title: Identification of a novel human MD-2 splice variant that negatively regulates Lipopolysaccharide-induced TLR4 signaling.
abstract: 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.
authors.affiliation: 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.
authors.forename: Pearl
authors.initials: P
authors.lastname: Gray
authors.forename: Kathrin S
authors.initials: KS
authors.lastname: Michelsen
authors.forename: Cherilyn M
authors.initials: CM
authors.lastname: Sirois
authors.forename: Emily
authors.initials: E
authors.lastname: Lowe
authors.forename: Kenichi
authors.initials: K
authors.lastname: Shimada
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Crother
authors.forename: Shuang
authors.initials: S
authors.lastname: Chen
authors.forename: Constantinos
authors.initials: C
authors.lastname: Brikos
authors.forename: Yonca
authors.initials: Y
authors.lastname: Bulut
authors.forename: Eicke
authors.initials: E
authors.lastname: Latz
authors.forename: David
authors.initials: D
authors.lastname: Underhill
authors.forename: Moshe
authors.initials: M
authors.lastname: Arditi
mesh_terms: 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
chemical_list: 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