Farnesyltransferase inhibitors reverse altered growth and distribution of actin filaments in Tsc-deficient cells via inhibition of both rapamycin-sensitive and -insensitive pathways
Farnesyltransferase inhibitors reverse altered growth and distribution of actin filaments in Tsc-deficient cells via inhibition of both rapamycin-sensitive and -insensitive pathways
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DOI：
10.1158/1535-7163.mct-04-0347
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发表时间：
2005-06-01
影响因子：
5.7
通讯作者：
Tamanoi, F
中科院分区：
文献类型：
--
作者：
Gau, CL;Kato-Stankiewicz, J;Tamanoi, F
法呢基转移酶抑制剂（FTI）已被开发为抗癌药物，目前正在临床试验中进行评估。在这项研究中，我们检查了 FTI 对 Tsc-null 细胞的影响，以深入了解它们对法尼基化 Rheb GTP 酶的影响。该蛋白参与 mTOR/S6K 信号传导的激活，并被 Tsc1/Tsc2 复合物下调。 Tsc1(-/-) 和 Tsc2(-/-) 小鼠胚胎成纤维细胞均表现出 S6K 的组成型激活，并在没有血清的情况下生长。两种不同的 FTI 化合物，临床化合物 BMS-214662 和新描述的 BMS-225975，抑制 mTOR/S6K 信号传导的组成型激活，并阻断 Tsc 缺失小鼠胚胎成纤维细胞的无血清生长。我们还发现 Tsc 缺失的小鼠胚胎成纤维细胞在不依赖贴壁的条件下生长，并且两种 FTI 化合物都会抑制这种软琼脂的生长。这些 FTI 效应与雷帕霉素观察到的效应相似。 Tsc 缺失的小鼠胚胎成纤维细胞的另一个有趣的表型是它们是圆形的，并且主要在细胞外围含有肌动蛋白丝。添加 FTI（而非雷帕霉素）导致细胞内肌动蛋白丝重新出现并导致外周肌动蛋白丝减少。 FTI 重排肌动蛋白丝的能力似乎主要是通过抑制 Rheb 蛋白介导的，因为在表达 Rheb (M184L) 的 Tsc2 缺失细胞中，FTI 诱导细胞内肌动蛋白丝的效率要低得多，Rheb (M184L 是一种可以绕过法呢基化的香叶基香叶基化突变体 Rheb)。这些结果表明，FTI 抑制 Rheb，在 Tsc 缺陷细胞中产生两种不同的影响，一种影响生长，另一种影响肌动蛋白丝分布。
Farnesyltransferase inhibitors (FTI) have been developed as anticancer drugs and are currently being evaluated in clinical trials. In this study, we have examined the effects of FTIs on Tsc-null cells to gain insight into their effects on farnesylated Rheb GTPase. This protein is involved in the activation of mTOR/S6K signaling and is down-regulated by the Tsc1/Tsc2 complex. Both Tsc1(-/-) and Tsc2(-/-) mouse embryonic fibroblasts exhibit constitutive activation of S6K and grow in the absence of serum. Two different FTI compounds, the clinical compound BMS-214662 and the newly described BMS-225975, inhibit the constitutive activation of mTOR/S6K signaling and block serum-free growth of the Tsc-null mouse embryonic fibroblasts. We have also found that Tsc-null mouse embryonic fibroblasts grow under anchorage-independent conditions and that both FTI compounds inhibit this soft agar growth. These FTI effects are similar to those observed with rapamycin. Another interesting phenotype of Tsc-null mouse embryonic fibroblasts is that they are round and contain actin filaments predominantly at the cell periphery. The addition of FTIs, but not rapamycin, led to the reappearance of intracellular actin filaments and reduction of peripheral actin filaments. The ability of FTI to rearrange actin filaments seems to be largely mediated by the inhibition of Rheb protein, as induction of intracellular actin filaments by FTI was much less efficient in Tsc2-null cells expressing Rheb (M184L), a geranylgeranylated mutant Rheb that can bypass farnesylation. These results reveal that FTIs inhibit Rheb, causing two different effects in Tsc-deficient cells, one on growth and the other on actin filament distribution.