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Competition between plasminogen and tissue plasminogen activator for cellular binding sites
J Felez1, C J Chanquia, P Fabregas
1Institut De Recerca Oncologica, Hospital Duran i Reynals, Autovia de Castelldefels, L'Hospitalet de Llobregat, Barcelona, Spain.
Blood
|October 15, 1993
Summary
Cellular receptors for tissue plasminogen activator (t-PA) and plasminogen share common binding sites on cells. This interaction influences cell-associated proteolytic activity and plasminogen activation.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Biology
Background:
- Cellular receptors regulate plasminogen activation and proteolytic activity.
- Interactions of plasminogen and tissue plasminogen activator (t-PA) with monocytes show similarities.
- Previous studies suggest potential shared binding sites.
Purpose of the Study:
- To directly determine if t-PA and plasminogen share common binding sites on cells.
- To investigate the implications of shared binding sites on cellular proteolytic activity.
Main Methods:
- Competitive binding assays using radiolabeled ligands (125I-plasminogen and 125I-rt-PA).
- Testing on nine different cell types (adherent and suspension).
- Analysis of receptor expression modulation and interaction with candidate receptor molecules (gangliosides, alpha-enolase).
Main Results:
- Recombinant human single-chain t-PA (rt-PA) inhibited 125I-plasminogen binding, and vice versa.
- This reciprocal inhibition was observed across nine cell types.
- Plasminogen and t-PA receptor expression were modulated in parallel under various conditions.
- Candidate plasminogen receptor molecules also interacted with t-PA.
Conclusions:
- At least a component of the binding sites for plasminogen is shared with t-PA.
- Shared receptor occupancy by plasminogen and/or t-PA can modulate cellular proteolytic activity.
- These findings provide insight into the regulation of cell-associated fibrinolysis.