Vier Juliane, Häcker Georg, Kirschnek Susanne
Institute of Medical Microbiology and Hygiene, Medical Center, University of Freiburg, Faculty of Medicine, Freiburg, Germany.
Cell Death Dis. 2024 Sep 16;15(9):677. doi: 10.1038/s41419-024-07064-z.
Myeloid cells are the first line of defence against pathogens. Mitochondrial apoptosis signalling is a crucial regulator of myeloid cell lifespan and modulates the function of myeloid cells. The anti-apoptotic protein BCL-2-family protein BCL2A1/A1/BFL-1 is strongly upregulated in inflammation in macrophages. We analysed the contribution of A1 to apoptosis regulation in a conditional system of in vitro differentiation of murine macrophages from immortalised progenitors. We disabled the expression of A1 by targeting all murine A1 isoforms in the genome. Specific inhibitors were used to inactivate other anti-apoptotic proteins. Macrophage progenitor survival mainly depended on the anti-apoptotic proteins MCL-1, BCL-X and A1 but not BCL-2. Deletion of A1 on its own had little effect on progenitor cell survival but was sensitised to cell death induction when BCL-X or MCL-1 was neutralised. In progenitors, A1 was required for survival in the presence of the inflammatory stimulus LPS. Differentiated macrophages were resistant to inhibition of single anti-apoptotic proteins, but A1 was required to protect macrophages against inhibition of either BCL-X or MCL-1; BCL-2 only had a minor role in these cells. Cell death by neutralisation of anti-apoptotic proteins completely depended on BAX with a small contribution of BAK only in progenitors in the presence of LPS. A1 and NOXA appeared to stabilise each other at the posttranscriptional level suggesting direct binding. Co-immunoprecipitation experiments showed the binding of A1 to NOXA and BIM. Interaction between A1 and Noxa may indirectly prevent neutralisation and destabilization of MCL-1. Our findings suggest a unique role for A1 as a modulator of survival in the macrophage lineage in concert with MCL-1 and BCL-X, especially in a pro-inflammatory environment.
髓系细胞是抵御病原体的第一道防线。线粒体凋亡信号传导是髓系细胞寿命的关键调节因子，并调节髓系细胞的功能。抗凋亡蛋白BCL-2家族蛋白BCL2A1/A1/BFL-1在巨噬细胞炎症中强烈上调。我们在一个从永生化祖细胞体外分化小鼠巨噬细胞的条件系统中分析了A1对凋亡调节的作用。我们通过靶向基因组中的所有小鼠A1异构体来使A1的表达失活。使用特异性抑制剂来使其他抗凋亡蛋白失活。巨噬细胞祖细胞的存活主要依赖于抗凋亡蛋白MCL-1、BCL-X和A1，而不是BCL-2。单独缺失A1对祖细胞存活影响不大，但当BCL-X或MCL-1被中和时，对细胞死亡诱导敏感。在祖细胞中，在存在炎症刺激脂多糖（LPS）的情况下，A1是存活所必需的。分化的巨噬细胞对单一抗凋亡蛋白的抑制具有抗性，但需要A1来保护巨噬细胞免受BCL-X或MCL-1抑制的影响；BCL-2在这些细胞中仅起次要作用。通过中和抗凋亡蛋白导致的细胞死亡完全依赖于BAX，只有在存在LPS的祖细胞中BAK有小部分作用。A1和NOXA似乎在转录后水平相互稳定，提示直接结合。免疫共沉淀实验显示A1与NOXA和BIM结合。A1与Noxa之间的相互作用可能间接防止MCL-1的中和与失稳。我们的研究结果表明，A1作为巨噬细胞谱系中与MCL-1和BCL-X协同的存活调节因子具有独特作用，特别是在促炎环境中。
