Cancer Research Laboratory and Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, CA, USA.
Eur J Immunol. 2010 Jul;40(7):2041-9. doi: 10.1002/eji.200940231.
Nur77 orphan steroid receptor and its family member Nor-1 are required for apoptosis of developing T cells. In thymocytes, signals from the TCR complex induce Nur77 and Nor-1 expression followed by translocation from the nucleus to mitochondria. Nur77 and Nor-1 associate with Bcl-2 in the mitochondria, resulting in a conformation change that exposes the Bcl-2 BH3 domain, a presumed pro-apoptotic molecule of Bcl-2. As Nur77 and Nor-1 are heavily phosphorylated, we examined the requirement of Nur77 and Nor-1 phosphorylation in mitochondria translocation and Bcl-2 BH3 exposure. We found that HK434, a PKC agonist, in combination with calcium ionophore, can induce Nur77 and Nor-1 phosphorylation, translocation, Bcl-2 BH3 exposure and thymocyte apoptosis. Inhibitors of both classical and novel forms of PKC were able to block this process. In contrast, only the general but not classical PKC-specific inhibitors were able to block the same process initiated by PMA, a commonly used PKC agonist. These data demonstrate a differential activation of PKC isoforms by PMA and HK434 in thymocytes, and show the importance of PKC in mitochondria translocation of Nur77/Nor-1 and Bcl-2 conformation change during TCR-induced thymocyte apoptosis.
孤儿类固醇受体 Nur77 及其家族成员 Nor-1 是发育中的 T 细胞凋亡所必需的。在胸腺细胞中，T 细胞受体复合物的信号诱导 Nur77 和 Nor-1 的表达，随后从细胞核转位到线粒体。Nur77 和 Nor-1 在线粒体中与 Bcl-2 结合，导致构象变化，暴露出 Bcl-2 的 BH3 结构域，这是 Bcl-2 的一种假定的促凋亡分子。由于 Nur77 和 Nor-1 被高度磷酸化，我们研究了 Nur77 和 Nor-1 磷酸化在线粒体易位和 Bcl-2 BH3 暴露中的作用。我们发现，PKC 激动剂 HK434 与钙离子载体联合使用可以诱导 Nur77 和 Nor-1 的磷酸化、易位、Bcl-2 BH3 暴露和胸腺细胞凋亡。PKC 的经典和新型形式的抑制剂都能阻断这一过程。相比之下，只有一般而非经典的 PKC 特异性抑制剂能够阻断 PMA（一种常用的 PKC 激动剂）引发的相同过程。这些数据表明 PMA 和 HK434 在胸腺细胞中激活 PKC 同工酶的方式存在差异，并表明 PKC 在 TCR 诱导的胸腺细胞凋亡过程中对 Nur77/Nor-1 的线粒体易位和 Bcl-2 构象变化的重要性。
