Influence of simulated microgravity on the activation of the small GTPase Rho involved in cytoskeletal formation--molecular cloning and sequencing of bovine leukemia-associated guanine nucleotide exchange factor.
Influence of simulated microgravity on the activation of the small GTPase Rho involved in cytoskeletal formation--molecular cloning and sequencing of bovine leukemia-associated guanine nucleotide exchange factor.
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DOI：
10.1186/1471-2091-7-19
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发表时间：
2006-06-28
期刊：
影响因子：
--
通讯作者：
Ishioka, Noriaki
中科院分区：
文献类型：
--
作者：
Higashibata, Akira;Imamizo-Sato, Mari;Seki, Masaya;Yamazaki, Takashi;Ishioka, Noriaki
在空间飞行实验细胞中，细胞骨架纤维的不规则形成已经被观察到，但纤维的解体过程仍然知之甚少。众所周知，小G T β Rho的激活导致肌动蛋白应力纤维组装。本研究旨在评估模拟微重力对细胞中参与肌动蛋白纤维重塑的Rho激活的影响。斜转影响肌动蛋白纤维的重塑及其相关的信号通路，涉及小GTdR Rho。肌动蛋白应力纤维重塑显着抑制在更大程度上在细胞培养下clinorotation比静态培养的细胞。从基因和蛋白表达分析，我们发现，白血病相关的Rho鸟嘌呤核苷酸交换因子（LARG），激活Rho，表达水平下调下回转。此外，我们确定了全长LARG cDNA。GTP结合的RhoA的量，即RhoA的活性形式，在此条件下减少。由三维回转器产生的模拟微重力影响了小GT_1-Rho的激活。此外，全长cDNA牛LARG，Rho鸟嘌呤核苷酸交换因子（GEF）家族的成员，被确定，其基因表达被观察到下clinrotation下调。这种下调随后导致RhoA激活的抑制。这些结果表明，肌动蛋白纤维的解体是由三维旋转抑制Rho激活引起的。
The irregular formation of cytoskeletal fibers in spaceflown experimental cells has been observed, but the disorganization process of fibers is still poorly understood. It is well known that the activation of the small GTPase Rho leads to actin stress fibers assembly. This study was performed to evaluate the effect of simulated microgravity on the activation of Rho that is involved in actin fiber remodeling in cells. Clinorotation influences actin fiber remodeling and its related signaling pathways that involve the small GTPase Rho. Actin stress fiber remodeling was significantly inhibited to a greater extent in cells cultured under clinorotation than in static cultured cells. From the gene and protein expression analyses, we found that the expression level of leukemia-associated Rho guanine nucleotide exchange factor (LARG), which activates Rho, was downregulated under clinorotation. Moreover, we identified the full-length LARG cDNA. The amount of GTP-bound RhoA, that is, the active form of RhoA, decreased under this condition. The activation of the small GTPase Rho was influenced by simulated microgravity generated by a three-dimensional (3D) clinostat. Furthermore, the full-length cDNA of bovine LARG, a member of the Rho guanine nucleotide exchange factor (GEF) family, was identified, and its gene expression was observed to be downregulated under clinorotation. This downregulation subsequently resulted in the repression of RhoA activation. These results indicated that the disorganization of the actin fibers was caused by the inhibition of Rho activation by 3D clinorotation.