Identification of a novel human MD-2 splice variant that negatively regulates Lipopolysaccharide-induced TLR4 signaling.
Myeloid differentiation factor 2 (MD-2) is a secreted gp that assembles with TLR4 to form a functional signaling receptor for bacterial LPS. In this study, we have identified a novel alternatively spliced isoform of human MD-2, termed MD-2 short (MD-2s), which lacks the region encoded by exon 2 of the MD-2 gene. Similar to MD-2, MD-2s is glycosylated and secreted. MD-2s also interacted with LPS and TLR4, but failed to mediate LPS-induced NF-kappaB activation and IL-8 production. We show that MD-2s is upregulated upon IFN-gamma, IL-6, and TLR4 stimulation and negatively regulates LPS-mediated TLR4 signaling. Furthermore, MD-2s competitively inhibited binding of MD-2 to TLR4. Our study pinpoints a mechanism that may be used to regulate TLR4 activation at the onset of signaling and identifies MD-2s as a potential therapeutic candidate to treat human diseases characterized by an overly exuberant or chronic immune response to LPS.
Gray
Pearl
P
Division of Pediatric Infectious Diseases and Immunology, Burns and Allen Research Institute, Cedars-Sinai Medical Center, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90048, USA.
Michelsen
Kathrin S
KS
Sirois
Cherilyn M
CM
Lowe
Emily
E
Shimada
Kenichi
K
Crother
Timothy R
TR
Chen
Shuang
S
Brikos
Constantinos
C
Bulut
Yonca
Y
Latz
Eicke
E
Underhill
David
D
Arditi
Moshe
M
D002460:Cell Line; D002469:Cell Separation; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D015870:Gene Expression; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D016209:Interleukin-8 / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000276:immunology*; D051218:Lymphocyte Antigen 96 / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D018613:Microscopy, Confocal; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000235:genetics* / Q000276:immunology / Q000378:metabolism
D016209:Interleukin-8; C495377:LY96 protein, human; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D020033:Protein Isoforms; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4