Conditional knockout mice reveal an essential role of protein phosphatase 4 in thymocyte development and pre-T-cell receptor signaling
Conditional knockout mice reveal an essential role of protein phosphatase 4 in thymocyte development and pre-T-cell receptor signaling
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DOI：
10.1128/mcb.00799-06
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发表时间：
2007-01-01
影响因子：
5.3
通讯作者：
Tan, Tse-Hua
中科院分区：
文献类型：
--
作者：
Shui, Jr-Wen;Hu, Mickey C. -T.;Tan, Tse-Hua
冈田酸敏感丝氨酸/苏氨酸磷酸酶已被证明可调节白细胞介素-2转录和t细胞活化。冈田酸抑制蛋白磷酸酶4 (PP4)， PP4是一种与PP2A相关的新型丝氨酸/苏氨酸磷酸酶，其抑制浓度（IC50）与PP2A相当，为50%。这提出了一种可能性，即PP2A的一些细胞功能，实际上可能是PP4的功能，这些功能是通过使用冈田酸在T细胞中确定的。为了研究PP4在T细胞中的体内作用，我们制造了常规和T细胞特异性PP4条件敲除小鼠。我们发现PP4的消融导致小鼠胚胎死亡。t细胞谱系中PP4基因缺失导致胸腺细胞发育异常，包括t细胞在双阴性3期(CD4(-) CD8(-) CD25（+) CD44(-)）停滞，胸腺细胞异常成熟，阳性选择效果降低。体内pp4缺陷胸腺细胞增殖减少，凋亡增强。对t细胞前受体（pre-TCR）信号传导的分析进一步显示，在PP4缺失的情况下，钙通量和磷脂酶c - γ 1细胞外信号调节的激酶激活受损。在pp4缺陷小鼠中注射抗cd3导致胸腺细胞凋亡增强，伴凋亡前Bim增加，抗凋亡Bcl-xL蛋白水平降低。在外周，抗原特异性t细胞增殖和t细胞介导的免疫反应在pp4缺陷小鼠中显著受损。因此，我们的研究结果表明PP4对胸腺细胞发育和tcr前信号传导至关重要。
Okadaic acid-sensitive serine/threonine phosphatases have been shown to regulate interleukin-2 transcription and T-cell activation. Okadaic acid inhibits protein phosphatase 4 (PP4), a novel PP2A-related serine/threonine phosphatase, at a 50% inhibitory concentration (IC50) comparable to that for PP2A. This raises the possibility that some cellular functions of PP2A, determined in T cells by using okadaic acid, may in fact be those of PP4. To investigate the in vivo roles of PP4 in T cells, we generated conventional and T-cell-specific PP4 conditional knockout mice. We found that the ablation of PP4 led to the embryonic lethality of mice. PP4 gene deletion in the T-cell lineage resulted in aberrant thymocyte development, including T-cell arrest at the double-negative 3 stage (CD4(-) CD8(-) CD25(+) CD44(-)), abnormal thymocyte maturation, and lower efficacy of positive selection. PP4-deficient thymocytes showed decreased proliferation and enhanced apoptosis in vivo. Analysis of pre-T-cell receptor (pre-TCR) signaling further revealed impaired calcium flux and phosphollipase C-gamma 1-extracellular signal-regulated kinase activation in the absence of PP4. Anti-CD3 injection in PP4-deficient mice led to enhanced thymocyte apoptosis, accompanied by increased proapoptotic Bim but decreased antiapoptotic Bcl-xL protein levels. In the periphery, antigen-specific T-cell proliferation and T-cell-mediated immune responses in PP4-deficient mice were dramatically compromised. Thus, our results indicate that PP4 is essential for thymocyte development and pre-TCR signaling.