Department of Immunology and The Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA.
Proc Natl Acad Sci U S A. 2010 Dec 14;107(50):21629-34. doi: 10.1073/pnas.1016299107. Epub 2010 Nov 22.
The RNaseIII enzyme Dicer is required for mature microRNA production. Although extensive investigation has been carried out to determine the role of Dicer/miRNAs in the immune system, their function in mature CD8(+) T cells has not been examined. We deleted Dicer in mature polyclonal and TCR transgenic CD8(+) T cells using either tat-cre or the distal lck promoter, which drives cre expression after the stage of positive selection. Following antigenic challenge by a pathogen infection in vivo, Dicer-deleted CD8(+) T cells failed to accumulate at the usual peak of the response. Surprisingly however, we found that deletion of Dicer in mature CD8(+) T cells allowed them to respond more rapidly than control cells to TCR stimuli in vitro. In response to anti-CD3 plus anti-CD28 stimulation, Dicer-deleted T cells up-regulated CD69 faster and entered the first mitosis earlier than control T cells. In addition, activated Dicer(-/-) cells failed to rapidly down-regulate CD69 when removed from the TCR stimulus. As a probable consequence of this sustained CD69 expression, Dicer(-/-) T cells showed defective migration out of the central lymphoid organs in vivo. We identify miR-130/301, which are dramatically up-regulated following T-cell activation, as able to down-regulate CD69 expression via binding to a conserved site in the 3'UTR of CD69 mRNA. Thus, cellular functions dependent on Dicer expression are not required for the early steps in CD8(+) T-cell activation, but are essential for their survival and accumulation.
RNaseIII 酶 Dicer 是成熟 microRNA 产生所必需的。尽管已经进行了广泛的研究来确定 Dicer/miRNAs 在免疫系统中的作用，但它们在成熟的 CD8(+) T 细胞中的功能尚未被研究。我们使用 tat-cre 或远端 lck 启动子在成熟的多克隆和 TCR 转基因 CD8(+) T 细胞中删除 Dicer，后者在阳性选择后驱动 cre 表达。在体内通过病原体感染进行抗原挑战后，Dicer 缺失的 CD8(+) T 细胞未能在反应的通常高峰积聚。然而，令人惊讶的是，我们发现成熟的 CD8(+) T 细胞中 Dicer 的缺失允许它们比对照细胞更快地对体外 TCR 刺激做出反应。在对抗 CD3 和抗 CD28 的刺激下，Dicer 缺失的 T 细胞比对照 T 细胞更快地上调 CD69 的表达并更早地进入第一次有丝分裂。此外，当从 TCR 刺激中去除时，激活的 Dicer(-/-)细胞未能迅速下调 CD69。由于这种持续的 CD69 表达的可能后果，Dicer(-/-)T 细胞在体内显示出从中央淋巴器官中缺陷性迁移的缺陷。我们确定了 miR-130/301，其在 T 细胞激活后显著上调，可通过结合 CD69 mRNA 的 3'UTR 中的保守位点来下调 CD69 的表达。因此，依赖 Dicer 表达的细胞功能对于 CD8(+)T 细胞激活的早期步骤不是必需的，但对于它们的存活和积累是必需的。
