Leukocyte inflammatory responses provoked by pneumococcal sialidase.
Cell surface expression of sialic acid has been reported to decrease during immune cell activation, but the significance and regulation of this phenomenon are still being investigated. The major human bacterial pathogen Streptococcus pneumoniae causes pneumonia, sepsis and meningitis, often accompanied by strong inflammatory responses. S. pneumoniae expresses a sialidase (NanA) that contributes to mucosal colonization, platelet clearance, and blood-brain barrier penetration. Using wild-type and isogenic NanA-deficient mutant strains, we showed that S. pneumoniae NanA can desialylate the surface of human THP-1 monocytes, leading to increased ERK phosphorylation, NF-κB activation, and proinflammatory cytokine release. S. pneumoniae NanA expression also stimulates interleukin-8 release and extracellular trap formation from human neutrophils. A mechanistic contribution of unmasking of inhibitory Siglec-5 from cis sialic acid interactions to the proinflammatory effect of NanA is suggested by decreased SHP-2 recruitment to the Siglec-5 intracellular domain and RNA interference studies. Finally, NanA increased production of proinflammatory cytokines in a murine intranasal challenge model of S. pneumoniae pneumonia.
Department of Pediatrics, University of California, San Diego, La Jolla, California, USA.
Yung-Chi
YC
Chang
Satoshi
S
Uchiyama
Ajit
A
Varki
Victor
V
Nizet
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D006801:Humans; D016209:Interleukin-8 / Q000276:immunology; D007962:Leukocytes / Q000276:immunology*; D051379:Mice; D009439:Neuraminidase / Q000235:genetics / Q000276:immunology*; D011018:Pneumonia, Pneumococcal / Q000276:immunology* / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000201:enzymology* / Q000235:genetics / Q000276:immunology
D001426:Bacterial Proteins; D016209:Interleukin-8; D009439:Neuraminidase