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Localization and translocation of MMP-2 during aggregation of human platelets
G Sawicki1, E J Sanders, E Salas
1Department of Pharmacology, University of Alberta, Edmonton, Canada.
Abstract:
We have previously shown that human platelets express matrix metalloproteinase-2 (MMP-2) and that the release of this enzyme during platelet activation mediates the ADP- and thromboxane-independent part of aggregation. We have now used immunogold electron microscopy, flow cytometry. Western blot analysis and zymography methods to study the ultrastructural localization of MMP-2 in human washed platelets. Platelet aggregation was stimulated by collagen and the MMP-2 immunoreactivity of platelets was followed during various stages of aggregation. In resting platelets, MMP-2 was randomly distributed in the platelet cytosol without detectable association with platelet granules. Platelet aggregation caused the translocation of MMP-2 from the cytosol to the extracellular space. During the early stages of aggregation, MMP-2 remained in close association with the platelet plasma membrane. We conclude that the interactions of MMP-2 with platelet surface membranes mediate the aggregatory response induced by this enzyme.
Insights
Human platelets release matrix metalloproteinase-2 (MMP-2) during activation, which is crucial for aggregation. This enzyme interacts with platelet surface membranes, mediating the aggregation response.
Area of Science:
- Hematology
- Biochemistry
- Cell Biology
Background:
- Human platelets express matrix metalloproteinase-2 (MMP-2).
- MMP-2 release during platelet activation mediates ADP- and thromboxane-independent aggregation.
Purpose of the Study:
- To investigate the ultrastructural localization of MMP-2 in human platelets.
- To understand the role of MMP-2 translocation during platelet aggregation.
Main Methods:
- Immunogold electron microscopy
- Flow cytometry
- Western blot analysis
- Zymography
- Collagen-stimulated platelet aggregation
Main Results:
- In resting platelets, MMP-2 is randomly distributed in the cytosol.
- Platelet aggregation induces MMP-2 translocation from the cytosol to the extracellular space.
- During early aggregation, MMP-2 associates with the platelet plasma membrane.
Conclusions:
- MMP-2 translocation and its interaction with platelet surface membranes are key mechanisms in collagen-induced platelet aggregation.