RESUMO
Dam methylation is an essential factor involved in the virulence of an increasing number of bacterial pathogens including Salmonella enterica. Lack of Dam methylation causes severe attenuation in animal models. It has been proposed that dysregulation of Dam activity is potentially a general strategy for the generation of vaccines against bacterial pathogens. In this review, we focus our attention on the role of methylation by Dam protein in regulating bacterial gene expression and virulence in Salmonella enterica.
Assuntos
Salmonella enterica/patogenicidade , DNA Metiltransferases Sítio Específica (Adenina-Específica)/fisiologia , Fatores de Virulência/fisiologia , Animais , Modelos Animais de Doenças , Regulação Bacteriana da Expressão Gênica , Modelos Biológicos , Salmonelose Animal/microbiologia , Vacinas contra Salmonella/genética , Vacinas contra Salmonella/imunologia , Salmonella enterica/citologia , Salmonella enterica/enzimologia , Salmonella enterica/fisiologia , DNA Metiltransferases Sítio Específica (Adenina-Específica)/deficiência , Vacinas Atenuadas/genética , Vacinas Atenuadas/imunologia , Virulência , Fatores de Virulência/deficiênciaRESUMO
Although dam mutants of Salmonella have been proposed as live vaccines, their capacity to trigger cell inflammatory cascades has not been fully elucidated. We investigated in detail the ability of Salmonella enterica dam mutant to activate the signalling pathways of the inflammatory response in RAW 264.7 cells. Apoptosis in macrophages treated with Salmonella dam mutant was low. Similarly, the expression of both NOS-2 and COX-2 and subsequently the production of NO and PGE(2) was significantly reduced. Also, Salmonella dam mutant induced an attenuated activation of the inflammatory signalling pathway as indicated by the reduced degradation of IkappaBalpha and IkappaBbeta and the low IkappaBalpha phosphorylation found. In addition, translocation of p65 to the nucleus was notably impaired and the amount of phosphorylated p44, p42 and p38 MAPKs was clearly reduced in extracts from dam-infected macrophages. These results indicate that the lack of ERK and p38 phosphorylation at the proper time in dam-infected cells notably reduces the engagement of subsequent signalling pathways involved in the full activation of NF-kappaB in response to infection. Taken together, these results suggest that Salmonella activation of both signalling cascades in the inflammatory response is a mechanism requiring Dam protein participation.