Complementation between urokinase-producing and receptor-producing cells in extracellular matrix degradation

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biology

Background:

• Extracellular matrix (ECM) degradation is crucial for various physiological and pathological processes.
• Urokinase plasminogen activator (u-PA) and its receptor (u-PAR) are key regulators of ECM remodeling.
• The precise roles of u-PA and u-PAR in ECM degradation require further elucidation.

Purpose of the Study:

• To investigate the individual and combined roles of urokinase plasminogen activator (u-PA) and the u-PA receptor (u-PAR) in extracellular matrix degradation.
• To determine the necessity of cell-associated u-PAR for pro-u-PA activation and subsequent matrix degradation.

Main Methods:

• Expression of human pro-u-PA and human u-PAR in separate mouse LB6 cell lines.
• Cocultivation experiments to assess matrix degradation capacity.
• Immunoprecipitation to analyze pro-u-PA activation.
• Use of u-PA-receptor antagonists and solubilized u-PAR to probe binding requirements.

Main Results:

• Pro-u-PA-producing cells degraded matrix in the presence of plasminogen, but u-PAR-producing cells did not.
• Coculturing pro-u-PA and u-PAR producing cells increased matrix degradation rates at least threefold.
• Cocultivation enhanced the conversion of inactive pro-u-PA to active two-chain u-PA.
• Inhibition of pro-u-PA binding to u-PAR blocked both matrix degradation and pro-u-PA activation.
• Solubilized u-PAR did not enhance pro-u-PA activation, indicating the necessity of cell-associated receptors.

Conclusions:

• Cell-associated urokinase plasminogen activator receptor is essential for efficient activation of pro-u-PA.
• Binding of pro-u-PA to its receptor significantly enhances its catalytic activity, leading to increased extracellular matrix degradation.
• These findings suggest that cell-surface interactions involving u-PA and u-PAR are critical for in vivo proteolysis.