Department of Biochemistry, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
Arch Biochem Biophys. 2011 Feb 15;506(2):188-93. doi: 10.1016/j.abb.2010.11.011. Epub 2010 Nov 17.
High mobility group box 1 (HMGB1) initially identified as a non-histone chromosomal protein, which mainly functions as chromatin structure and transcriptional regulation, has been recently reported to be secreted into extracellular milieu in necrosis and apoptosis, and act as a proinflammatory mediator. However, the mechanism by which apoptotic cells release HMGB1 is not clear. In this study, we found that staurosporine (apoptosis-inducer)-induced HMGB1 release was associated with nucleosomal DNA fragmentation catalyzed by caspase-activated DNase (CAD) in WEHI-231 cells. Importantly, this event was effectively attenuated by the treatment of a pan-caspase inhibitor, Z-VAD-fmk, and by the inhibition of CAD-mediated DNA fragmentation by the expression of caspase-resistant inhibitor of CAD (ICAD-CR). In WEHI-231/ICAD-CR and WEHI-231/Puro cells, DNase γ-catalyzed nucleosomal DNA fragmentation occurred by anti-IgM antibody treatment was critical for HMGB1 release. Furthermore, in DNase γ stably-expressing HeLa S3 cells (HeLa S3/γ), the release of HMGB1 accompanied with nucleosomal DNA fragmentation was more apparent than that in parental HeLa S3 cells in which DNA fragmentation was scarcely observed. Taken together, these date suggest that nucleosomal DNA fragmentation catalyzed by CAD or DNase γ plays a pivotal role in HMGB1 release.
高迁移率族蛋白 B1（HMGB1）最初被鉴定为一种非组蛋白染色体蛋白，主要功能是作为染色质结构和转录调节物。最近的研究表明，HMGB1 在细胞坏死和凋亡时会被分泌到细胞外环境中，并作为一种促炎介质发挥作用。然而，凋亡细胞释放 HMGB1 的机制尚不清楚。在本研究中，我们发现，星形孢菌素（凋亡诱导剂）诱导的 HMGB1 释放与 caspase 激活的 DNA 酶（CAD）催化的核小体 DNA 片段化有关，在 WEHI-231 细胞中。重要的是，这一事件可以被泛半胱天冬酶抑制剂 Z-VAD-fmk 有效抑制，也可以通过表达半胱天冬酶抗性 CAD 抑制剂（ICAD-CR）抑制 CAD 介导的 DNA 片段化来有效抑制。在 WEHI-231/ICAD-CR 和 WEHI-231/Puro 细胞中，抗 IgM 抗体处理后 DNase γ 催化的核小体 DNA 片段化对于 HMGB1 的释放至关重要。此外，在 DNase γ 稳定表达的 HeLa S3 细胞（HeLa S3/γ）中，与在几乎观察不到 DNA 片段化的亲本 HeLa S3 细胞相比，HMGB1 释放伴随着核小体 DNA 片段化更为明显。总之，这些数据表明 CAD 或 DNase γ 催化的核小体 DNA 片段化在 HMGB1 释放中起关键作用。
