プロテオーム解析によるサルモネラ病原因子の同定

抄録

During infection of mammalian hosts, Salmonella enterica serovar Typhimurium, a facultative intracellular pathogen, has to adjust rapidly to different environmental conditions encountered during passage through the gastrointestinal tract and following uptake into epithelial cells and macrophages. Successful establishment within the host therefore requires the coordinated expression of a large number of virulence genes necessary for the adaptation between the extracellular and intracellular phases of infection. The stringent response is a global bacterial response to nutritional stress that is mediated by accumulation of the alarmone guanosine tetraphosphate (ppGpp). It has been reported that ppGpp is required for the expression of nearly all known S. enterica virulence genes. However, the function of many proteins that are annotated on the genome of S. enterica serovar Typhimurium are still putative or unknown, and the complicated regulatory mechanism of the virulence by ppGpp is not well understood. Here, we constructed an agarose 2-dementinal electrophoresis reference map of S. enterica serovar Typhimurium strain ATCC 14028 for an exhaustive identification of ppGpp-regulated genes. We successfully identified 320 proteins on the reference map, and 155 proteins including a number of known virulence factors, which are more highly expressed in S. enterica serovar Typhimurium wild-type strain than the ppGpp0 mutant strain by comparative proteomics. Furthermore, using a mouse model of infection, two proteins, STM3169 and STM4242, were identified as novel virulence factors required for the complete mouse systemic infection by Salmonella. These results provide unequivocal evidence of the role of ppGpp in Salmonella virulence.