Zhang Yue, Ting Adrian T, Marcu Kenneth B, Bliska James B
Department of Molecular Genetics and Microbiology, and Center for Infectious Diseases, Institute for Cell and Developmental Biology, State University of New York, Stony Brook, NY 11794, USA.
J Immunol. 2005 Jun 15;174(12):7939-49. doi: 10.4049/jimmunol.174.12.7939.
Macrophages respond to infection with pathogenic Yersinia species by activating MAPK- and NF-kappaB-signaling pathways. To counteract this response, Yersiniae secrete a protease (Yersinia outer protein J (YopJ)) that is delivered into macrophages, deactivates MAPK- and NF-kappaB-signaling pathways, and induces apoptosis. NF-kappaB promotes cell survival by up-regulating expression of several apoptosis inhibitor genes. Previous studies show that deactivation of the NF-kappaB pathway by YopJ is important for Yersinia-induced apoptosis. To determine whether deactivation of the NF-kappaB pathway is sufficient for Yersinia-induced apoptosis, two inhibitors of the NF-kappaB pathway, IkappaBalpha superrepressor or A20, were expressed in macrophages. Macrophages expressing these proteins were infected with Yersinia pseudotuberculosis strains that secrete functionally active or inactive forms of YopJ. Apoptosis levels were substantially higher (5- to 10-fold) when active YopJ was delivered into macrophages expressing IkappaBalpha superrepressor or A20, suggesting that deactivation of the NF-kappaB pathway is not sufficient for rapid Yersinia-induced apoptosis. When macrophages expressing A20 were treated with specific inhibitors of MAPKs, similar levels of apoptosis (within approximately 2-fold) were observed when active or inactive YopJ were delivered during infection. These results suggest that MAPK and NF-kappaB pathways function together to up-regulate apoptosis inhibitor gene expression in macrophages in response to Yersinia infection and that YopJ deactivates both pathways to promote rapid apoptosis. In addition, treating macrophages with a proteasome inhibitor results in higher levels of infection-induced apoptosis than can be achieved by blocking NF-kappaB function alone, suggesting that proapoptotic proteins are stabilized when proteasome function is blocked in macrophages.
巨噬细胞通过激活丝裂原活化蛋白激酶（MAPK）和核因子κB（NF-κB）信号通路来应对致病性耶尔森菌属的感染。为了对抗这种反应，耶尔森菌分泌一种蛋白酶（耶尔森菌外蛋白J（YopJ）），该蛋白酶被递送到巨噬细胞中，使MAPK和NF-κB信号通路失活，并诱导细胞凋亡。NF-κB通过上调几种凋亡抑制基因的表达来促进细胞存活。先前的研究表明，YopJ使NF-κB通路失活对耶尔森菌诱导的细胞凋亡很重要。为了确定NF-κB通路的失活是否足以导致耶尔森菌诱导的细胞凋亡，在巨噬细胞中表达了两种NF-κB通路抑制剂，即IκBα超级阻遏物或A20。表达这些蛋白的巨噬细胞用分泌功能活性或无活性形式YopJ的假结核耶尔森菌菌株进行感染。当活性YopJ被递送到表达IκBα超级阻遏物或A20的巨噬细胞中时，细胞凋亡水平显著更高（5至10倍），这表明NF-κB通路的失活不足以导致快速的耶尔森菌诱导的细胞凋亡。当用MAPK的特异性抑制剂处理表达A20的巨噬细胞时，在感染期间递送活性或无活性YopJ时观察到相似水平的细胞凋亡（约2倍以内）。这些结果表明，MAPK和NF-κB通路共同发挥作用，上调巨噬细胞中凋亡抑制基因的表达以应对耶尔森菌感染，并且YopJ使这两条通路失活以促进快速细胞凋亡。此外，用蛋白酶体抑制剂处理巨噬细胞会导致比单独阻断NF-κB功能更高水平的感染诱导的细胞凋亡，这表明当巨噬细胞中蛋白酶体功能被阻断时，促凋亡蛋白会被稳定下来。
