Departments of Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan; Cellular and Molecular Research Center, Ahvaz Jundishapur University of Medical Sciences, Iran.
J Neurosci Res. 2014 Apr;92(4):455-63. doi: 10.1002/jnr.23324. Epub 2014 Jan 20.
Activation of cdc42 reportedly enhances apoA-I-mediated cholesterol release through ATP-binding cassette transporter A1 (ABCA1). We examined the involvement of cdc42 and Rho kinase in intracellular cholesterol transport for release of cholesterol after the interaction between apoA-I and ABCA1 in astrocytes. Exogenously added apoA-I increased the GTP-bound form of cdc42 and enhanced Rho kinase activity in rat astrocytes. Suppression of ABCA1 expression by siRNA substantially repressed both cellular level of GTP-bound cdc42 and Rho kinase activity, indicating that these reactions require ABCA1. ApoA-I-mediated lipid release and Rho kinase activation were inhibited by not only Rho kinase inhibitor but also cdc42 siRNA. These findings suggest that cdc42 is activated by the interaction between apoA-I and ABCA1 and enhances cholesterol release through the activation of Rho kinase. ApoA-I increased the binding of Rock1, one of the Rho kinases, to reconstituted microtubule-like filaments (rMT). Y-27632 suppressed not only the association of rMT with the cytosolic lipid-protein particles (CLPP)-related proteins and lipids but also the intracellular transport of newly synthesized cholesterol to the plasma membrane in rat astrocytes treated with apoA-I without inhibiting cholesterol synthesis. Finally, cdc42 siRNA reduced apoA-I-induced interaction between rMT and major players in intracellular cholesterol trafficking, such as caveolin-1 and Rock1, suggesting a regulatory role of Rho family proteins in the apoA-I-mediated intracellular cholesterol transport. We conclude that ABCA1/cdc42/Rho kinase signaling is involved in apoA-I-induced intracellular cholesterol transport and apoA-I-mediated cholesterol release in rat astrocytes.
据报道，CDC42 的激活通过 ATP 结合盒转运体 A1（ABCA1）增强载脂蛋白 A-I 介导的胆固醇释放。我们研究了 cdc42 和 Rho 激酶在星形胶质细胞中载脂蛋白 A-I 与 ABCA1 相互作用后胆固醇细胞内转运和释放中的作用。外源性添加的载脂蛋白 A-I 增加了大鼠星形胶质细胞中 cdc42 的 GTP 结合形式，并增强了 Rho 激酶活性。siRNA 抑制 ABCA1 表达，大大抑制了细胞内 GTP 结合的 cdc42 和 Rho 激酶活性，表明这些反应需要 ABCA1。载脂蛋白 A-I 介导的脂质释放和 Rho 激酶激活不仅被 Rho 激酶抑制剂抑制，也被 cdc42 siRNA 抑制。这些发现表明，cdc42 是由载脂蛋白 A-I 与 ABCA1 的相互作用激活的，并通过激活 Rho 激酶增强胆固醇释放。载脂蛋白 A-I 增加了 Rho 激酶之一 Rock1 与重建的微管样丝（rMT）的结合。Y-27632 不仅抑制了 rMT 与胞质脂蛋白颗粒（CLPP）相关蛋白和脂质的结合，也抑制了新合成的胆固醇向用载脂蛋白 A-I 处理的大鼠星形胶质细胞的质膜的细胞内转运，而不抑制胆固醇合成。最后，cdc42 siRNA 减少了载脂蛋白 A-I 诱导的 rMT 与细胞内胆固醇转运的主要参与者之间的相互作用，如 caveolin-1 和 Rock1，表明 Rho 家族蛋白在载脂蛋白 A-I 介导的细胞内胆固醇转运中起调节作用。我们得出结论，ABCA1/cdc42/Rho 激酶信号通路参与了载脂蛋白 A-I 诱导的大鼠星形胶质细胞内胆固醇转运和载脂蛋白 A-I 介导的胆固醇释放。
