Molecular mechanisms implicated in galectin-1-induced apoptosis: activation of the AP-1 transcription factor and downregulation of Bcl-2
Molecular mechanisms implicated in galectin-1-induced apoptosis: activation of the AP-1 transcription factor and downregulation of Bcl-2
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DOI：
10.1038/sj.cdd.4400708
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发表时间：
2000-08-01
影响因子：
12.4
通讯作者：
Riera, CM
中科院分区：
文献类型：
--
作者：
Rabinovich, GA;Alonso, CR;Riera, CM
半乳糖凝集素是一类具有特异性免疫调节作用的新型生物活性分子。半乳糖凝集素-1（Galectin-1，Gal-1）是该家族的成员，已被证明可诱导成熟T细胞和未成熟胸腺细胞的凋亡。为了深入了解Gal-1与成熟T细胞结合后转导的细胞内信号，我们研究了这种蛋白质是否触发了二聚体AP-1转录因子的激活。当T细胞在Gal-1存在下培养30分钟时，通过电泳迁移率变动分析可以检测到核提取物与含有AP-1共有序列的合成寡核苷酸的结合的显著增加。通过北方印迹分析确定，在此DNA结合活性之前，c-Jun mRNA水平快速增加。当细胞在暴露于Gal-1之前用姜黄素（AP-1活化的抑制剂）预处理时，通过观察到的DNA片段化水平的剂量依赖性降低证实了AP-1对Gal-1诱导的细胞凋亡的需求。最后，通过Western印迹分析也提供了证据，表明Gal-1抑制刀豆球蛋白A（ConA）对Bcl-2蛋白的诱导。本研究的结果提供了关于AP-1和Bcl-2作为Gal-1触发的信号转导通路的靶点的第一个实验证据，并为更深入地理解T细胞死亡调节的分子机制奠定了基础。
Galectins are emerging as a new class of bioactive molecules with specific immunomodulatory properties. Galectin-1 (Gal-1), a member of this family, has been shown to induce apoptosis of mature T cells and immature thymocytes. To gain insight into the Intracellular signals transduced by Gal-1 upon binding to mature T cells, we investigated whether this protein triggered activation of the dimeric AP-1 transcription factor. A marked increase in the binding of nuclear extracts to synthetic oligonucleotides containing the AP-1 consensus sequence, could be detected by an electrophoretic mobility shift assay, when T cells were cultured for 30 min in the presence of Gal-1. This DNA-binding activity was preceded by a rapid increase in the levels of c-Jun mRNA, as determined by Northern blot analysis. Requirement of AP-1 for Gal-1-induced apoptosis was confirmed by the dose-dependent reduction on the level of DNA fragmentation observed when cells were pre-treated with curcumin (an inhibitor of AP-1 activation) before exposure to Gal-1. Finally, evidence is also provided by Western blot analysis, showing that Gal-1 inhibits Concanavalin A (Con A) induction of Bcl-2 protein. Results presented in this study provide the first experimental evidence regarding AP-1 and Bcl-2 as targets of the signal transduction pathway triggered by Gal-1 and set the basis for a more in depth understanding of the molecular mechanisms of T-cell death regulation.