A coding mutation within the first exon of the human MD-2 gene results in decreased lipopolysaccharide-induced signaling.
MD-2 is an accessory protein of the Toll-like receptor (TLR)-4, necessary for assembling a receptor complex to sense low quantities of lipopolysaccharide in order to subsequently trigger innate immune responses. MD-2 and TLR-4 are expressed on a variety of immunocompetent cells. Mutations within the TLR-4 gene have been shown to attenuate immune responses against lipopolysaccharide in mice. In humans, a TLR-4 polymorphism has been associated with a higher risk for developing severe Gram-negative sepsis and with a lower risk for atherosclerosis. Since MD-2 is an essential part of the lipopolysaccharide receptor complex, we screened 20 patients that underwent surgical cancer therapy for novel MD-2 mutations by a single-strand conformation polymorphism technique. In one patient we found an A --> G substitution at position 103, resulting in an amino-acid exchange from Thr 35 to Ala. Reporter gene assays revealed that this mutation resulted in a reduced lipopolysaccharide-induced signaling. The patient displayed an uneventful postoperative course, with the exception of slightly decreased TNF-alpha levels after in vitro stimulation with LPS as compared to wt patients. Genotyping of a further 41 patients by a newly developed Lightcycler/FRET method failed to detect any additional polymorphism carriers, indicating that this is a rare mutation.
Hamann
L
L
Institute for Microbiology and Hygiene, Charité Medical Center, Humboldt-University, Berlin, Germany. lutz.hamann@charite.de
Kumpf
O
O
Müller
M
M
Visintin
A
A
Eckert
J
J
Schlag
P M
PM
Schumann
R R
RR
D000409:Alanine / Q000235:genetics; D000954:Antigens, Surface / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008070:Lipopolysaccharides / Q000276:immunology* / Q000378:metabolism; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins / Q000378:metabolism; D009154:Mutation; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D013696:Temperature; D013912:Threonine / Q000235:genetics; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism
D000954:Antigens, Surface; C495377:LY96 protein, human; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D013912:Threonine; D000409:Alanine