RalA and RalB: Antagonistic relatives in cancer cell migration
RalA and RalB: Antagonistic relatives in cancer cell migration
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DOI：
10.1158/0008-5472.can-04-1957
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发表时间：
2005-08-15
期刊：
影响因子：
11.2
通讯作者：
Theodorescu, D
中科院分区：
文献类型：
--
作者：
Oxford, G;Owens, CR;Theodorescu, D
小G蛋白的Ra1家族与肿瘤的发生、侵袭和转移有关。然而，由于Ra1A和Ra1B两种Ra1蛋白具有高度的序列同源性，因此很少有人重视阐明它们在这些过程中的单独作用。在这里，我们分析了Ra1A和Ra1B在两种人类癌细胞系中调节细胞迁移（侵袭性表型的必要组成部分）的单独贡献；UMUC-3是膀胱癌系，DUI45是前列腺癌系。虽然用两种不同的小干扰RNA双链抑制Ra1A蛋白表达约80%对迁移没有影响，但用两种不同的双链抑制相同程度的RalB表达导致迁移明显减少。抑制Ra1B表达确实会引发UMUC-3中肌动蛋白细胞骨架纤维的显著损失，而抑制Ra1A表达则未见此现象。有趣的是，同时抑制Ra1A和Ra1B的表达对迁移没有影响。然而，对UMUC-3中Ra1A和ROB表达的双重抑制确实导致肌动蛋白纤维几乎完全丧失以及增殖减少，特别是在血清减少的情况下。这些结果表明，Ra1A和Ra1B在细胞迁移中具有不同的作用，实际上它们可能作为这种表型的拮抗剂。为了进一步验证这一假设，我们发现本构活性Ra1A的表达抑制迁移，而本构活性Ra1B的表达促进迁移，与该模型一致。综上所述，我们首次证明，尽管Ra1A和Ra1B具有显著的序列同源性，但它们在癌细胞迁移中具有非重叠和相反的功能，但在细胞生长中具有重叠功能。
The Ra1 family of small G proteins has been implicated in tumorigenesis, invasion, and metastasis. However, little emphasis has been placed on clarifying the individual roles of the two Ra1 proteins, Ra1A and Ra1B, in these processes in view of their high sequence homology. Here we analyze the separate contributions of Ra1A and Ra1B in regulating cell migration, a necessary component of the invasive phenotype, in two human cancer cell lines; UMUC-3, a bladder carcinoma line, and the prostate carcinoma line, DUI45. Although inhibiting Ra1A protein expression by similar to 80% with two different small interfering RNA duplexes had no effect on migration, inhibiting RalB expression to the same extent with two different duplexes resulted in a marked reduction in migration. Inhibiting Ra1B expression did trigger a significant loss of actin cytoskeleton fibers in UMUC-3 that was not seen with inhibition of Ra1A expression. Interestingly, simultaneous inhibition of Ra1A and Ra1B expression had no effect on migration. However, dual inhibition of Ra1A and ROB expression in UMUC-3 did result in an almost total loss of actin fibers as well as a reduction in proliferation, particularly in reduced serum conditions. These results suggest that Ra1A and Ra1B have different roles in cell migration and that they may in fact act as antagonists with regard to this phenotype. As further verification of this hypothesis, we found that expression of constitutively active Ra1A inhibited migration, whereas expression of constitutively active Ra1B stimulated migration, consistent with this model. In summary, we present the first demonstration that despite their significant sequence homology, Ra1A and Ra1B have nonoverlapping and opposing functions in cancer cell migration but overlapping functions in cell growth.