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Blood, 23 July 2009, Vol. 114, No. 4, pp. 764-771. Prepublished online as a Blood First Edition Paper on April 20, 2009; DOI 10.1182/blood-2009-01-198309. This Article Full Text Full Text (PDF) All Versions of this Article: blood-2009-01-198309v1 114/4/764    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Rights and Permissions Citing Articles Citing Articles via CrossRef Google Scholar Articles by Nielsen, M. J. Articles by Moestrup, S. K. PubMed PubMed Citation Articles by Nielsen, M. J. Articles by Moestrup, S. K. Related Collections Red Cells, Iron, and Erythropoiesis Review Articles Social Bookmarking                   What's this?  Previous Article  |  Table of Contents  |  Next Article  REVIEW ARTICLE Receptor targeting of hemoglobin mediated by the haptoglobins: roles beyond heme scavenging Marianne Jensby Nielsen1, and Søren Kragh Moestrup1 1 Department of Medical Biochemistry, University of Aarhus, Aarhus, Denmark Haptoglobin, the haptoglobin-hemoglobin receptor CD163, and the heme oxygenase-1 are proteins with a well-established function in the clearance and metabolism of "free" hemoglobin released during intravascular hemolysis. This scavenging system counteracts the potentially harmful oxidative and NO-scavenging effects associated with "free" hemoglobin, and, furthermore, elicits an anti-inflammatory response. In the late primate evolution, haptoglobin variants with distinct functions have arisen, including haptoglobin polymers and the haptoglobin-related protein. The latter associates with a subspecies of high-density lipoprotein (HDL) particles playing a crucial role in the innate immunity against certain trypanosome parasites. Recent studies have elucidated this fairly sophisticated immune defense mechanism that takes advantage of a trypanosomal haptoglobin-hemoglobin receptor evolved to supply the parasite with heme. Because of the high resemblance between haptoglobin and haptoglobin-related protein, the receptor also takes up the complex of hemoglobin and the HDL-bound haptoglobin-related protein. This tricks the parasite into internalizing another HDL-associated protein and toxin, apolipoprotein L-I, that kills the parasite. In conclusion, variant human homologous hemoglobin-binding proteins that collectively may be designated the haptoglobins have diverted from the haptoglobin gene. On hemoglobin and receptor interaction, these haptoglobins contribute to different biologic events that go beyond simple removal from plasma of the toxic hemoglobin. CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

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