Leukemia/lymphoma-related factor (LRF) or osteoclast zinc finger protein (OCZF) overexpression promotes osteoclast survival by increasing Bcl-xl mRNA: A novel regulatory mechanism mediated by the RNA binding protein SAM68
Leukemia/lymphoma-related factor (LRF) or osteoclast zinc finger protein (OCZF) overexpression promotes osteoclast survival by increasing Bcl-xl mRNA: A novel regulatory mechanism mediated by the RNA binding protein SAM68
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DOI：
10.1038/s41374-022-00792-w
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发表时间：
2022-04
影响因子：
5
通讯作者：
Xianghe Xu;T. Shobuike;M. Shiraki;Asana Kamohara;Hirohito Hirata;Masatoshi Murayama;Daisuke Mawatari;Masaya Ueno;T. Morimoto;T. Kukita;M. Mawatari;A. Kukita
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文献类型：
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作者：
Xianghe Xu;T. Shobuike;M. Shiraki;Asana Kamohara;Hirohito Hirata;Masatoshi Murayama;Daisuke Mawatari;Masaya Ueno;T. Morimoto;T. Kukita;M. Mawatari;A. Kukita
RANKL诱导NFATc1，NFATc1是诱导破骨细胞特异性基因如组织蛋白K的关键转录因子，而对破骨细胞存活的转录控制尚不完全清楚。小鼠白血病/淋巴瘤相关因子(LRF)和大鼠破骨细胞锌指蛋白(OCZF)是锌指和含BTB结构域蛋白(ZBTB)家族的转录调控因子，是重要的造血调控因子。我们之前已经证明，OCZF转基因(TG)小鼠的破骨细胞的分化和存活率得到了提高。在本研究中，我们揭示了LRF/OCZF调节破骨细胞存活的可能机制，以及OCZF过表达在病理性骨丢失中的作用。在体外培养中，LRF与NFATc1在破骨细胞形成早期高度共存，但在分化为成熟破骨细胞后仅有LRF表达。在牙本质切片上形成的吸收破骨细胞中，LRF的表达进一步增强。破骨细胞存活抑制剂，如阿伦磷酸钠，一种双膦酸盐，减少了LRF的表达。显微CT评估显示，OCZF-TG小鼠的股骨体积明显小于WT小鼠。此外，OCZF的过表达显著促进了去卵巢诱导的溶骨性小鼠模型的骨丢失。在OCZF-TG小鼠破骨细胞形成的培养中，通过选择性剪接形成的抗凋亡的Bcl-xlmRNA的表达增强。相反，在OCZF-TG小鼠来源的培养中，促凋亡的Bcl-xsmRNA的表达缺失。我们发现，在OCZFTG小鼠来源的破骨细胞中，与有丝分裂相关的68 kDa(Sam68)蛋白的RNA结合剪接调节因子、src底物的表达水平显著降低。此外，shRNA介导的下调Sam68基因表达增加了Bclx1mRNA的表达，提示SAM68调控Bclxl基因的表达。这些结果表明，OCZF过表达降低了Sam68的蛋白水平，从而促进了破骨细胞的存活，提示LRF/OCZF是一个有希望的调控病理性骨丢失的靶点。
RANKL induces NFATc1, a key transcriptional factor to induce osteoclast-specific genes such as cathepsin K, whereas transcriptional control of osteoclast survival is not fully understood. Leukemia/lymphoma-related factor (LRF) in mouse and osteoclast zinc finger protein (OCZF) in rat are zinc finger and BTB domain-containing protein (zBTB) family of transcriptional regulators, and are critical regulators of hematopoiesis. We have previously shown that differentiation and survival were enhanced in osteoclasts from OCZF-Transgenic (Tg) mice. In the present study, we show a possible mechanism of osteoclast survival regulated by LRF/OCZF and the role of OCZF overexpression in pathological bone loss. In the in vitro cultures, LRF was highly colocalized with NFATc1 in cells of early stage in osteoclastogenesis, but only LRF expression persisted after differentiation into mature osteoclasts. LRF expression was further enhanced in resorbing osteoclasts formed on dentin slices. Osteoclast survival inhibitor such as alendronate, a bisphosphonate reduced LRF expression. Micro CT evaluation revealed that femurs of OCZF-Tg mice showed significantly lower bone volume compared to that of WT mice. Furthermore, OCZF overexpression markedly promoted bone loss in ovariectomy-induced osteolytic mouse model. The expression of anti-apoptoticBcl-xlmRNA, which is formed by alternative splicing, was enhanced in the cultures in which osteoclasts are formed from OCZF-Tg mice. In contrast, the expression of pro-apoptoticBcl-xsmRNA was lost in the culture derived from OCZF-Tg mice. We found that the expression levels of RNA binding splicing regulator, Src substrate associated in mitosis of 68 kDa (Sam68) protein were markedly decreased in OCZF-Tg mice-derived osteoclasts. In addition, shRNA-mediated knockdown of Sam68 expression increased the expression ofBcl-xlmRNA, suggesting that SAM68 regulates the expression ofBcl-xl. These results indicate that OCZF overexpression reduces protein levels of Sam68, thereby promotes osteoclast survival, and suggest that LRF/OCZF is a promising target for regulating pathological bone loss.