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CD63 associates with the alphaIIb beta3 integrin-CD9 complex on the surface of activated platelets
S J Israels1, E M McMillan-Ward, J Easton
1Department of Pediatrics and the Manitoba Institute of Cell Biology, University of Manitoba, Winnipeg, Canada. israels@cc.umanitoba.ca
Thrombosis and Haemostasis
|February 24, 2001
Summary
Platelet activation by thrombin causes CD63 to associate with integrin alphaIIbbeta3 and tetraspanin CD9. This complex formation influences platelet interactions with neutrophils and aggregation.
Area of Science:
- Hematology
- Cell Biology
- Immunology
Background:
- Tetraspanins are integral membrane proteins found in multi-molecular complexes with integrins.
- CD63, a tetraspanin, translocates to the plasma membrane upon platelet activation.
- Integrin alphaIIbbeta3 plays a crucial role in platelet function.
Purpose of the Study:
- To investigate the role of CD63 in activated platelets.
- To determine the association of CD63 with other platelet proteins, including integrins and tetraspanins.
- To explore the functional consequences of CD63 complex formation.
Main Methods:
- Platelet activation using thrombin.
- Biochemical fractionation to isolate Triton-insoluble cytoskeletal components.
- Co-immunoprecipitation assays using anti-CD63 monoclonal antibody D545.
- Platelet adhesion and aggregation assays.
Main Results:
- Thrombin-induced platelet activation led to CD63 incorporation into the actin cytoskeleton, dependent on alphaIIbbeta3.
- CD63 was co-immunoprecipitated with alphaIIbbeta3 and CD9 in activated platelets.
- The anti-CD63 antibody D545 inhibited thrombin-activated platelet adhesion to neutrophils and ADP-induced disaggregation.
- D545 did not affect platelet adhesion to extracellular matrix proteins or aggregation induced by other agonists.
Conclusions:
- CD63 forms a complex with alphaIIbbeta3 and CD9 in activated platelets.
- This integrin-tetraspanin complex may modulate alphaIIbbeta3-dependent cell interactions, such as platelet-neutrophil adhesion.
- CD63 plays a role in specific platelet functions beyond simple aggregation.