Repository hosted by TU Delft Library

Home · Contact · About · Disclaimer ·
 

Degradation of tissue-type plasminogen activator by human monocyte- derived macrophages is mediated by the mannose receptor and by the low- density lipoprotein receptor-related protein

Publication files not online:

Author: Noorman, F. · Braat, E.A.M. · Rijken, D.C.
Type:article
Date:1995
Institution: TNO Preventie en Gezondheid
Source:Blood, 9, 86, 3421-3427
Identifier: 232914
Keywords: Biology · aminocaproic acid · lipopolysaccharide · low density lipoprotein receptor · mannose receptor · receptor protein · tissue plasminogen activator · article · controlled study · hemostasis · human · human cell · macrophage · molecular interaction · normal human · priority journal · protein degradation · receptor affinity · Cell Differentiation · Cells, Cultured · Dexamethasone · Human · LDL-Receptor Related Protein 1 · Lipopolysaccharides · Macrophages · Monocytes · Receptors, Cell Surface · Receptors, Immunologic · Support, Non-U.S. Gov't · Tissue Plasminogen Activator

Abstract

The balance of tissue-type plasminogen activator (t-PA) production and degradation determines its concentration in blood and tissues. Disturbance of this balance may result in either increased or decreased proteolysis. In the present study, we identified the receptor systems involved in the degradation of t-PA by human monocytes/macrophages in culture. Monocytes were cultured and became macrophages within 2 days. At 4°C, 125I-t-PA bound to macrophages with high (apparent dissociation constant [kd], 1 to 5 nmol/L) and low affinity (kd > 350 nmol/L). At 37°C, the cells internalized and degraded t-PA via the high affinity binding sites, which were partially inhibited by mannan. The low affinity binding sites were 6-aminohexanoic acid-inhibitable and not involved in t-PA degradation. Degradation of t-PA was upregulated during differentiation of monocytes to macrophages. Dexamethasone further upregulated the mannan-inhibitable t-PA degradation. Lipopolysaccharide downregulated both mannan-inhibitable and non-mannan- inhibitable t-PA degradation. Non-mannan-inhibitable degradation was completely blocked by recombinant 39-kD receptor-associated protein (RAP, inhibitor of lipoprotein receptor-related protein [LRP]), whereas mannan- inhibitable degradation was blocked by the addition of a monoclonal antibody against the mannose receptor. No differences between the degradation of t-PA and functionally inactivated t-PA were observed. We conclude that human monocyte-derived macrophages are able to bind, internalize, and degrade t- PA. Degradation of t-PA does not require complex formation with plasminogen activator inhibitors. The macrophages use two independently regulated receptors, namely, the mannose receptor and LRP, for the uptake and degradation of t-PA. Chemicals/CAS: aminocaproic acid, 1319-82-0, 60-32-2; tissue plasminogen activator, 105913-11-9; Dexamethasone, 50-02-2; LDL-Receptor Related Protein 1; Lipopolysaccharides; mannose receptor; Receptors, Cell Surface; Receptors, Immunologic; Tissue Plasminogen Activator, EC 3.4.21.68