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Urokinase receptors in human monocytes
A Nykjaer1, C M Petersen, E I Christensen
1Institute of Physiology, University of Aarhus, Denmark.
Biochimica Et Biophysica Acta
|May 22, 1990
Summary
Human monocytes possess urokinase receptors with high affinity. During culture, these monocytes develop into macrophage-like cells, increasing receptor capacity but decreasing affinity.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Monocytes differentiate into macrophages, undergoing significant functional changes.
- Urokinase plasminogen activator (uPA) plays a role in cell migration and tissue remodeling.
- Understanding uPA receptor dynamics is crucial for inflammatory and cancer research.
Purpose of the Study:
- To characterize urokinase receptors on human monocytes and their changes during differentiation.
- To investigate the affinity, capacity, and localization of uPA receptors.
- To determine the fate of bound urokinase upon receptor interaction.
Main Methods:
- Isolation and culture of human monocytes.
- Binding assays using radiolabeled urokinase at different temperatures.
- Affinity cross-linking to identify receptor complexes.
- Electron microscopic autoradiography for receptor localization.
Main Results:
- Fresh monocytes exhibit high-affinity urokinase receptors (55 pM at 4°C).
- Monocyte-to-macrophage differentiation increases receptor binding capacity 5-7 fold with decreased affinity (500 pM at 4°C).
- Receptors are located on the plasma membrane, particularly in microvilli-rich areas, with minimal ligand internalization.
Conclusions:
- Human monocytes possess high-affinity urokinase receptors.
- Differentiation into macrophage-like cells leads to increased receptor numbers and reduced affinity.
- Urokinase receptors are primarily membrane-bound with limited degradation of the bound ligand.