title: Annexin A2 tetramer activates human and murine macrophages through TLR4.
abstract: Annexins are a large family of intracellular phospholipid-binding proteins, yet several extracellular roles have been identified. Specifically, annexin A2, found in a heterotetrameric complex with S100A10, not only serves as a key extracellular binding partner for pathogens and host proteins alike, but also can be shed or secreted. We reported previously that soluble annexin A2 tetramer (A2t) activates human monocyte-derived macrophages (MDM), resulting in secretion of inflammatory mediators and enhanced phagocytosis. Although a receptor for A2t has been cloned from bone marrow stromal cells, data contained in this study demonstrate that it is dispensable for A2t-dependent activation of MDM. Furthermore, A2t activates wild-type murine bone marrow-derived macrophages, whereas macrophages from myeloid differentiation factor 88-deficient mice display a blunted response, suggesting a role for Toll-like receptor (TLR) signaling. Small interfering RNA knockdown of TLR4 in human MDM reduced the response to A2t, blocking antibodies against TLR4 (but not TLR2) blocked activation altogether, and bone marrow-derived macrophages from TLR4(-/-) mice were refractory to A2t. These data demonstrate that the modulation of macrophage function by A2t is mediated through TLR4, suggesting a previously unknown, but important role for this stress-sensitive protein in the detection of danger to the host, whether from injury or invasion.
authors: Laboratory of Molecular and Developmental Immunology, Division of Monoclonal Antibodies, Office of Biotechnology Products, Center for Drug Evaluation and Research, Food and Drug Administration, Bethesda, MD, USA.
authors: Jennifer F A
authors: JF
authors: Swisher
authors: Nicholas
authors: N
authors: Burton
authors: Silvia M
authors: SM
authors: Bacot
authors: Stefanie N
authors: SN
authors: Vogel
authors: Gerald M
authors: GM
authors: Feldman
mesh_terms: D000818:Animals; D017306:Annexin A2 / Q000378:metabolism / Q000502:physiology*; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000378:metabolism; D008262:Macrophage Activation / Q000187:drug effects / Q000235:genetics* / Q000276:immunology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D055503:Protein Multimerization / Q000502:physiology; D034741:RNA, Small Interfering / Q000494:pharmacology; D017154:Stromal Cells / Q000187:drug effects / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D017306:Annexin A2; D053594:Myeloid Differentiation Factor 88; D034741:RNA, Small Interfering; D051197:Toll-Like Receptor 4