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Expression of platelet C1 inhibitor
A H Schmaier1, S Amenta, T Xiong
1Department of Internal Medicine, University of Michigan, Ann Arbor.
Blood
|July 15, 1993
Summary
Human platelets store C1 inhibitor (C1 INH), distinct from plasma. Activated platelets release and express C1 INH on their surface, potentially modulating inflammatory proteases.
Area of Science:
- Biochemistry
- Immunology
- Hematology
Background:
- Human platelets possess a unique intracellular reservoir of C1 inhibitor (C1 INH).
- Platelet C1 INH levels correlate with plasma C1 INH in healthy individuals and hereditary angioedema patients.
Purpose of the Study:
- To investigate the presence, release, and surface expression of C1 INH in human platelets.
- To explore the potential role of platelet C1 INH in modulating inflammatory responses.
Main Methods:
- Quantification of platelet C1 INH antigen using ELISA and immunoblots.
- Detection of C1 INH mRNA in megakaryocytes via RT-PCR.
- Analysis of C1 INH release and surface expression upon platelet activation.
Main Results:
- Platelets contain significantly higher C1 INH levels than C1 INH-deficient patients.
- C1 INH is a 105-Kd protein found in megakaryocytes and secreted/expressed by activated platelets.
- Activated platelets secrete 38% and express 23% of their total C1 INH.
Conclusions:
- Platelet C1 INH levels are influenced by megakaryocyte production and stored in alpha-granules.
- Secreted and membrane-expressed platelet C1 INH may regulate plasma protease activity in inflammation.