Depletion of serum response factor by RNA interference mimics the mitogenic effects of platelet derived growth factor-BB in vascular smooth muscle cells
Depletion of serum response factor by RNA interference mimics the mitogenic effects of platelet derived growth factor-BB in vascular smooth muscle cells
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DOI：
10.1161/01.res.0000179776.40216.a9
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发表时间：
2005-09-02
影响因子：
20.1
通讯作者：
Nemenoff, RA
中科院分区：
文献类型：
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作者：
Kaplan-Albuquerque, N;Van Putten, V;Nemenoff, RA
许多平滑肌特异性基因（SM基因）的启动子含有多个CArG盒，其代表血清反应因子（SRF）的结合位点。通过这些区域的转录控制涉及与SRF和特定的辅激活因子如myocardin的相互作用。我们以前曾报道过，血小板衍生生长因子（PDGF）抑制SM基因表达与SRF的再分布有关，导致核内水平降低，SRF反式激活减少。为了进一步评估SRF耗竭对VSMC表型的作用，本研究使用RNA干扰（RNAi）。两个SRF特异性序列构建为发夹结构，在大鼠VSMC中稳定表达。表达SRF RNAi的克隆通过免疫印迹没有检测到SRF表达，并且显示SM α-肌动蛋白和启动子活性水平降低。出乎意料的是，VSMC的耗竭导致增殖和迁移速率增加。在缺乏SRF的细胞中，其表达通过PDGF刺激增加的几个基因，包括c-Jun，也被类似地诱导。SRF耗竭的影响不归因于PDGF受体活性的改变或Akt活化的改变。这些数据表明，在VSMC中SRF反式激活的丧失，在这种情况下通过RNAi抑制，诱导类似于用PDGF观察到的生物反应。
Promoters of many smooth muscle-specific genes (SM-genes) contain multiple CArG boxes, which represent a binding site for serum response factor (SRF). Transciptional control through these regions involves interactions with SRF and specific coactivators such as myocardin. We have previously reported that suppression of SM-gene expression by platelet derived growth factor ( PDGF) is associated with redistribution of SRF, leading to lower intra-nuclear levels, and a reduction in SRF transactivation. To further assess the role of SRF depletion on VSMC phenotype, the current study used RNA interference (RNAi). Two SRF-specific sequences constructed as hairpins were stably expressed in rat VSMC. Clones expressing SRF RNAi had no detectable SRF expression by immunoblotting, and showed diminished levels of SM alpha-actin protein and promoter activity. Unexpectedly, depletion of VSMC resulted in increased rates of proliferation and migration. Several genes whose expression is increased by PDGF stimulation, including c-Jun, were similarly induced in cells lacking SRF. Effects of SRF depletion were not attributable to altered PDGF receptor activity or alterations in activation of Akt. These data indicate that loss of SRF transactivation in VSMC, in this case through suppression via RNAi, induces biological responses similar to that seen with PDGF.