The ESX-5 System of Pathogenic Mycobacteria Is Involved In Capsule Integrity and Virulence through Its Substrate PPE10.
Mycobacteria produce a capsule layer, which consists of glycan-like polysaccharides and a number of specific proteins. In this study, we show that, in slow-growing mycobacteria, the type VII secretion system ESX-5 plays a major role in the integrity and stability of the capsule. We have identified PPE10 as the ESX-5 substrate responsible for this effect. Mutants in esx-5 and ppe10 both have impaired capsule integrity as well as reduced surface hydrophobicity. Electron microscopy, immunoblot and flow cytometry analyses demonstrated reduced amounts of surface localized proteins and glycolipids, and morphological differences in the capsular layer. Since capsular proteins secreted by the ESX-1 system are important virulence factors, we tested the effect of the mutations that cause capsular defects on virulence mechanisms. Both esx-5 and ppe10 mutants of Mycobacterium marinum were shown to be impaired in ESX-1-dependent hemolysis. In agreement with this, the ppe10 and esx5 mutants showed reduced recruitment of ubiquitin in early macrophage infection and intermediate attenuation in zebrafish embryos. These results provide a pivotal role for the ESX-5 secretion system and its substrate PPE10, in the capsular integrity of pathogenic mycobacteria. These findings open up new roads for research on the mycobacterial capsule and its role in virulence and immune modulation.
Department of Medical Microbiology and Infection Prevention, VU University Medical Center, Amsterdam, the Netherlands.
Louis S
LS
Ates
Department of Medical Microbiology and Infection Prevention, VU University Medical Center, Amsterdam, the Netherlands.|Department of Molecular Microbiology, VU University, Amsterdam, the Netherlands.
Aniek D
AD
van der Woude
Department of Medical Microbiology and Infection Prevention, VU University Medical Center, Amsterdam, the Netherlands.
Jovanka
J
Bestebroer
Department of Molecular Microbiology, VU University, Amsterdam, the Netherlands.
Gunny
G
van Stempvoort
Department of Physiology and Cardiology, VU University Medical Center, Amsterdam, the Netherlands.
René J P
RJ
Musters
Department of Molecular Cell Biology and Immunology, VU University Medical Center, Amsterdam, the Netherlands.
Juan J
JJ
Garcia-Vallejo
Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Amsterdam the Netherlands.
Daisy I
DI
Picavet
Department of Medical Microbiology and Infection Prevention, VU University Medical Center, Amsterdam, the Netherlands.
Robert van de
Rv
Weerd
Eyen SE, Prague, Czech Republic.
Massimiliano
M
Maletta
Department of Medical Microbiology and Infection Prevention, VU University Medical Center, Amsterdam, the Netherlands.
Coenraad P
CP
Kuijl
Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Amsterdam the Netherlands.
Nicole N
NN
van der Wel
Department of Medical Microbiology and Infection Prevention, VU University Medical Center, Amsterdam, the Netherlands.|Department of Molecular Microbiology, VU University, Amsterdam, the Netherlands.
Wilbert
W
Bitter
D000818:Animals; D016667:Bacterial Capsules / Q000378:metabolism*; D002460:Cell Line; D002855:Chromatography, Thin Layer; D004195:Disease Models, Animal; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D008854:Microscopy, Electron; D009165:Mycobacterium Infections, Nontuberculous / Q000378:metabolism*; D019910:Mycobacterium marinum / Q000378:metabolism / Q000472:pathogenicity*; D000069377:Type VII Secretion Systems / Q000378:metabolism*; D014774:Virulence / Q000502:physiology*; D037521:Virulence Factors / Q000378:metabolism; D015027:Zebrafish
D000069377:Type VII Secretion Systems; D037521:Virulence Factors