Ray Ramesh M, McCormack Shirley A, Covington Claire, Viar Mary Jane, Zheng Yi, Johnson Leonard R
Department of Physiology and Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
J Biol Chem. 2003 Apr 11;278(15):13039-46. doi: 10.1074/jbc.M208741200. Epub 2003 Feb 6.
The rapid migration of intestinal epithelial cells is important to the healing of mucosal ulcers and wounds. This cell migration requires the presence of polyamines and the activation of RhoA. RhoA activity, however, is not sufficient for migration because polyamine depletion inhibited the migration of IEC-6 cells expressing constitutively active RhoA. The current study examines the role of Rac1 and Cdc42 in cell migration and whether their activities are polyamine-dependent. Polyamine depletion with alpha-difluoromethylornithine inhibited the activities of RhoA, Rac1, and Cdc42. This inhibition was prevented by supplying exogenous putrescine in the presence of alpha-difluoromethylornithine. IEC-6 cells transfected with constitutively active Rac1 and Cdc42 migrated more rapidly than vector-transfected cells, whereas cells expressing dominant negative Rac1 and Cdc42 migrated more slowly. Polyamine depletion had no effect on the migration of cells expressing Rac1 and only partially inhibited the migration of those expressing Cdc42. Although polyamine depletion caused the disappearance of actin stress fibers in cells transfected with empty vector, it had no effect on cells expressing Rac1. Constitutively active Rac1 increased RhoA and Cdc42 activity in both normal and polyamine-depleted cells. These results demonstrate that Rac1, RhoA, and Cdc42 are required for optimal epithelial cell migration and that Rac1 activity is sufficient for cell migration in the absence of polyamines due to its ability to activate RhoA and Cdc42 as well as its own effects on the process of cell migration. These data imply that the involvement of polyamines in cell migration occurs either at Rac1 itself or upstream from Rac1.
肠道上皮细胞的快速迁移对黏膜溃疡和伤口的愈合很重要。这种细胞迁移需要多胺的存在以及RhoA的激活。然而，RhoA活性对于迁移并不足够，因为多胺耗竭会抑制表达组成型活性RhoA的IEC-6细胞的迁移。当前研究考察了Rac1和Cdc42在细胞迁移中的作用以及它们的活性是否依赖于多胺。用α-二氟甲基鸟氨酸进行多胺耗竭会抑制RhoA、Rac1和Cdc42的活性。在α-二氟甲基鸟氨酸存在的情况下供应外源性腐胺可防止这种抑制。转染了组成型活性Rac1和Cdc42的IEC-6细胞比载体转染细胞迁移得更快，而表达显性负性Rac1和Cdc42的细胞迁移得更慢。多胺耗竭对表达Rac1的细胞的迁移没有影响，仅部分抑制了表达Cdc42的细胞的迁移。尽管多胺耗竭导致用空载体转染的细胞中肌动蛋白应力纤维消失，但对表达Rac1的细胞没有影响。组成型活性Rac1在正常细胞和多胺耗竭细胞中均增加了RhoA和Cdc42的活性。这些结果表明，Rac1、RhoA和Cdc42是最佳上皮细胞迁移所必需的，并且由于Rac1能够激活RhoA和Cdc42以及其自身对细胞迁移过程的影响，在没有多胺的情况下Rac1活性足以支持细胞迁移。这些数据表明，多胺参与细胞迁移可能发生在Rac1本身或Rac1的上游。
