Nakatomi Kota, Ueno Hikari, Ishikawa Yuto, Salim Ronny Christiadi, Mori Yuki, Kanemoto Issey, Tancharoen Salunya, Kikuchi Kiyoshi, Miura Naoki, Omori Taketo, Okuda-Ashitaka Emiko, Matsumura Kiyoshi, Imaizumi Hitoshi, Motomiya Yoshihiro, Maruyama Ikuro, Kawahara Ko-Ichi
Department of Biomedical Engineering, Osaka Institute of Technology, Osaka 535-8585, Japan.
Department of Pharmacology, Faculty of Dentistry, Mahidol University, Bangkok 10400, Thailand.
Biomed Rep. 2021 Feb;14(2):21. doi: 10.3892/br.2020.1397. Epub 2020 Dec 2.
Nucleophosmin 1 (NPM1) primarily localizes to the nucleus and is passively released into the extracellular milieu by necrotic or damaged cells, or is secreted by monocytes and macrophages. Extracellular NPM1 acts as a potent inflammatory stimulator by promoting cytokine production [e.g., tumor necrosis factor-α (TNF-α)], which suggests that NPM1 acts as a damage-associated molecular pattern. However, the receptor of NPM1 is unknown. Evidence indicates that DAMPs, which include high mobility group box 1 and histones, may bind Toll-like receptors (TLRs). In the present study, it was shown that NPM1 signaling was mediated via the TLR4 pathway, which suggests that TLR4 is an NPM1 receptor. TLR4 binds myeloid differentiation protein-2 (MD-2), which is essential for intracellular signaling. Furthermore, the TLR4 antagonist, LPS- (an MD-2 antagonist) and TAK-242 (a TLR4 signaling inhibitor) significantly inhibited NPM1-induced TNF-α production by differentiated THP-1 cells as well as reducing ERK1/2 activation. Far-western blot analysis revealed that NPM1 directly bound MD-2. Thus, the results of the present study provide compelling evidence that TLR4 binds NPM1, and it is hypothesized that inhibiting NPM1 activity may serve as a novel strategy for treating TLR4-related diseases.
核磷蛋白1（NPM1）主要定位于细胞核，可通过坏死或受损细胞被动释放到细胞外环境中，或由单核细胞和巨噬细胞分泌。细胞外NPM1通过促进细胞因子产生[如肿瘤坏死因子-α（TNF-α）]而作为一种强效炎症刺激物，这表明NPM1作为一种损伤相关分子模式发挥作用。然而，NPM1的受体尚不清楚。有证据表明，包括高迁移率族蛋白盒1和组蛋白在内的损伤相关分子模式（DAMPs）可能与Toll样受体（TLRs）结合。在本研究中，结果表明NPM1信号是通过TLR4途径介导的，这表明TLR4是NPM1的受体。TLR4与髓样分化蛋白2（MD-2）结合，而MD-2对细胞内信号传导至关重要。此外，TLR4拮抗剂LPS-（一种MD-2拮抗剂）和TAK-242（一种TLR4信号抑制剂）显著抑制分化的THP-1细胞中NPM1诱导的TNF-α产生，并降低ERK1/2激活。Far-western印迹分析显示NPM1直接与MD-2结合。因此，本研究结果提供了令人信服的证据，证明TLR4与NPM1结合，并且据推测抑制NPM1活性可能作为治疗TLR4相关疾病的一种新策略。
