Cytolocalization of the PhoP response regulator in Salmonell enterica: moculation by extracellular Mg 2+ and by the SCV environment.

SCIARA MI; SPAGNUOLO C; JARES-ERIJMAN E; GARCÍA VÉSCOVI, E.

MOLECULAR MICROBIOLOGY

Oxford, OX ; Boston, MA : Blackwell Scientific Publications, c1987

Año: 2008 vol. 70 p. 479 - 493

0950-382X

Summary The PhoP/PhoQ two-component system plays an essential role regulating numerous virulence phenotypes in Salmonella enterica. Previous work showed that PhoQ, the sensor protein, switches between the kinase- and the phosphatase-dominant state in response to environmental Mg2+ availability. This switch defines the PhoP phosphorylation status and, as a result, the transcriptional activity of this regulator. In this work, using the FlAsH labeling technique, we examine PhoP cytolocalization in response to extracellular Mg2+ limitation in vitro and to the SCV environment in macrophage cells. We demonstrate that in these PhoP/PhoQ-inducing environments PhoP displays preferential localization to one cell pole, while being homogeneously distributed in the bacterial cytoplasm in repressing conditions. Polar localization is lost in the absence of PhoQ or when a non-phosphorylatable PhoPD52A mutant is expressed. However, when PhoP transcriptional activation is achieved in a Mg2+- and PhoQ-independent manner, PhoP regains asymmetric polar localization. In addition, we show that, in the analyzed conditions, PhoQ cellular distribution does not parallel PhoP location pattern. These findings reveal that PhoP cellular location is dynamic and conditioned by its environmentally-defined transcriptional status, showing a new insight in the PhoP/PhoQ system mechanism.