The K-Ras 4A isoform promotes apoptosis but does not affect either lifespan or spontaneous tumor incidence in aging mice
The K-Ras 4A isoform promotes apoptosis but does not affect either lifespan or spontaneous tumor incidence in aging mice
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DOI：
10.1016/j.yexcr.2005.10.004
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发表时间：
2006-01-01
影响因子：
3.7
通讯作者：
Patek, CE
中科院分区：
文献类型：
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作者：
Plowman, SJ;Arends, MJ;Patek, CE
Ras 蛋白在信号转导途径中充当分子开关，在这里，我们通过将野生型胚胎干 (ES) 细胞与仅表达 K-ras4B 的 K-ras(tm Delta 4A/tm Delta 4A)（外显子 4A 敲除）ES 细胞和 K-ras(-/-)（外显子 1 - 3 敲除）ES 细胞进行比较，检查了 K-ras4A 和 413 剪接变体对细胞功能的影响。不表达剪接变体的细胞以及来自野生型和K-ras(tm Delta 4A/tm Delta 4A)小鼠的肠上皮。 RT-qPCR 分析发现，K-ras(tm Delta 4A/tm Delta 4A) ES 细胞中 K-ras4B 表达降低，但小肠中不受影响。 K-Ras缺乏不影响ES细胞生长，K-Ras4A缺乏不影响肠上皮增殖。 K-ras(tm Delta 4A/tm Delta 4A)和K-ras(-/-) ES细胞在LIF撤除后表现出分化能力降低，并且K-ras(-/-)细胞分化程度最低。 K-Ras4A 缺陷抑制依托泊苷诱导的 ES 细胞和肠上皮细胞凋亡。然而，K-ras(tm Delta 4A/tm Delta 4A) ES 细胞比 K-ras(-/-) 细胞更能抵抗依托泊苷诱导的细胞凋亡。结果表明（1）K-Ras4A 促进细胞凋亡，而 K-Ras4B 抑制细胞凋亡；（2）K-Ras4B（可能还有 K-Ras4A）促进分化。这些发现提出了这样一种可能性：K-Ras4A4B 亚型比例的改变通过差异性影响干细胞存活和/或分化来调节肿瘤发生。然而，K-Ras4A 缺陷并不影响衰老小鼠的预期寿命或自发性总体肿瘤发生率。 (c) 2005 Elsevier Inc. 保留所有权利。
Ras proteins function as molecular switches in signal transduction pathways, and, here, we examined the effects of the K-ras4A and 413 splice variants on cell function by comparing wild-type embryonic stem (ES) cells with K-ras(tm Delta 4A/tm Delta 4A) (exon 4A knock-out) ES cells which express K-ras4B only and K-ras(-/-) (exons 1 - 3 knock-out) ES cells which express neither splice variant, and intestinal epithelium from wild-type and K-ras(tm Delta 4A/tm Delta 4A) mice. RT-qPCR analysis found that K-ras4B expression was reduced in K-ras(tm Delta 4A/tm Delta 4A) ES cells but unaffected in small intestine. K-Ras deficiency did not affect ES cell growth, and K-Ras4A deficiency did not affect intestinal epithelial proliferation. K-ras(tm Delta 4A/tm Delta 4A) and K-ras(-/-) ES cells showed a reduced capacity for differentiation following LIF withdrawal, and K-ras(-/-) cells were least differentiated. K-Ras4A deficiency inhibited etoposide-induced apoptosis in ES cells and intestinal epithelial cells. However, K-ras(tm Delta 4A/tm Delta 4A) ES cells were more resistant to etoposide-induced apoptosis than K-ras(-/-) cells. The results indicate that (1) K-Ras4A promotes apoptosis while K-Ras4B inhibits it, and (2) K-Ras4B, and possibly K-Ras4A, promotes differentiation. The findings raise the possibility that alteration of the K-Ras4A4B isoform ratio modulates tumorigenesis by differentially affecting stem cell survival and/or differentiation. However, K-Ras4A deficiency did not affect life expectancy or spontaneous overall tumor incidence in aging mice. (c) 2005 Elsevier Inc. All rights reserved.