title: Identification of the haemoglobin scavenger receptor.
abstract: Intravascular haemolysis is a physiological phenomenon as well as a severe pathological complication when accelerated in various autoimmune, infectious (such as malaria) and inherited (such as sickle cell disease) disorders. Haemoglobin released into plasma is captured by the acute phase protein haptoglobin, which is depleted from plasma during elevated haemolysis. Here we report the identification of the acute phase-regulated and signal-inducing macrophage protein, CD163, as a receptor that scavenges haemoglobin by mediating endocytosis of haptoglobin-haemoglobin complexes. CD163 binds only haptoglobin and haemoglobin in complex, which indicates the exposure of a receptor-binding neoepitope. The receptor-ligand interaction is Ca2+-dependent and of high affinity. Complexes of haemoglobin and multimeric haptoglobin (the 2-2 phenotype) exhibit higher functional affinity for CD 163 than do complexes of haemoglobin and dimeric haptoglobin (the 1-1 phenotype). Specific CD163-mediated endocytosis of haptoglobin-haemoglobin complexes is measurable in cells transfected with CD163 complementary DNA and in CD163-expressing myelo-monocytic lymphoma cells.
authors.affiliation: Department of Medical Biochemistry, University of Aarhus, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Kristiansen
authors.forename: J H
authors.initials: JH
authors.lastname: Graversen
authors.forename: C
authors.initials: C
authors.lastname: Jacobsen
authors.forename: O
authors.initials: O
authors.lastname: Sonne
authors.forename: H J
authors.initials: HJ
authors.lastname: Hoffman
authors.forename: S K
authors.initials: SK
authors.lastname: Law
authors.forename: S K
authors.initials: SK
authors.lastname: Moestrup
mesh_terms: D000818:Animals; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016466:CHO Cells; D006224:Cricetinae; D004705:Endocytosis; D004912:Erythrocytes / Q000378:metabolism; D006242:Haptoglobins / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D014162:Transfection; D000098902:CD163 Antigen
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000098902:CD163 Antigen; D006242:Haptoglobins; D006454:Hemoglobins; D011956:Receptors, Cell Surface; C027079:hemoglobin-haptoglobin receptor; D006419:Heme Oxygenase (Decyclizing)