SpvC is a Salmonella effector with phosphothreonine lyase activity on host mitogen‐activated protein kinases

Piotr Mazurkiewicz,Jessica A Thompson,David W Holden,Jerry Thomas,Philippe Sansonetti,Mei Liu,Laurence Arbibe

doi:10.1111/j.1365-2958.2008.06134.x

Piotr Mazurkiewicz, Jessica A Thompson + Show 5 more

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https://doi.org/10.1111/j.1365-2958.2008.06134.x

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Abstract

SpvC is encoded by the Salmonella virulence plasmid. We have investigated the biochemical function of SpvC and the mechanism by which it is secreted by bacteria and translocated into infected macrophages. We constructed a strain carrying a deletion in spvC and showed that the strain is attenuated for systemic virulence in mice. SpvC can be secreted in vitro by either the SPI-1 or SPI-2 type III secretion systems. Cell biological and genetic experiments showed that translocation of the protein into the cytosol of macrophages by intracellular bacteria is dependent on the SPI-2 T3SS. Using antibodies specific to phospho-amino acids and mass spectrometry we demonstrate that SpvC has phosphothreonine lyase activity on full-length phospho-Erk (pErk) and a synthetic 13-amino-acid phospho-peptide containing the TXY motif. A Salmonella strain expressing spvC from a plasmid downregulated cytokine release from infected cells.

Highlights

We have investigated the biochemical function of SpvC and the mechanism by which it is secreted by bacteria and translocated into infected macrophages
Cell biological and genetic experiments showed that translocation of the protein into the cytosol of macrophages by intracellular bacteria is dependent on the SPI-2 T3SS
Using antibodies specific to phospho-amino acids and mass spectrometry we demonstrate that SpvC has phosphothreonine lyase activity on full-length phospho-Erk and a synthetic 13-amino-acid phospho-peptide containing the TXY motif

Summary

Introduction

The T3SS encoded within Salmonella pathogenicity island 1 (SPI-1) is produced by extracellular bacteria and delivers effectors across the host cell plasma membrane; these are necessary for bacterial internalization and the early stages of Salmonella-containing vacuole (SCV) formation (Zhou and Galan, 2001; Schlumberger and Hardt, 2006). The SPI-2-encoded T3SS is activated by internalized Salmonella and translocates effectors across the vacuolar membrane. These support bacterial replication in epithelial cells and macrophages, interfere with MHC class II presentation (Mitchell et al, 2004) and induce macrophage motility (Worley et al, 2006) and cytotoxicity (Rytkonen et al, 2007). SPI-2 T3SS effectors are required for systemic virulence in the murine model of salmonellosis (Shea et al, 1996; Waterman and Holden, 2003)

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