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Binding of tissue-type plasminogen activator by the mannose receptor

Author: Otter, M. · Barrett-Bergshoeff, M.M. · Rijken, D.C.
Type:article
Date:1991
Institution: Instituut voor Verouderings- en Vaatziekten Onderzoek TNO
Source:Journal of Biological Chemistry, 21, 266, 13931-13935
Identifier: 231589
Keywords: Biology · Animal · Cattle · Cell Membrane · Glucosaminidase · Ligands · Macrophages · Mannose · Pulmonary Alveoli · Receptors, Immunologic · Structure-Activity Relationship · Support, Non-U.S. Gov't · Tissue Plasminogen Activator · Animalia · Bos taurus · Bovinae

Abstract

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 M(r) 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.