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Cécile Muller Iel-Soo Bang Jyoti Velayudhan Joyce Karlinsey Kai Papenfort Jörg Vogel Ferric C. Fang 《Molecular microbiology》2009,71(5):1228-1238
The alternative sigma factor σE is activated by unfolded outer membrane proteins (OMPs) and plays an essential role in Salmonella pathogenesis. The canonical pathway of σE activation in response to envelope stress involves sequential proteolysis of the anti-sigma factor RseA by the PDZ proteases DegS and RseP. Here we show that σE in Salmonella enterica sv. Typhimurium can also be activated by acid stress. A σE -deficient mutant exhibits increased susceptibility to acid pH and reduced survival in an acidified phagosomal vacuole. Acid activation of σE -dependent gene expression is independent of the unfolded OMP signal or the DegS protease but requires processing of RseA by RseP. The RseP PDZ domain is indispensable for acid induction, suggesting that acid stress may disrupt an inhibitory interaction between RseA and the RseP PDZ domain to allow RseA proteolysis in the absence of antecedent action of DegS. These observations demonstrate a novel environmental stimulus and activation pathway for the σE regulon that appear to be critically important during Salmonella –host cell interactions. 相似文献