This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Bacillus anthracis is the pathological agent causing anthrax, a disease that affects animals and humans. The lethal effect of systemic anthrax can be mimicked in animal models by the administration of anthrax lethal toxin (LT). LT is composed of two proteins: the protective antigen (PA) and the lethal factor (LF). PA binds to its receptor in all the cell types tested and promotes the entry of LF. LF exerts a cytolytic effect specific for macrophages. In vivo studies showed that macrophages mediate lethality since macrophagedepleted mice are resistant to LT. The molecular mechanism by which LT induces cell dead in susceptible macrophages is not clear. However, this process involves the inactivation of the p38 MAP kinase signaling pathway, through LT-mediated degradation of the p38 MAP kinase upstream activator MKK6. Macrophages in culture derived from inbred mouse strains show striking differences in their susceptibility LT. Genetic differences between susceptible and resistant strains have been mapped to the Kiftc gene, which encodes a kinesin-like motor protein. An association between Kif proteins and the p38 MAP kinase pathway has been previously documented in C. elegans and in mouse fibroblasts. Here we propose that resistance or susceptibility to anthrax LT in vivo is determined by the regulation of the p38 MAP kinase pathway by Kiflcin macrophages. To accomplish this we will: 1) determine whether the activation p38 MAP kinase is different in susceptible and resistant macrophages due to interactions of components of this pathway with specific Kif 1c forms; 2) test whether inactivation of the p38 MAP kinase pathway by LT in macrophages is required for lethality of susceptible strains in vivo; and 3) identify the proteins that are phosphorylated by p38 MAP kinase in resistant and susceptible macrophages by a proteomic study. This experimental approach will establish a detailed molecular model of the mechanism under laying susceptibility to LT-induced lethality
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