The Staphylococcus aureus lipoprotein SitC colocalizes with Toll-like receptor 2 (TLR2) in murine keratinocytes and elicits intracellular TLR2 accumulation.
SitC is one of the predominant lipoproteins in Staphylococcus aureus. Recently, SitC was shown to be capable of stimulating Toll-like receptor 2 (TLR2), but the mechanism of TLR2 activation by SitC has not been analyzed in detail so far. In this study, we purified C-terminally His-tagged SitC (SitC-His) from Staphylococcus aureus. SitC-His induced interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) release in human monocytes and also NF-κB activation in TLR2-transfected HEK293 cells, indicating TLR2-specific activation. SitC not only induced a TLR2-dependent release of IL-6 in primary murine keratinocytes (MKs) but also induced intracellular accumulation of TLR2, which was time and concentration dependent. Cy2-labeled SitC-His colocalized specifically with TLR2 in MKs and was also internalized in TLR2 knockout MKs, suggesting a TLR2-independent uptake. Neither activation nor colocalization of SitC-His was observed with TLR4 or Nod2. The results show that the native lipoprotein SitC-His specifically colocalizes with TLR2, is internalized by host cells, induces proinflammatory cytokines, and triggers intracellular accumulation of TLR2.
Müller
P
P
Department of Microbial Genetics, University of Tübingen, Tübingen, Germany.
Müller-Anstett
M
M
Wagener
J
J
Gao
Q
Q
Kaesler
S
S
Schaller
M
M
Biedermann
T
T
Götz
F
F
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism*; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053473:Nod2 Signaling Adaptor Protein / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D013047:Specific Pathogen-Free Organisms; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D016207:Cytokines; D008074:Lipoproteins; D053473:Nod2 Signaling Adaptor Protein; C495945:Nod2 protein, mouse; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2