Binding of tissue-type plasminogen activator by the mannose receptor.
Previous studies have shown that tissue-type plasminogen activator (t-PA) in blood is cleared by the liver partially through a mannose-specific uptake system. The present study was undertaken to investigate, in a purified system, whether t-PA is recognized by the mannose receptor which is expressed on macrophages and liver sinusoidal cells. The mannose receptor was isolated and purified from bovine alveolar macrophages and migrated as a single protein band at Mr 175,000 on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Ligand blotting revealed that this protein specifically bound t-PA. The t-PA-receptor interaction was further characterized in a binding assay, which showed saturable binding with an apparent dissociation constant of 1 nM. t-PA binding required calcium ions and was negligible in the presence of EDTA or at acid pH. Mannose-albumin was an effective inhibitor, whereas galactose-albumin did not have a significant effect. From a series of monosaccharides tested, D-mannose and L-fucose were the most potent inhibitors, N-acetyl-D-glucosamine was a moderate inhibitor, whereas D-galactose and N-acetyl-D-galactosamine were ineffective. t-PA, deglycosylated by endoglycosidase H, did not interact with the receptor. It is concluded that the mannose receptor specifically binds t-PA, probably through its high mannose-type oligosaccharide.
Otter
M
M
Gaubius Institute TNO, Leiden, The Netherlands.
Barrett-Bergshoeff
M M
MM
Rijken
D C
DC
D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D006596:Hexosaminidases / Q000494:pharmacology; D037181:Lectins, C-Type; D008024:Ligands; D008264:Macrophages / Q000378:metabolism; D008358:Mannose / Q000378:metabolism; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D011650:Pulmonary Alveoli / Q000378:metabolism; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic / Q000302:isolation & purification / Q000378:metabolism*; D013329:Structure-Activity Relationship; D010959:Tissue Plasminogen Activator / Q000737:chemistry / Q000378:metabolism*
D037181:Lectins, C-Type; D008024:Ligands; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D006596:Hexosaminidases; D010959:Tissue Plasminogen Activator; D008358:Mannose