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Comparison of Phorbol Ester-induced Responses in Rabbit and Human Platelets and Difference in Shape Change.
1Pharmacological Institute, College of Medicine, National Taiwan University, No. 1, Jen-Ai Rd, 1st Section, Taipei, 10018, Taiwan, 886-2-322-1742.
Platelets
|November 4, 2010
Summary
Phorbol 12,13-dibutyrate (PDBu) triggers platelet aggregation and shape change, involving protein phosphorylation but not calcium flux or phosphoinositide breakdown. Protein kinase C inhibition blocks these PDBu-induced platelet responses.
Area of Science:
- Platelet biology
- Cell signaling
- Biochemistry
Background:
- Platelets play a crucial role in hemostasis and thrombosis.
- Protein kinase C (PKC) is implicated in various cellular processes, including platelet activation.
Purpose of the Study:
- To investigate the effects of Phorbol 12,13-dibutyrate (PDBu) on human and rabbit platelets.
- To elucidate the signaling pathways involved in PDBu-induced platelet responses.
Main Methods:
- Platelet aggregation and ATP release assays.
- Measurement of intracellular calcium ([Ca(2+)](f)) and thromboxane B2 (TxB(2)) formation.
- Protein phosphorylation analysis (20K and 47K proteins).
- Inhibition studies using staurosporine (PKC inhibitor), EGTA, and other agents.
Main Results:
- PDBu induced concentration-dependent platelet aggregation and ATP release in human and rabbit platelets.
- PDBu caused platelet shape change and phosphorylation of 20K and 47K proteins in rabbit platelets.
- PDBu did not induce phosphoinositide breakdown, increase [Ca(2+)](f), or form TxB(2).
- Staurosporine blocked all PDBu-induced responses, while EGTA and verapamil inhibited aggregation.
Conclusions:
- PDBu-induced platelet aggregation and shape change are mediated by protein kinase C.
- The mechanism involves protein phosphorylation, likely of the 20K myosin light chain, rather than calcium mobilization or phosphoinositide hydrolysis.
