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.
Gastrointestinal Disease Area, Novartis Institutes for Biomedical Research, Horsham, United Kingdom.
Laurent-Herve
LH
Perez
Matt
M
Butler
Tammy
T
Creasey
JoAnn
J
Dzink-Fox
John
J
Gounarides
Stephanie
S
Petit
Anna
A
Ropenga
Neil
N
Ryder
Kathryn
K
Smith
Philip
P
Smith
Scott J
SJ
Parkinson
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