Identification of Novel Host Interactors of Effectors Secreted by <italic toggle="yes">Salmonella</italic> and <italic toggle="yes">Citrobacter</italic>
Ryan L. Sontag,
Ernesto S. Nakayasu,
Roslyn N. Brown,
George S. Niemann,
Michael A. Sydor,
Octavio Sanchez,
Charles Ansong,
Shao-Yeh Lu,
Hyungwon Choi,
Dylan Valleau,
Karl K. Weitz,
Alexei Savchenko,
Eric D. Cambronne,
Joshua N. Adkins
Affiliations
Ryan L. Sontag
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA
Ernesto S. Nakayasu
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA
Roslyn N. Brown
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA
George S. Niemann
Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon, USA
Michael A. Sydor
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA
Octavio Sanchez
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA
Charles Ansong
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA
Shao-Yeh Lu
Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, USA
Hyungwon Choi
Saw Swee Hock School of Public Health, National University of Singapore, Singapore
Dylan Valleau
Department of Chemical Engineering and Applied Chemistry, Banting, and Best Department of Medical Research, Midwest Centre for Structural Genomics, University of Toronto, Toronto, Ontario, Canada
Karl K. Weitz
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA
Alexei Savchenko
Department of Chemical Engineering and Applied Chemistry, Banting, and Best Department of Medical Research, Midwest Centre for Structural Genomics, University of Toronto, Toronto, Ontario, Canada
Eric D. Cambronne
Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon, USA
Joshua N. Adkins
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA
ABSTRACT Many pathogenic bacteria of the family Enterobacteriaceae use type III secretion systems to inject virulence proteins, termed “effectors,” into the host cell cytosol. Although host-cellular activities of several effectors have been demonstrated, the function and host-targeted pathways of most of the effectors identified to date are largely undetermined. To gain insight into host proteins targeted by bacterial effectors, we performed coaffinity purification of host proteins from cell lysates using recombinant effectors from the Enterobacteriaceae intracellular pathogens Salmonella enterica serovar Typhimurium and Citrobacter rodentium. We identified 54 high-confidence host interactors for the Salmonella effectors GogA, GtgA, GtgE, SpvC, SrfH, SseL, SspH1, and SssB collectively and 21 interactors for the Citrobacter effectors EspT, NleA, NleG1, and NleK. We biochemically validated the interaction between the SrfH Salmonella protein and the extracellular signal-regulated kinase 2 (ERK2) host protein kinase, which revealed a role for this effector in regulating phosphorylation levels of this enzyme, which plays a central role in signal transduction. IMPORTANCE During infection, pathogenic bacteria face an adverse environment of factors driven by both cellular and humoral defense mechanisms. To help evade the immune response and ultimately proliferate inside the host, many bacteria evolved specialized secretion systems to deliver effector proteins directly into host cells. Translocated effector proteins function to subvert host defense mechanisms. Numerous pathogenic bacteria use a specialized secretion system called type III secretion to deliver effectors into the host cell cytosol. Here, we identified 75 new host targets of Salmonella and Citrobacter effectors, which will help elucidate their mechanisms of action.
