Chen Ling-Yu, Zuraw Bruce L, Ye Richard D, Pan Zhixing K
Department of Microbiology and Immunology, Medical College of Ohio, Toledo, Ohio 43614, USA.
J Biol Chem. 2004 Feb 20;279(8):7208-12. doi: 10.1074/jbc.M309542200. Epub 2003 Dec 1.
We reported previously that fMLP stimulates NF-kappaB activation, and this function of fMLP requires small GTPase RhoA in human peripheral blood monocytes (Huang, S., Chen, L.-Y., Zuraw, B. L., Ye, R. D., and Pan, Z. K. (2001) J. Biol. Chem. 276, 40977-40981). Here we present evidence that RhoA associates specifically with the guanine nucleotide exchange factor Lbc in human peripheral blood monocytes stimulated with fMLP and that Lbc specifically catalyzes the guanine nucleotide exchange activity of RhoA in human peripheral blood monocytes. Cotransfection of the monocytic THP1 cells with lbc with a kappaB promoter reporter plasmid results in a marked increase in NF-kappaB-mediated reporter gene expression. Finally, Lbc-enhanced NF-kappaB activation is inhibited by a RhoA inhibitor, C3 transferase from Clostridium botulinum. A dominant-negative form of RhoA (T19N) also inhibited Lbc-enhanced reporter gene expression in a kappaB-dependent manner. These results indicate that guanine nucleotide exchange factor Lbc is a novel signal transducer for RhoA-mediated NF-kappaB activation in human peripheral blood monocytes stimulated with bacterial products.
我们先前报道过，fMLP可刺激核因子-κB（NF-κB）的激活，且fMLP的这一功能在人外周血单核细胞中需要小GTP酶RhoA参与（Huang, S., Chen, L.-Y., Zuraw, B. L., Ye, R. D., and Pan, Z. K. (2001) J. Biol. Chem. 276, 40977 - 40981）。在此我们提供证据表明，在受fMLP刺激的人外周血单核细胞中，RhoA与鸟嘌呤核苷酸交换因子Lbc特异性结合，并且Lbc在人外周血单核细胞中特异性催化RhoA的鸟嘌呤核苷酸交换活性。单核细胞系THP1细胞与lbc和κB启动子报告质粒共转染，导致NF-κB介导的报告基因表达显著增加。最后，肉毒杆菌的RhoA抑制剂C3转移酶可抑制Lbc增强的NF-κB激活。显性负性形式的RhoA（T19N）也以κB依赖的方式抑制Lbc增强的报告基因表达。这些结果表明，鸟嘌呤核苷酸交换因子Lbc是细菌产物刺激的人外周血单核细胞中RhoA介导的NF-κB激活的一种新型信号转导分子。
