Yersinia virulence factor YopM induces sustained RSK activation by interfering with dephosphorylation.
BACKGROUND
Pathogenic yersiniae inject several effector proteins (Yops) into host cells, which subverts immune functions and enables the bacteria to survive within the host organism. YopM, whose deletion in enteropathogenic yersiniae results in a dramatic loss of virulence, has previously been shown to form a complex with and activate the multifunctional kinases PKN2 and RSK1 in transfected cells.


RESULTS
In a near physiological approach with double-affinity-tagged YopM being translocated into the macrophage cell line J774A.1 via the natural type three secretion system of Yersinia we verified the interaction of YopM with PKN2 and RSK1 and detected association with additional PKN and RSK isoforms. In transfected and infected cells YopM induced sustained phosphorylation of RSK at its activation sites serine-380 and serine-221 even in the absence of signalling from its upstream kinase ERK1/2, suggesting inhibition of dephosphorylation. ATP-depletion and in vitro assays using purified components directly confirmed that YopM shields RSK isoforms from phosphatase activity towards serines 380 and 221.


CONCLUSIONS
Our study suggests that during Yersinia infection YopM induces sustained activation of RSK by blocking dephosphorylation of its activatory phosphorylation sites. This may represent a novel mode of action of a bacterial virulence factor.
Institute of Medical Microbiology, Virology and Hygiene, University Medical Center Eppendorf, Hamburg, Germany. jbaltzer@mta.ca
Moritz
M
Hentschke
Laura
L
Berneking
Cristina
C
Belmar Campos
Friedrich
F
Buck
Klaus
K
Ruckdeschel
Martin
M
Aepfelbacher
D000595:Amino Acid Sequence; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D002846:Chromatography, Affinity; D017931:DNA Primers; D004789:Enzyme Activation; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism*; D015398:Signal Transduction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D015007:Yersinia / Q000472:pathogenicity*
D001425:Bacterial Outer Membrane Proteins; D017931:DNA Primers; C060772:yopM protein, Yersinia; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C512964:Rps6ka1 protein, mouse