/jbmr.2584
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发表时间：
2015-12
期刊：
影响因子：
--
通讯作者：
Novack DV
中科院分区：
文献类型：
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作者：
Zeng R;Faccio R;Novack DV
线粒体生物发生，即新的线粒体DNA和蛋白质的产生，与破骨细胞（OC）的分化和功能有关。在这项研究中，我们使用了在关键的替代NF-κB途径蛋白RelB和NIK中突变的小鼠，以剖析线粒体生物发生和破骨细胞发生之间的复杂关系。OC前体缺乏NIK或RelB，RANKL不能增加线粒体DNA或OxPhos蛋白表达，与较低的耗氧率相关。与对照组相比，表达组成型活性NIK的转基因OC前体显示出正常的RANKL诱导的线粒体生物合成（OxPhos表达和线粒体拷贝数），但线粒体尺寸更大，耗氧速率增加，表明线粒体功能增加。为了推断NIK和RelB缺陷前体中线粒体生物合成缺陷的机制，我们检测了已知控制这一过程的基因的表达。在RelB−/−和NIK−/− OC中，PGC-1β（Ppargc 1b）表达显著降低，但PGC-1α、PPRC 1或ERRα表达不显著降低。由于PGC-1β已被报道可积极调节OC中的线粒体生物发生和分化，我们在RelB−/−细胞中逆转录病毒过表达PGC-1β，但令人惊讶的是，它不影响分化，也不恢复RANKL诱导的线粒体生物发生。为了确定RelB缺陷细胞中破骨细胞生成的阻断是否排除了线粒体生物发生，我们通过NFATc 1的过表达拯救了RelB−/−分化。WT和RelB缺陷培养物中的线粒体参数均未受到NFATc 1过表达的影响，RelB −/−中的骨吸收未恢复。此外，NFATc 1与PGC-1β的共过表达虽然允许OC分化，但通过CTX-I水平，并不能拯救RelB−/− OC中的线粒体生物发生或骨吸收。因此，我们的研究结果表明，替代NF-κB途径在控制OC分化和OC线粒体生物合成的独立过程中发挥双重但不同的作用。此外，PGC-1β不能在没有RelB的OC中驱动线粒体生物发生，表明线粒体调节中的细胞类型特异性。
Mitochondrial biogenesis, the generation of new mitochondrial DNA and proteins, has been linked to osteoclast (OC) differentiation and function. In this study we used mice with mutations in key alternative NF-κB pathway proteins, RelB and NIK, to dissect the complex relationship between mitochondrial biogenesis and osteoclastogenesis. OC precursors lacking either NIK or RelB, RANKL were unable to increase mitochondrial DNA or OxPhos protein expression, associated with lower oxygen consumption rates. Transgenic OC precursors expressing constitutively active NIK showed normal RANKL-induced mitochondrial biogenesis (OxPhos expression and mitochondria copy number) compared to controls, but larger mitochondrial dimensions and increased oxygen consumption rates, suggesting increased mitochondrial function. To deduce the mechanism for mitochondrial biogenesis defects in NIK- and RelB-deficient precursors, we examined expression of genes known to control this process. PGC-1β (Ppargc1b) expression, but not PGC-1α, PPRC1 or ERRα, was significantly reduced in RelB−/− and NIK−/− OCs. Because PGC-1β has been reported to positively regulate both mitochondrial biogenesis and differentiation in OCs, we retrovirally overexpressed PGC-1β in RelB−/− cells, but surprisingly found that it did not affect differentiation, nor restore RANKL-induced mitochondrial biogenesis. To determine whether the blockade in osteoclastogenesis in RelB-deficient cells precludes mitochondrial biogenesis, we rescued RelB−/− differentiation via overexpression of NFATc1. Mitochondrial parameters in neither WT nor RelB-deficient cultures were affected by NFATc1 overexpression, and bone resorption in RelB −/− was not restored. Furthermore, NFATc1 co-overexpression with PGC-1β, while allowing OC differentiation, did not rescue mitochondrial biogenesis or bone resorption in RelB−/− OCs, by CTX-I levels. Thus, our results indicate that the alternative NF-κB pathway plays dual, but distinct roles in controlling the independent processes of OC differentiation and OC mitochondrial biogenesis. Furthermore, the inability of PGC-1β to drive mitochondrial biogenesis in OCs without RelB indicates a cell-type specificity in mitochondria regulation.