Extracellular gelatinase of Enterococcus faecalis destroys a defense system in insect hemolymph and human serum.
We isolated Enterococcus faecalis from the body fluids of dead larvae of the greater wax moth, Galleria mellonella. Extracellular gelatinase (GelE) and serine protease (SprE), both of which are considered putative virulence factors of E. faecalis, were purified from the culture supernatant of E. faecalis. In an attempt to elucidate their virulence mechanisms, purified GelE and SprE were injected into hemolymph of G. mellonella and evaluated with regard to their effects on the immune system of insect hemolymph. As a result, it was determined that E. faecalis GelE degraded an inducible antimicrobial peptide (Gm cecropin) which is known to perform a critical role in host defense during the early phase of microbial infection. The results obtained from the G. mellonella-E. faecalis infection model compelled us to assess the virulence activity of GelE against the complement system in human serum. E. faecalis GelE hydrolyzed C3a and also mediated the degradation of the alpha chain of C3b, thereby inhibiting opsonization and the formation of the membrane attack complex resultant from the activation of the complement cascade triggered by C3 activation. In contrast, E. faecalis SprE exhibited no virulence effect against the immune system of insect hemolymph or human serum tested in this study.
Park
Shin Yong
SY
Department of Biotechnology, Hoseo University, 165 Sechuli, Baebangmyun, Asan City, Chungnam 336-795, South Korea.
Kim
Kyoung Mi
KM
Lee
Joon Ha
JH
Seo
Sook Jae
SJ
Lee
In Hee
IH
D000818:Animals; D001426:Bacterial Proteins / Q000502:physiology; D001483:Base Sequence; D015926:Complement C3a / Q000378:metabolism; D003179:Complement C3b / Q000378:metabolism; D015938:Complement Membrane Attack Complex / Q000037:antagonists & inhibitors; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004195:Disease Models, Animal; D013293:Enterococcus faecalis / Q000201:enzymology* / Q000276:immunology*; D018093:Gelatinases / Q000302:isolation & purification / Q000502:physiology*; D016908:Gram-Positive Bacterial Infections / Q000276:immunology; D006458:Hemolymph / Q000276:immunology* / Q000382:microbiology; D006801:Humans; D019476:Insect Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009036:Moths / Q000276:immunology* / Q000382:microbiology; D012697:Serine Endopeptidases / Q000302:isolation & purification / Q000502:physiology; D044967:Serum / Q000276:immunology* / Q000382:microbiology; D037521:Virulence Factors / Q000302:isolation & purification / Q000502:physiology*
D001426:Bacterial Proteins; D015938:Complement Membrane Attack Complex; D004269:DNA, Bacterial; D019476:Insect Proteins; D037521:Virulence Factors; D015926:Complement C3a; D003179:Complement C3b; D012697:Serine Endopeptidases; D018093:Gelatinases