title: The macrophage mannose receptor promotes uptake of ADAMTS13 by dendritic cells.
abstract: ADAMTS13 is a plasma metalloproteinase that regulates platelet adhesion and aggregation by cleaving ultra-large VWF multimers on the surfaces of endothelial cells. Autoantibodies directed against ADAMTS13 prohibit the processing of VWF multimers, initiating a rare and life-threatening disorder called acquired thrombotic thrombocytopenic purpura. The formation of autoantibodies depends on the activation of CD4(+) T cells. This process requires immune recognition, endocytosis, and subsequent processing of ADAMTS13 into peptides that are presented on MHC class II molecules to CD4(+) T cells by dendritic cells (DCs). In the present study, we investigated endocytosis of recombinant ADAMTS13 by immature monocyte-derived DCs using flow cytometry and confocal microscopy. After incubation of fluorescently labeled ADAMTS13 with DCs, significant uptake of ADAMTS13 was observed. Endocytosis of ADAMTS13 was completely blocked by the addition of EGTA and mannan. ADAMTS13 endocytosis was decreased in the presence of a blocking mAb directed toward the macrophage mannose receptor (MR). Furthermore, siRNA silencing of MR reduced the uptake of ADAMTS13 by DCs. In addition, in vitro binding studies confirmed the interaction of ADAMTS13 with the carbohydrate recognition domains of MR. The results of the present study indicate that sugar moieties on ADAMTS13 interact with MR, thereby promoting its endocytosis by APCs.
authors.affiliation: Department of Plasma Proteins, Sanquin-Academic Medical Center Landsteiner Laboratory, Amsterdam, The Netherlands.
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Sorvillo
authors.forename: Wouter
authors.initials: W
authors.lastname: Pos
authors.forename: Linda M
authors.initials: LM
authors.lastname: van den Berg
authors.forename: Rob
authors.initials: R
authors.lastname: Fijnheer
authors.forename: Luisa
authors.initials: L
authors.lastname: Martinez-Pomares
authors.forename: Teunis B
authors.initials: TB
authors.lastname: Geijtenbeek
authors.forename: Eszter
authors.initials: E
authors.lastname: Herczenik
authors.forename: Jan
authors.initials: J
authors.lastname: Voorberg
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000493:pharmacokinetics*; D000071120:ADAMTS13 Protein; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism*; D004705:Endocytosis / Q000276:immunology*; D005434:Flow Cytometry; D020868:Gene Silencing; D006801:Humans; D037181:Lectins, C-Type / Q000378:metabolism*; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000378:metabolism*; D018613:Microscopy, Confocal; D009000:Monocytes / Q000276:immunology / Q000378:metabolism*; D011485:Protein Binding / Q000276:immunology; D011956:Receptors, Cell Surface / Q000378:metabolism*
chemical_list: D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D011956:Receptors, Cell Surface; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human