Protein phosphatase 2A has an essential role in promoting thymocyte survival during selection
Protein phosphatase 2A has an essential role in promoting thymocyte survival during selection
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蛋白磷酸酶 2A 在选择过程中促进胸腺细胞存活具有重要作用
DOI：
10.1073/pnas.1821116116
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发表时间：
2019-06-18
影响因子：
11.1
通讯作者：
Lu, Linrong
中科院分区：
文献类型：
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作者：
Zheng, Mingzhu;Li, Dan;Lu, Linrong
在发育中的胸腺细胞中，Ser/Thr磷酸化对于T细胞受体信号转导以及细胞存活/死亡调节至关重要。在这项工作中，我们建立了一个丝氨酸/苏氨酸磷酸化的胸腺细胞选择过程中。底物分析显示PP 2A是负责去磷酸化事件的最重要的酶，这在PP 2A cKO模型中得到了证实。胸腺特异性耗竭PP 2A导致胸腺细胞选择受损。PP 2A cKO后DP胸腺细胞的减少伴随着凋亡相关蛋白的去磷酸化失调和细胞凋亡增加，这可以通过Bcl 2转基因或p53敲除来挽救。这研究了PP 2A在胸腺细胞发育中的作用，并提供了通过去磷酸化调节胸腺相关分子来理解T细胞发育的见解。在胸腺中，胸腺细胞发育为成熟T细胞受到细胞选择的严格控制，其中只有一小部分配备有适当质量的TCR的胸腺细胞进展成熟。关键是保护通过选择的少数T细胞的存活。然而，保护胸腺中细胞存活的信号事件并不完全清楚。在这项研究中，蛋白质丝氨酸/苏氨酸磷酸化的胸腺细胞进行积极的选择是通过质谱分析。结果显示，在阳性选择过程中，T细胞受体（TCR）激活后发生了大量的去磷酸化变化。随后的底物分析确定蛋白磷酸酶2A（PP 2A）作为负责发育中胸腺细胞去磷酸化变化的酶。在Ppp 2caflox/Ppp-Lck-Cre小鼠（PP 2A cKO）中，T细胞谱系中的PP 2A催化亚基α（Ppp 2ca）缺失显示双阳性（DP）细胞中阿尔茨海默病相关蛋白的去磷酸化失调，并导致DP CD 4 + CD 8+细胞数量大幅减少。发现PP 2A cKO DP细胞中凋亡水平的增加是异常胸腺细胞发育的基础。最后，在PP 2A cKO小鼠中有缺陷的胸腺细胞发育可以通过Bcl 2转基因表达或通过p53敲除来挽救。总之，我们的工作揭示了PP 2A通过调节细胞存活在促进胸腺细胞发育中的重要作用。
Significance Ser/Thr phosphorylation is critical for T cell receptor signal transduction as well as cell survival/death regulation in developing thymocytes. In this work, we established a Ser/Thr phosphorylation profile during thymocytes selection. Substrate analysis revealed PP2A as the most important enzyme responsible for the dephosphorylation events, which was proved in the PP2A cKO model. Thymic-specific depletion of PP2A caused impaired thymocyte selection. The decrease of DP thymocytes upon PP2A cKO is accompanied by dysregulated dephosphorylation of apoptosis-related proteins and increased cell apoptosis, which could be rescued by Bcl2 transgene or p53 knockout. This studies the role of PP2A in thymocyte development and provides insights to understand T cell development through dephosphorylation regulation of apoptosis-related molecules. The development of thymocytes to mature T cells in the thymus is tightly controlled by cellular selection, in which only a small fraction of thymocytes equipped with proper quality of TCRs progress to maturation. It is pivotal to protect the survival of the few T cells, which pass the selection. However, the signaling events, which safeguard the cell survival in thymus, are not totally understood. In this study, protein Ser/Thr phosphorylation in thymocytes undergoing positive selection is profiled by mass spectrometry. The results revealed large numbers of dephosphorylation changes upon T cell receptor (TCR) activation during positive selection. Subsequent substrate analysis pinpointed protein phosphatase 2A (PP2A) as the enzyme responsible for the dephosphorylation changes in developing thymocytes. PP2A catalytic subunit α (Ppp2ca) deletion in the T cell lineage in Ppp2caflox/flox-Lck-Cre mice (PP2A cKO) displayed dysregulated dephosphorylation of apoptosis-related proteins in double-positive (DP) cells and caused substantially decreased numbers of DP CD4+ CD8+ cells. Increased levels of apoptosis in PP2A cKO DP cells were found to underlie aberrant thymocyte development. Finally, the defective thymocyte development in PP2A cKO mice could be rescued by either Bcl2 transgene expression or by p53 knockout. In summary, our work reveals an essential role of PP2A in promoting thymocyte development through the regulation of cell survival.