Identification of Novel Host Interactors of Effectors Secreted bySalmonellaandCitrobacter.
Many pathogenic bacteria of the familyEnterobacteriaceaeuse 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 theEnterobacteriaceaeintracellular pathogensSalmonella entericaserovar Typhimurium andCitrobacter rodentium. We identified 54 high-confidence host interactors for theSalmonellaeffectors GogA, GtgA, GtgE, SpvC, SrfH, SseL, SspH1, and SssB collectively and 21 interactors for theCitrobactereffectors EspT, NleA, NleG1, and NleK. We biochemically validated the interaction between the SrfHSalmonellaprotein 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.IMPORTANCEDuring 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 ofSalmonellaandCitrobactereffectors, which will help elucidate their mechanisms of action.
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA.
Ryan L
RL
Sontag
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA.
Ernesto S
ES
Nakayasu
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA.
Roslyn N
RN
Brown
Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon, USA.
George S
GS
Niemann
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA.
Michael A
MA
Sydor
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA.
Octavio
O
Sanchez
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA.
Charles
C
Ansong
Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, USA.
Shao-Yeh
SY
Lu
Saw Swee Hock School of Public Health, National University of Singapore, Singapore.
Hyungwon
H
Choi
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.
Dylan
D
Valleau
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA.
Karl K
KK
Weitz
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.
Alexei
A
Savchenko
Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon, USA.
Eric D
ED
Cambronne
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA.
Joshua N
JN
Adkins
affinity purification; effectors; mass spectrometry; pathogenic bacteria; protein-protein interactions; type III secretion system