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Ca2+ influx mediated through the GPIIb/IIIa complex during platelet activation
A Yamaguchi1, N Yamamoto, H Kitagawa
1Department of Cardiovascular Research, Tokyo Metropolitan Institute of Medical Science, Japan.
FEBS Letters
|December 10, 1987
Summary
Platelet activation involves calcium influx and mobilization. The glycoprotein IIb/IIIa complex is crucial for calcium influx during thrombin and collagen activation, impacting platelet aggregation.
Area of Science:
- Biochemistry
- Cell Biology
- Hematology
Background:
- Platelets play a critical role in hemostasis and thrombosis.
- Intracellular calcium ([Ca2+]i) signaling is a key regulator of platelet function.
- The glycoprotein IIb/IIIa (GPIIb/IIIa) complex is essential for platelet aggregation.
Purpose of the Study:
- To investigate the role of the GPIIb/IIIa complex in calcium dynamics during platelet activation.
- To differentiate the sources of intracellular calcium ([Ca2+]i) during platelet stimulation.
Main Methods:
- Aequorin luminescence was used to measure intracellular calcium ([Ca2+]i) levels in platelets.
- Platelets were stimulated with thrombin, collagen, and PMA.
- Monoclonal antibody TM83 and GRGDSP peptide were used to inhibit GPIIb/IIIa complex function.
Main Results:
- Aequorin luminescence showed two peaks upon thrombin stimulation, reflecting both external calcium influx and internal calcium release.
- External calcium influx contributed to one-half of the first peak and the entire second peak.
- Inhibition of the GPIIb/IIIa complex abolished the second peak of calcium influx.
- Similar effects on calcium influx were observed with collagen activation but not PMA activation.
Conclusions:
- The GPIIb/IIIa complex is directly involved in mediating a portion of the calcium influx during platelet activation by thrombin and collagen.
- These findings highlight the intricate relationship between GPIIb/IIIa-mediated signaling and calcium homeostasis in platelets.