Rab11A Functions as a Negative Regulator of Osteoclastogenesis through Dictating Lysosome-Induced Proteolysis of c-fms and RANK Surface Receptors.
Rab11A Functions as a Negative Regulator of Osteoclastogenesis through Dictating Lysosome-Induced Proteolysis of c-fms and RANK Surface Receptors.
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DOI：
10.3390/cells9112384
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发表时间：
2020-10-31
期刊：
影响因子：
6
通讯作者：
Okamoto K
中科院分区：
文献类型：
--
作者：
Okusha Y;Tran MT;Itagaki M;Sogawa C;Eguchi T;Okui T;Kadowaki T;Sakai E;Tsukuba T;Okamoto K
破骨细胞的分化和活性受两种基本细胞因子巨噬细胞集落刺激因子（M-CSF）和核因子-κB配体受体激活因子（RANKL）的控制。Rab 11 A GTP酶是Ras超家族中最大的分支，属于Rab 11亚家族，是细胞表面受体循环的重要调节因子。然而，Rab 11 A在破骨细胞分化中的调节作用还完全未知。在这项研究中，我们发现Rab 11 A在来自骨髓源性巨噬细胞（BBM）或RAW-D小鼠破骨细胞前体细胞的破骨细胞分化的晚期阶段强烈上调。Rab 11 A沉默促进破骨细胞形成，并显著增加c-fms和核因子-κB受体激活剂（RANK）的表面水平，而其过表达则减弱破骨细胞形成以及c-fms和RANK的表面水平。利用免疫细胞化学染色追踪Rab 11 A囊泡定位，我们观察到Rab 11 A定位于早期和晚期内体，但不是溶酶体。有趣的是，Rab 11 A过表达导致荧光强度增强和早期内体的基于尺寸的扩大。此外，Rab 11 A过表达通过升高破骨细胞中特定溶酶体蛋白LAMP 1和两种关键溶酶体酶组织蛋白酶B和D的内源性水平来促进溶酶体活性。更重要的是，通过氯喹抑制溶酶体活性，我们发现破骨细胞中c-fms和RANK蛋白的内源性水平增强。根据这些观察结果，我们提出Rab 11 A作为破骨细胞生成负调节剂的新功能，主要通过（i）消除c-fms和RANK受体的表面丰度，和（ii）上调溶酶体活性，随后增加c-fms和RANK受体的降解，可能通过破骨细胞中的早期内体-晚期内体-溶酶体轴。
Osteoclast differentiation and activity are controlled by two essential cytokines, macrophage colony-stimulating factor (M-CSF) and the receptor activator of nuclear factor-κB ligand (RANKL). Rab11A GTPase, belonging to Rab11 subfamily representing the largest branch of Ras superfamily of small GTPases, has been identified as one of the crucial regulators of cell surface receptor recycling. Nevertheless, the regulatory role of Rab11A in osteoclast differentiation has been completely unknown. In this study, we found that Rab11A was strongly upregulated at a late stage of osteoclast differentiation derived from bone marrow-derived macrophages (BMMs) or RAW-D murine osteoclast precursor cells. Rab11A silencing promoted osteoclast formation and significantly increased the surface levels of c-fms and receptor activator of nuclear factor-κB (RANK) while its overexpression attenuated osteoclast formation and the surface levels of c-fms and RANK. Using immunocytochemical staining for tracking Rab11A vesicular localization, we observed that Rab11A was localized in early and late endosomes, but not lysosomes. Intriguingly, Rab11A overexpression caused the enhancement of fluorescent intensity and size-based enlargement of early endosomes. Besides, Rab11A overexpression promoted lysosomal activity via elevating the endogenous levels of a specific lysosomal protein, LAMP1, and two key lysosomal enzymes, cathepsins B and D in osteoclasts. More importantly, inhibition of the lysosomal activity by chloroquine, we found that the endogenous levels of c-fms and RANK proteins were enhanced in osteoclasts. From these observations, we suggest a novel function of Rab11A as a negative regulator of osteoclastogenesis mainly through (i) abolishing the surface abundance of c-fms and RANK receptors, and (ii) upregulating lysosomal activity, subsequently augmenting the degradation of c-fms and RANK receptors, probably via the axis of early endosomes–late endosomes–lysosomes in osteoclasts.
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影响因子：
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作者：
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通讯作者：
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