Direct bacterial killing in vitro by recombinant Nod2 is compromised by Crohn's disease-associated mutations.
BACKGROUND
A homeostatic relationship with the intestinal microflora is increasingly appreciated as essential for human health and wellbeing. Mutations in the leucine-rich repeat (LRR) domain of Nod2, a bacterial recognition protein, are associated with development of the inflammatory bowel disorder, Crohn's disease. We investigated the molecular mechanisms underlying disruption of intestinal symbiosis in patients carrying Nod2 mutations.


RESULTS
In this study, using purified recombinant LRR domains, we demonstrate that Nod2 is a direct antimicrobial agent and this activity is generally deficient in proteins carrying Crohn's-associated mutations. Wild-type, but not Crohn's-associated, Nod2 LRR domains directly interacted with bacteria in vitro, altered their metabolism and disrupted the integrity of the plasma membrane. Antibiotic activity was also expressed by the LRR domains of Nod1 and other pattern recognition receptors suggesting that the LRR domain is a conserved anti-microbial motif supporting innate cellular immunity.


CONCLUSIONS
The lack of anti-bacterial activity demonstrated with Crohn's-associated Nod2 mutations in vitro, supports the hypothesis that a deficiency in direct bacterial killing contributes to the association of Nod2 polymorphisms with the disease.
Perez
Laurent-Herve
LH
Gastrointestinal Disease Area, Novartis Institutes for Biomedical Research, Horsham, United Kingdom.
Butler
Matt
M
Creasey
Tammy
T
Dzink-Fox
JoAnn
J
Gounarides
John
J
Petit
Stephanie
S
Ropenga
Anna
A
Ryder
Neil
N
Smith
Kathryn
K
Smith
Philip
P
Parkinson
Scott J
SJ
D001419:Bacteria / Q000187:drug effects*; D003424:Crohn Disease / Q000235:genetics* / Q000382:microbiology; D006801:Humans; D009154:Mutation; D053473:Nod2 Signaling Adaptor Protein / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000494:pharmacology
C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein; D011994:Recombinant Proteins