title: Phospholipid flippases attenuate LPS-induced TLR4 signaling by mediating endocytic retrieval of Toll-like receptor 4.
abstract: P4-ATPases are lipid flippases that catalyze the transport of phospholipids to create membrane phospholipid asymmetry and to initiate the biogenesis of transport vesicles. Here we show, for the first time, that lipid flippases are essential to dampen the inflammatory response and to mediate the endotoxin-induced endocytic retrieval of Toll-like receptor 4 (TLR4) in human macrophages. Depletion of CDC50A, the β-subunit that is crucial for the activity of multiple P4-ATPases, resulted in endotoxin-induced hypersecretion of proinflammatory cytokines, enhanced MAP kinase signaling and constitutive NF-κB activation. In addition, CDC50A-depleted THP-1 macrophages displayed reduced tolerance to endotoxin. Moreover, endotoxin-induced internalization of TLR4 was strongly reduced and coincided with impaired endosomal MyD88-independent signaling. The phenotype of CDC50A-depleted cells was also induced by separate knockdown of two P4-ATPases, namely ATP8B1 and ATP11A. We conclude that lipid flippases are novel elements of the innate immune response that are essential to attenuate the inflammatory response, possibly by mediating endotoxin-induced internalization of TLR4.
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
authors.forename: Vincent A
authors.initials: VA
authors.lastname: van der Mark
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Ghiboub
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
authors.forename: Casper
authors.initials: C
authors.lastname: Marsman
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
authors.forename: Remco
authors.initials: R
authors.lastname: van Dijk
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
authors.forename: Johan K
authors.initials: JK
authors.lastname: Hiralall
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
authors.forename: Kam S
authors.initials: KS
authors.lastname: Ho-Mok
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
authors.forename: Zoë
authors.initials: Z
authors.lastname: Castricum
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
authors.forename: Wouter J
authors.initials: WJ
authors.lastname: de Jonge
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
authors.forename: Ronald P J
authors.initials: RP
authors.lastname: Oude Elferink
authors.affiliation: Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands. c.c.paulusma@amc.uva.nl.
authors.forename: Coen C
authors.initials: CC
authors.lastname: Paulusma
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000276:immunology*; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D004705:Endocytosis; D055785:Gene Knockdown Techniques; D006801:Humans; D007113:Immunity, Innate; D008070:Lipopolysaccharides / Q000276:immunology*; D008264:Macrophages / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology; D053594:Myeloid Differentiation Factor 88 / Q000276:immunology; D016328:NF-kappa B / Q000276:immunology; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000276:immunology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; C495345:TLR4 protein, human; C526978:TMEM30a protein, human; D051197:Toll-Like Receptor 4; D000251:Adenosine Triphosphatases; C111067:ATP8B1 protein, human; C548142:ATP11A protein, human
keywords: ATP8B1; Endocytosis; Innate immunity; Macrophage; P4-ATPase; Phospholipid flippase