title: Nuclease A (Gbs0661), an extracellular nuclease of Streptococcus agalactiae, attacks the neutrophil extracellular traps and is needed for full virulence.
abstract: Most bacteria of the genus Streptococcus are opportunistic pathogens, and some of them produce extracellular DNases, which may be important for virulence. Genome analyses of Streptococcus agalactiae (GBS) neonate isolate NEM316 revealed the presence of seven genes putatively encoding secreted DNases, although their functions, if any, are unknown. In this study, we observed that respiration growth of GBS led to the extracellular accumulation of a putative nuclease, identified as being encoded by the gbs0661 gene. When overproduced in Lactococcus lactis, the protein was found to be a divalent cation-requiring, pH-stable and heat-stable nuclease that we named Nuclease A (NucA). Substitution of the histidine(148) by alanine reduced nuclease activity of the GBS wild-type strain, indicating that NucA is the major nuclease ex vivo. We determined that GBS is able to degrade the DNA matrix comprising the neutrophil extracellular trap (NET). The nucA(H148A) mutant was impaired for this function, implicating NucA in the virulence of GBS. In vivo infection studies confirmed that NucA is required for full infection, as the mutant strain allowed increased bacterial clearance from lung tissue and decreased mortality in infected mice. These results show that NucA is involved in NET escape and is needed for full virulence.
authors.affiliation: INRA, UMR1319 Micalis, F-78350, Jouy-en-Josas, France.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Derré-Bobillot
authors.forename: Naima G
authors.initials: NG
authors.lastname: Cortes-Perez
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Pascale
authors.initials: P
authors.lastname: Kharrat
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Couvé
authors.forename: Violette
authors.initials: V
authors.lastname: Da Cunha
authors.forename: Patrice
authors.initials: P
authors.lastname: Decker
authors.forename: Marie-Christophe
authors.initials: MC
authors.lastname: Boissier
authors.forename: Frédéric
authors.initials: F
authors.lastname: Escartin
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Cesselin
authors.forename: Philippe
authors.initials: P
authors.lastname: Langella
authors.forename: Luis G
authors.initials: LG
authors.lastname: Bermúdez-Humarán
authors.forename: Philippe
authors.initials: P
authors.lastname: Gaudu
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D057131:Immune Evasion; D008168:Lung / Q000382:microbiology; D051379:Mice; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000276:immunology* / Q000382:microbiology; D013290:Streptococcal Infections / Q000276:immunology* / Q000382:microbiology; D013292:Streptococcus agalactiae / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity*; D051217:Toll-Like Receptor 9 / Q000276:immunology; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9; D003851:Deoxyribonucleases