Role of Mitofusin-2 in High Mobility Group Box-1 Protein-Mediated Apoptosis of T Cells in Vitro

• Published in: Cellular physiology and biochemistry Vol. 33; no. 3; pp. 769 - 783
• Main Authors: Wu, Zong-sheng, Yao, Yong-ming, Hong, Guang-liang, Xu, Xiu-ping, Liu, Yao, Dong, Ning, Zheng, Jia-yi, Lu, Zhong-qiu, Zhao, Guang-ju, Zhu, Xiao-mei, Zhang, Qing-hong, Sheng, Zhi-yong
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland Cell Physiol Biochem Press GmbH & Co KG 01.01.2014
• Subjects: Apoptosis; Apoptosis - immunology; Calcium; Calcium Signaling - immunology; Caspases - immunology; GTP Phosphohydrolases - immunology; High mobility group box-1 protein (HMGB1); HMGB1 Protein - immunology; Humans; Jurkat Cells; Jurkat T cells; Mitochondrial Proteins - immunology; Mitofusin-2(Mfn2); Original Paper; T-Lymphocytes - immunology; High mobility group box-1 protein (HMGB1); Jurkat T cells; Calcium; Mitofusin-2(Mfn2); Apoptosis
• ISSN: 1015-8987; 1421-9778
• DOI: 10.1159/000358651

Background: High mobility group box-1 protein (HMGB1), a ubiquitous nuclear protein, which is recognized as a danger-associated molecular pattern (DAMP) triggering activation of the innate immune system. Previous studies have shown that HMGB1 also plays a role in T cell-mediated immunity, but the effect of HMGB1 on apoptosis of T cells and its precise mechanism remain to be determined. Methods: Two kinds of apoptosis assay techniques were used, i.e., Annexin V-FITC conjunction with PI to identify early apoptotic cells, Hoechst 33342 staining for double-stranded DNA to observe nuclear fragmentation or apoptotic body. The activation status of caspase-3, caspase-8, as well as caspase-9 was examined by colorimetric assay. The dynamic changes in intracellular calcium concentration ([Ca 2+ ] i ) was monitored by flow cytometry. Overexpression of Mfn2 was preformed by lentiviral vector transfection. The mRNA and protein levels of Mfn2 were determined by RT-PCR and Western-blotting. Results: Treatment of Jurkat T cells with recombinant human HMGB1 (rhHMGB1) causes a significant dose-dependent increase in percentage of apoptotic cells. When T cells are incubated with HMGB1 they express decreased mitochondria fusion-related protein mitofusin-2 (Mfn2) and activate mitochondrial apoptotic pathway via elevation of [Ca 2+ ] i , Bax insertion, and activation of caspase. Furthermore, overexpression of Mfn2 ameliorates the apoptosis of T cells induced by HMGB1. This occurs at least partly through Mfn2 keeps Ca 2+ homeostasis in T cells evidenced by monitoring [Ca 2+ ] i dynamics. Conclusion: HMGB1 can trigger apoptosis of T lymphocytes through mitochondrial death pathway associated with [Ca 2+ ] i elevation. Mfn2 plays a pivotal role in this process, and it might be a novel therapeutic target in T cell apoptosis related disorders.