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Thiols in the alphaIIbbeta3 integrin are necessary for platelet aggregation
Nagaraj Manickam1, Xiuhua Sun, Kevin W Hakala
1Department of Medicine Division of Hematology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
British Journal of Haematology
|June 10, 2008
Summary
p-chloromercuribenzene sulphonate (pCMBS) targets specific platelet thiols, revealing a non-P2Y(12) pathway crucial for alphaIIbbeta3 integrin activation and platelet aggregation.
Area of Science:
- Biochemistry
- Hematology
- Molecular Biology
Background:
- Platelet aggregation is vital for hemostasis and thrombosis.
- Sulfhydryl groups on platelet surface proteins play a key role in aggregation.
- The specific thiol-proteins targeted by p-chloromercuribenzene sulphonate (pCMBS) remain largely undefined.
Purpose of the Study:
- To identify specific thiol-proteins involved in platelet aggregation.
- To investigate the role of thiol groups in alphaIIbbeta3 integrin activation.
- To elucidate the mechanism of pCMBS inhibition of platelet aggregation.
Main Methods:
- Utilized ADP scavenger apyrase and P2Y(12) antagonist 2-MeSAMP to isolate non-P2Y(12) pathways.
- Employed 3-(N-maleimidylpropionyl)biocytin (MPB) and pCMBS for thiol labeling of platelet proteins.
- Confirmed thiol labeling specificity using mass spectrometry and 5,5'-dithiobis-(2-nitrobenzoic acid) inhibition.
Main Results:
- Identified a non-P2Y(12) thiol-dependent reaction in late-stage, alphaIIbbeta3-dependent aggregation.
- pCMBS preferentially reacted with thiols in the alphaIIbbeta3 integrin, unlike MPB.
- pCMBS inhibited platelet aggregation and signaling-independent alphaIIbbeta3 activation by Mn(2+).
Conclusions:
- Specific thiols within the alphaIIbbeta3 integrin are critical for its activation.
- pCMBS effectively inhibits platelet aggregation by targeting these alphaIIbbeta3 thiols.
- This study defines a novel pCMBS-sensitive pathway in platelet activation.
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