Association of smooth muscle cell tissue factor with caveolae

There is still no satisfactory explanation for the low catalytic activity of tissue factor (TF)/factor VII(a) complexes towards coagulation factor X, as found on the apical surface side of cell layers. It has been hypothesized that TF exists in a latent form. Layers of cultured human smooth muscle c...

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Bibliographic Details
Published in:Blood 1996-08, Vol.88 (4), p.1306-1313
Main Authors: MULDER, A. B, SMIT, J. W, BOM, V. J. J, BLOM, N. R, RUITERS, M. H. J, HALIE, M. R, VAN DER MEER, J
Format: Article
Language:English
Subjects:
Biological and medical sciences
Blood Coagulation
Blood coagulation. Blood cells
Caveolin 1
Caveolins
Cell Adhesion
Cell Compartmentation
Cell Membrane - metabolism
Cell Membrane - ultrastructure
Cells, Cultured
Factor VIIa - metabolism
Factor Xa - metabolism
Fundamental and applied biological sciences. Psychology
General aspects, investigation methods, hemostasis, fibrinolysis
Humans
Membrane Glycoproteins - metabolism
Membrane Proteins - metabolism
Microscopy, Electron
Molecular and cellular biology
Muscle, Smooth, Vascular - metabolism
Thromboplastin - physiology
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Summary:There is still no satisfactory explanation for the low catalytic activity of tissue factor (TF)/factor VII(a) complexes towards coagulation factor X, as found on the apical surface side of cell layers. It has been hypothesized that TF exists in a latent form. Layers of cultured human smooth muscle cells, constitutively expressing TF, were immunogold-labeled for TF in situ and processed for electron microscopy. We showed that, besides internalization and accumulation in lysosomal-like structures, TF remained associated with noncoated, flask-shaped microinvaginations of the plasma membrane. These invaginations were identified as caveolae. In regions in which intercellular contacts were interrupted, more TF-positive caveolae were observed. Enzymatically detached smooth muscle cells exhibited a similar enlargement of caveolar structures. Concomitantly, an increase of catalytic activity of apically formed TF/VIIa complexes towards factor X was found on the suspended cells. We speculate that caveolae-associated TF may function as a latent pool of procoagulant activity, which can rapidly be activated at sites in which vessel wall integrity is lost.
ISSN:0006-4971
1528-0020
DOI:10.1182/blood.v88.4.1306.bloodjournal8841306