title: Membrane-anchored CD14 is required for LPS-induced TLR4 endocytosis in TLR4/MD-2/CD14 overexpressing CHO cells.
abstract: Lipopolysaccharide (LPS) induces inflammatory activation through TLR4 (toll-like receptor-4)/MD-2 (myeloid differentiation-2)/CD14 (cluster of differentiation-14) complex. Although optimal LPS signaling is required to activate our innate immune systems against gram-negative bacterium, excessive amount of LPS signaling develops a detrimental inflammatory response in gram-negative bacterial infections. Downregulation of surface TLR4 expression is one of the critical mechanisms that can restrict LPS signaling. Here, we found that membrane-anchored CD14 is required for LPS-induced downregulation of TLR4 and MD-2 in CHO cells. Moreover, pretreatment of the cells with sterol-binding agent filipin reduced LPS-induced TLR4 downregulation, suggesting the involvement of caveolae-mediated endocytosis pathway. Involvement of caveolae in LPS-induced TLR4 endocytosis was further confirmed by immunoprecipitation. Thus, our data indicate that caveolae-dependent endocytosis pathway is involved in LPS-induced TLR4 downregulation and that this is dependent on membrane-anchored CD14 expression.
authors.affiliation: Department of Molecular Medicine, Kumamoto University, Kumamoto 862-0973, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Shuto
authors.forename: Kosuke
authors.initials: K
authors.lastname: Kato
authors.forename: Yoko
authors.initials: Y
authors.lastname: Mori
authors.forename: Suganya
authors.initials: S
authors.lastname: Viriyakosol
authors.forename: Mariko
authors.initials: M
authors.lastname: Oba
authors.forename: Takashi
authors.initials: T
authors.lastname: Furuta
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Okiyoneda
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Arima
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Suico
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Kai
mesh_terms: D000818:Animals; D016466:CHO Cells; D022461:Caveolins / Q000378:metabolism; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D006224:Cricetinae; D015536:Down-Regulation / Q000187:drug effects; D004705:Endocytosis / Q000187:drug effects*; D005786:Gene Expression Regulation; D018950:Lipopolysaccharide Receptors / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051218:Lymphocyte Antigen 96 / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
chemical_list: D022461:Caveolins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D051197:Toll-Like Receptor 4