Fyn positively regulates the activation of DAP12 and FcRγ-mediated costimulatory signals by RANKL during osteoclastogenesis
Fyn positively regulates the activation of DAP12 and FcRγ-mediated costimulatory signals by RANKL during osteoclastogenesis
复制标题
DOI：
10.1016/j.cellsig.2012.02.014
复制
发表时间：
2012-06-01
影响因子：
4.8
通讯作者：
Choi, W. S.
中科院分区：
文献类型：
--
作者：
Kim, H. S.;Kim, D. K.;Choi, W. S.
破骨细胞是唯一的骨吸收细胞，与骨质疏松症和类风湿性关节炎等多种骨相关疾病密切相关。从骨髓巨噬细胞(BMMS)向OCs的分化受RANK和适配器蛋白(DAP12/FCR-γ)介导的共刺激信号的调节。然而，RANKL/RANK信号如何刺激DAP12/FCRγ的磷酸化从而启动共刺激信号尚不清楚。我们发现，在RANKL刺激的Fyn(-/-)或Fyn-siRNA转基因的BMMS中，OC的分化和骨吸收能力的获得受到抑制，但在Fyn(-/-)BMMS中过表达Fyn激酶可以恢复OC的分化和骨吸收能力的获得。然而，Fyn的缺失并不影响RANKL刺激的骨髓基质细胞的增殖。此外，RANKL刺激的Fyn(-/-)BMMS不再表现出对典型OC标志物(如NFATc1、c-Fos、c-Src、TRAF6和组织蛋白K)的最佳诱导或共刺激信号(如Syk、PLC Gamma 2和Gab2的激活磷酸化)。通过Fyn(-/-)BMMS中Fyn的过度表达，这些改变得以恢复。免疫沉淀研究还表明，在RANKL刺激BMMS过程中，适配蛋白DAP12/FCR-γ和Syk与RANK发生了一定程度的相互作用。在Fyn(-/-)BMMS中，DAP12/FCRγ的磷酸化和Syk的募集被抑制。这是第一次演示FYN将初始RANK/RANKL信号转发到包含ITAM的适配器DAP12/FCR伽马以进行OC区分。(C)2012 Elsevier Inc.保留所有权利。
Osteoclasts (OCs) are the only bone-resorbing cells and are critically involved in various bone-associated diseases, including osteoporosis and rheumatoid arthritis. Differentiation of OCs from bone marrow macrophage cells (BMMs) is regulated by RANK and the adaptor protein (DAP12/FcR gamma)-mediated costimulatory signals. However, it is unknown how RANKL/RANK signal stimulates phosphorylation of DAP12/FcR gamma to initiate the costimulatory signals. As reported here, we found that OC differentiation and acquisition of bone resorption capacity were suppressed in RANKL-stimulated Fyn(-/-) or Fyn-siRNA-transfected BMMs, but could be restored by overexpression of Fyn kinase in Fyn(-/-) BMMs. However, the RANKL-stimulated proliferation of BMMs was unaffected by the absence of Fyn. In addition, RANKL-stimulated Fyn(-/-) BMMs no longer exhibited the optimal induction of typical OC markers such as NFATc1, c-Fos, c-Src, TRAF6, and cathepsin K or costimulatory signals such as the activating phosphorylations of Syk, PLC gamma 2, and Gab2. These were restored by overexpression of Fyn in Fyn(-/-) BMMs. Immunoprecipitation studies also indicated that the adaptor proteins DAP12/FcR gamma and Syk interacted with RANK during RANKL stimulation in BMMs in a manner. Phosphorylation of the DAP12/FcR gamma and the recruitment of Syk by DAP12/FcR gamma were suppressed in Fyn(-/-) BMMs. This is the first demonstration that Fyn relays the initial RANK/RANKL signal to the ITAM-containing adaptors DAP12/FcR gamma for OC differentiation. (c) 2012 Elsevier Inc. All rights reserved.