Ras TRANSFORMATION OVERRIDES A PROLIFERATION DEFECT INDUCED BY Tpm3.1 KNOCKOUT
Ras TRANSFORMATION OVERRIDES A PROLIFERATION DEFECT INDUCED BY Tpm3.1 KNOCKOUT
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DOI：
10.1515/cmble-2015-0037
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发表时间：
2015-12-01
影响因子：
8.3
通讯作者：
Gunning, Peter W.
中科院分区：
文献类型：
--
作者：
Coombes, Jason D.;Schevzov, Galina;Gunning, Peter W.
肌动蛋白细胞骨架的广泛重组及其结合蛋白表达的变化是癌细胞的特征。之前我们已经证明，原肌球蛋白亚型 Tpm3.1 是肿瘤细胞中肌动蛋白细胞骨架的组成部分，是肿瘤细胞存活所必需的。我们的目标是确定缺乏 Tpm3.1 的癌细胞是否会逃避 H-Ras 转化诱导的致瘤效应。一系列癌细胞系的原肌球蛋白亚型 (Tpm) 表达谱 (21) 表明，Tpm3.1 是表达最广泛的 Tpm 亚型之一。因此，对 Tpm3.1 对转化过程的贡献进行了功能评估。从野生型 (WT) 和 Tpm3.1 敲除 (KO) 小鼠中分离的原代胚胎成纤维细胞用表达 SV40 大 T 抗原和 H-Ras 基因致癌等位基因 H-RasV12 的逆转录病毒载体转导，分别产生永生化和转化的 WT 和 KO MEF。我们发现 Tpm3.1 是 SV40 大 T 抗原永生化 MEF 中生长因子独立增殖所必需的，但这一要求可通过 H-Ras 转化克服。与这些发现一致的是，我们发现在小鼠模型中 Tpm3.1 不是锚定独立生长或 H-Ras 驱动肿瘤生长所必需的。最后，我们发现，相对于对照 MEF，pERK 和 Importin 7 蛋白相互作用在 SV40 大 T 抗原永生化 KO MEF 中显着降低，但在 H-Ras 转化的 KO 细胞中则没有。数据表明，H-Ras 转化超越了永生化 MEF 的生长因子独立增殖中对 Tpm3.1 的要求。我们认为，在 SV40 大 T 抗原永生化 MEF 中，Tpm3.1 部分负责 pERK 和 Imp7 之间的有效相互作用，从而导致细胞增殖，但这被 Ras 转化所覆盖。
Extensive re-organisation of the actin cytoskeleton and changes in the expression of its binding proteins is a characteristic feature of cancer cells. Previously we have shown that the tropomyosin isoform Tpm3.1, an integral component of the actin cytoskeleton in tumor cells, is required for tumor cell survival. Our objective was to determine whether cancer cells devoid of Tpm3.1 would evade the tumorgenic effects induced by H-Ras transformation. The tropomyosin isoform (Tpm) expression profile of a range of cancer cell lines (21) demonstrates that Tpm3.1 is one of the most broadly expressed Tpm isoform. Consequently, the contribution of Tpm3.1 to the transformation process was functionally evaluated. Primary embryonic fibroblasts isolated from wild type (WT) and Tpm3.1 knockout (KO) mice were transduced with retroviral vectors expressing SV40 large T antigen and an oncogenic allele of the H-Ras gene, H-RasV12, to generate immortalized and transformed WT and KO MEFs respectively. We show that Tpm3.1 is required for growth factor-independent proliferation in the SV40 large T antigen immortalized MEFs, but this requirement is overcome by H-Ras transformation. Consistent with those findings, we found that Tpm3.1 was not required for anchorage independent growth or growth of H-Ras-driven tumors in a mouse model. Finally, we show that pERK and Importin 7 protein interactions are significantly decreased in the SV40 large T antigen immortalized KO MEFs but not in the H-Ras transformed KO cells, relative to control MEFs. The data demonstrate that H-Ras transformation overrides a requirement for Tpm3.1 in growth factor-independent proliferation of immortalized MEFs. We propose that in the SV40 large T antigen immortalized MEFs, Tpm3.1 is partly responsible for the efficient interaction between pERK and Imp7 resulting in cell proliferation, but this is overidden by Ras transformation.