Cdc42 and Rac1 regulate late events in Salmonella typhimurium-induced interleukin-8 secretion from polarized epithelial cells
Cdc42 and Rac1 regulate late events in Salmonella typhimurium-induced interleukin-8 secretion from polarized epithelial cells
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DOI：
10.1074/jbc.m210466200
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发表时间：
2002-12-27
影响因子：
4.8
通讯作者：
Madara, JL
中科院分区：
文献类型：
--
作者：
Hobert, ME;Sands, KA;Madara, JL
鼠伤寒沙门菌在肠道上皮的定植引发病原体和宿主之间的生化交流，导致白细胞介素(IL)-8等趋化因子的分泌，直接中性粒细胞迁移到感染部位。在非极化细胞中，Rac1和Cdc42已被证明调节细菌入侵和导致核反应和IL-8分泌的信号事件。然而，由于潜在的肌动蛋白细胞骨架和相关的信号机制在极化上皮细胞中分布非常不同，我们使用极化的Madin-Darby犬肾单层来研究Rac1和Cdc42在鼠伤寒链球菌诱导的更生理相关的极化状态下的促炎反应中的作用。在表达显性阴性Rac1或Cdc42的Madin-Darby犬肾单分子层中，沙门氏菌和肿瘤坏死因子a诱导的NFkappaB和丝裂原激活的蛋白激酶信号级联反应正常进行，但IL-8的分泌受到抑制。我们发现Rac1和Cdc42不像在非极化细胞中那样参与早期的促炎信号事件，而是调节基底外侧的胞外分泌和IL-8的分泌。相反，显性阴性的Rac1抑制了顶端肌动蛋白基座的形成，表明基座的形成与促炎激活的核信号没有联系。这些发现表明，极化和非极化细胞对病原体诱导的宿主细胞信号通路的需求存在显著差异。
Salmonella typhimurium colonization of the intestinal epithelium initiates biochemical cross-talk between pathogen and host that results in the secretion of chemokines, such as interleukin (IL)-8, that direct neutrophil migration to the site of infection. In nonpolarized cells, Rac1 and Cdc42 have been shown to regulate both bacterial invasion and signaling events leading to nuclear responses and IL-8 secretion. However, because the underlying actin cytoskeleton and the associated signaling machinery are distributed much differently in polarized epithelial cells, we used polarized Madin-Darby canine kidney monolayers to investigate the role of Rac1 and Cdc42 in S. typhimurium-induced pro-inflammatory responses in the more physiologically relevant polarized state. In Madin-Darby canine kidney monolayers expressing dominant-negative Rac1 or Cdc42, both Salmonella- and tumor necrosis factor a-induced activation of NFkappaB and mitogen-activated protein kinase signaling cascades proceeded normally, but IL-8 secretion was inhibited. We found that Rac1 and Cdc42 were not involved in early pro-inflammatory signaling events, as in nonpolarized cells, but rather regulated the basolateral exocytosis and secretion of IL-8. In contrast, dominant-negative Rac1 inhibited apical actin pedestal formation, indicating that pedestal formation and nuclear signaling for pro-inflammatory activation are not linked. These findings indicate that there are significant differences in the requirements of pathogen-induced host cell signaling pathways in polarized and nonpolarized cells.