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Serotonin secretion from human platelets may be modified by Ca2+-activated, phospholipid-dependent myosin
The Journal of Biological Chemistry
|December 10, 1984
Summary
The protein kinase C inhibitor H-7 enhanced serotonin release in human platelets by blocking the phosphorylation of a key myosin light chain. This suggests a role for myosin light-chain phosphorylation in regulating platelet secretion.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Platelet activation involves serotonin release and protein phosphorylation.
- Protein kinase C (PKC) is implicated in cellular signaling pathways.
- Myosin light chain 20 (LC20) phosphorylation is linked to platelet function.
Purpose of the Study:
- To investigate the role of protein kinase C (PKC) in serotonin release from human platelets.
- To determine the effect of the PKC inhibitor H-7 on platelet protein phosphorylation and serotonin secretion.
Main Methods:
- Utilized 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine (H-7) as a selective protein kinase C inhibitor.
- Measured serotonin release and radioactive phosphate incorporation into platelet proteins.
- Employed two-dimensional peptide mapping after tryptic hydrolysis to analyze protein phosphorylation patterns.
Main Results:
- H-7 enhanced serotonin release induced by 12-O-tetradecanoyl phorbol 13-acetate (TPA).
- H-7 decreased phosphate incorporation into a 20,000-dalton protein (LC20) without affecting unstimulated platelets.
- Peptide mapping confirmed H-7 selectively inhibited PKC-catalyzed phosphorylation of myosin light chain.
Conclusions:
- PKC-mediated phosphorylation of myosin light chain (LC20) may inhibit serotonin release in human platelets.
- Ca2+-activated, phospholipid-dependent myosin light-chain phosphorylation plays a regulatory role in platelet secretion.