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Bacitracin reveals a role for multiple thiol isomerases in platelet function
Aisling Robinson1, Sarah O'Neill, Aoife Kiernan
1Department of Clinical Pharmacology, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
British Journal of Haematology
|January 18, 2006
Summary
Platelet integrin alphaIIb beta3 possesses thiol isomerase activity crucial for its activation. Bacitracin, a thiol isomerase inhibitor, blocks platelet aggregation and secretion, revealing multiple isomerases regulate platelet function.
Area of Science:
- Biochemistry
- Hematology
- Molecular Biology
Background:
- Platelet-specific integrin alphaIIb beta3 contains endogenous thiol isomerase activity.
- This activity is linked to CXXC motifs in the beta subunit and plays a role in integrin activation.
Purpose of the Study:
- To provide further evidence for the functional significance of integrin thiol isomerase activity in integrin activation.
- To demonstrate the role of multiple thiol isomerases in overall platelet function.
Main Methods:
- Utilized purified bacitracin, a known thiol isomerase inhibitor.
- Assessed platelet aggregation induced by thrombin and collagen.
- Measured alphaIIb beta3 activation using PAC-1 binding and monitored platelet secretion (CD62P, CD63) and thromboxane A2 production.
Main Results:
- Bacitracin inhibited platelet aggregation and alphaIIb beta3 activation.
- Bacitracin demonstrated a 50% inhibitory concentration of 15.5 micromol/l against purified alphaIIb beta3 thiol isomerase activity.
- Bacitracin also inhibited integrin-independent platelet secretion and thromboxane production.
Conclusions:
- The endogenous thiol isomerase activity of alphaIIb beta3 is functionally significant for its activation.
- Multiple thiol isomerases, beyond alphaIIb beta3, play a role in regulating platelet function.
- These findings highlight a novel regulatory mechanism in platelet activation.