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Association of smooth muscle cell tissue factor with caveolae
A B Mulder1, J W Smit, V J Bom
1Department of Haematology, University Hospital, University of Groningen, The Netherlands.
Blood
|August 15, 1996
Summary
Tissue factor (TF) associates with caveolae, acting as a latent procoagulant pool. Disruption of cell contacts releases TF, increasing its catalytic activity for factor X.
Area of Science:
- Cell Biology
- Biochemistry
- Hematology
Background:
- The low catalytic activity of tissue factor (TF)/factor VII(a) complexes on cell apical surfaces is poorly understood.
- TF is hypothesized to exist in a latent form, influencing coagulation.
- Investigating TF localization and function in smooth muscle cells is crucial for understanding hemostasis.
Purpose of the Study:
- To investigate the subcellular localization of tissue factor (TF) in cultured human smooth muscle cells.
- To explore the relationship between TF localization and its catalytic activity towards coagulation factor X.
- To elucidate the role of caveolae in regulating TF procoagulant activity.
Main Methods:
- Immunogold labeling of TF in situ in cultured human smooth muscle cells.
- Electron microscopy to visualize TF localization within cellular structures.
- Enzymatic detachment of cells to assess changes in TF activity.
Main Results:
- TF was found associated with flask-shaped plasma membrane microinvaginations, identified as caveolae.
- Increased TF-positive caveolae were observed in regions with interrupted intercellular contacts.
- Detached smooth muscle cells showed enlarged caveolae and increased catalytic activity of apical TF/VIIa complexes.
Conclusions:
- Caveolae may serve as a reservoir for latent tissue factor (TF) procoagulant activity.
- Disruption of cell-cell contacts and vessel wall integrity can release TF from caveolae.
- This mechanism allows for rapid activation of TF at sites of vascular injury.