Increased susceptibility of spinal muscular atrophy fibroblasts to camptothecin is p53-independent.
Increased susceptibility of spinal muscular atrophy fibroblasts to camptothecin is p53-independent.
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DOI：
10.1186/1471-2121-10-40
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发表时间：
2009-05-16
期刊：
影响因子：
--
通讯作者：
Wang W
中科院分区：
文献类型：
--
作者：
Wu CY;Gómez-Curet I;Funanage VL;Scavina M;Wang W
运动神经元存活基因的缺失或突变(S)会导致脊髓性肌萎缩症(SMA)。已知SMN蛋白在RNA新陈代谢、轴突生长和细胞存活中发挥作用。然而，目前尚不清楚SMN缺乏如何导致SMA的选择性运动神经元死亡和肌肉萎缩。此前，我们已经证明SMA患者的皮肤成纤维细胞对DNA拓扑异构酶I抑制剂喜树碱更敏感，这支持SMN在细胞生存中的作用。在这里，我们研究了SMA成纤维细胞对喜树碱敏感性的潜在机制。喜树碱降低人成纤维细胞DNA拓扑异构酶I的DNA松弛活性。相反，DNA拓扑异构酶I的激酶活性不受喜树碱的影响，因为磷酸化SR蛋白的水平没有下降。经喜树碱治疗后，P53蛋白水平明显升高。为了确定P53是否在SMA成纤维细胞对喜树碱的敏感性增加中起作用，我们分析了SMA成纤维细胞对另一种DNA拓扑异构酶I抑制剂β-Lapachone的敏感性。已知这种化合物在几种癌细胞系中通过不依赖于P53的途径诱导死亡。我们发现β-拉帕酮不能诱导人成纤维细胞中P53的激活。此外，SMA和对照成纤维细胞对该化合物的敏感性基本相同。通过免疫荧光染色，SMN和P53共同定位于细胞核内的宝石中，这种共同定位在SMA成纤维细胞中总体上被减少。然而，siRNA缺失p53并不降低SMA成纤维细胞对喜树碱的敏感性。尽管P53和SMN相关，SMA成纤维细胞对喜树碱的敏感性增加并不是通过P53依赖的机制发生的。
Deletion or mutation(s) of the survival motor neuron 1 (SMN1) gene causes spinal muscular atrophy (SMA). The SMN protein is known to play a role in RNA metabolism, neurite outgrowth, and cell survival. Yet, it remains unclear how SMN deficiency causes selective motor neuron death and muscle atrophy seen in SMA. Previously, we have shown that skin fibroblasts from SMA patients are more sensitive to the DNA topoisomerase I inhibitor camptothecin, supporting a role for SMN in cell survival. Here, we examine the potential mechanism of camptothecin sensitivity in SMA fibroblasts. Camptothecin treatment reduced the DNA relaxation activity of DNA topoisomerase I in human fibroblasts. In contrast, kinase activity of DNA topoisomerase I was not affected by camptothecin, because levels of phosphorylated SR proteins were not decreased. Upon camptothecin treatment, levels of p53 were markedly increased. To determine if p53 plays a role in the increased sensitivity of SMA fibroblasts to camptothecin, we analyzed the sensitivity of SMA fibroblasts to another DNA topoisomerase I inhibitor, β-lapachone. This compound is known to induce death via a p53-independent pathway in several cancer cell lines. We found that β-lapachone did not induce p53 activation in human fibroblasts. In addition, SMA and control fibroblasts showed essentially identical sensitivity to this compound. By immunofluorescence staining, SMN and p53 co-localized in gems within the nucleus, and this co-localization was overall reduced in SMA fibroblasts. However, depletion of p53 by siRNA did not lessen the camptothecin sensitivity in SMA fibroblasts. Even though p53 and SMN are associated, the increased sensitivity of SMA fibroblasts to camptothecin does not occur through a p53-dependent mechanism.
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