Ashida N, Arai H, Yamasaki M, Kita T
Department of Geriatric Medicine, Kyoto University Graduate School of Medicine, Kyoto, 606-8507, Japan.
J Biol Chem. 2001 May 11;276(19):16555-60. doi: 10.1074/jbc.M009068200. Epub 2001 Feb 7.
Transmigration of monocytes to the subendothelial space is the initial step of atherosclerotic plaque formation and inflammation. Integrin activation and chemotaxis are two important functions involved in monocyte transmigration. To delineate the signaling cascades leading to integrin activation and chemotaxis by monocyte chemoattractant protein-1 (MCP-1), we have investigated the roles of MAPK and Rho GTPases in THP-1 cells, a monocytic cell line. MCP-1 stimulated beta1 integrin-dependent, but not beta2 integrin-dependent cell adhesion in a time-dependent manner. MCP-1-mediated cell adhesion was inhibited by a MEK inhibitor but not by a p38-MAPK inhibitor. In contrast, MCP-1-mediated chemotaxis was inhibited by the p38-MAPK inhibitor but not by the MEK inhibitor. The inhibitor of Rho GTPase, C3 exoenzyme, and a Rho kinase inhibitor abrogated MCP-1-dependent chemotaxis but not integrin-dependent cell adhesion. Further, C3 exoenzyme and the Rho kinase inhibitor blocked MCP-1-dependent p38-MAPK activation. These data indicate that ERK is responsible for integrin activation, that p38-MAPK and Rho are responsible for chemotaxis mediated by MCP-1, and that Rho and the Rho kinase are upstream of p38-MAPK in MCP-1-mediated signaling. This study demonstrates that two distinct MAPKs regulate two dependent signaling cascades leading to integrin activation and chemotaxis induced by MCP-1 in THP-1 cells.
单核细胞迁移至内皮下间隙是动脉粥样硬化斑块形成和炎症的起始步骤。整合素激活和趋化作用是单核细胞迁移过程中涉及的两个重要功能。为了阐明单核细胞趋化蛋白-1（MCP-1）导致整合素激活和趋化作用的信号级联反应，我们研究了丝裂原活化蛋白激酶（MAPK）和Rho鸟苷三磷酸酶（GTPases）在单核细胞系THP-1细胞中的作用。MCP-1以时间依赖性方式刺激β1整合素依赖性而非β2整合素依赖性细胞黏附。MCP-1介导的细胞黏附受到MEK抑制剂的抑制，但不受p38丝裂原活化蛋白激酶抑制剂的抑制。相反，MCP-1介导的趋化作用受到p38丝裂原活化蛋白激酶抑制剂的抑制，但不受MEK抑制剂的抑制。Rho GTPase抑制剂C3外切酶和Rho激酶抑制剂消除了MCP-1依赖性趋化作用，但未消除整合素依赖性细胞黏附。此外，C3外切酶和Rho激酶抑制剂阻断了MCP-1依赖性p38丝裂原活化蛋白激酶的激活。这些数据表明，细胞外信号调节激酶（ERK）负责整合素激活，p38丝裂原活化蛋白激酶和Rho负责MCP-1介导的趋化作用，并且在MCP-1介导的信号传导中，Rho和Rho激酶位于p38丝裂原活化蛋白激酶的上游。本研究表明，两种不同的丝裂原活化蛋白激酶调节两个独立的信号级联反应，导致MCP-1在THP-1细胞中诱导的整合素激活和趋化作用。
