Background: Acetylation of non-histone proteins is an emerging mechanism of signal transduction in nucleated cells. The best-established function for cytoplasmic acetylation is regulation of microtubule stability by a-tubulin acetylation, a process controlled by the action of histone deacetylases (HDACs) HDAC6 and sirt2. However, the role of acetylation of proteins in anucleated platelets is relatively unknown.

Aims: Our goal was to study: (1) the presence of acetylated proteins in human platelets, (2) the regulation of a-tubulin acetylation by aspirin and HDACs, and (3) the effect of a-tubulin acetylation on platelet reactivity.

Methods: Washed human platelets were treated with inhibitors previously to activation with indicated agonists.

Results: We found that in resting platelets, several proteins are acetylated, including a-tubulin. Aspirin treatment or inhibition of HDACs with trichostatin A (TSA) 15 µmol/L, but not inhibition of sirt2, strongly increased α-tubulin acetylation, suggesting that HDAC6 could be responsible for α-tubulin deacetylation. Immunoblotting experiments demonstrated the presence of HDAC6 in platelet lysates, and the agonist-dependent incorporation of HDAC6 into the reorganized cytoskeleton together with acetylated α-tubulin. Platelet aggregation induced α-tubulin deacetylation, a process inhibited by blocking the α_IIbβ₃ receptor. TSA-induced acetylation of α-tubulin was associated with reduced platelet aggregation, dense granule release, and calcium increase in response to collagen and U46619. To confirm the implication of HDAC6 in these processes, we used Tubastatin A, an specific inhibitor of HDAC6, and found that incubation with this agent increased α-tubulin acetylation and inhibited platelet aggregation.

Conclusions: These results indicated that aspirin and HDAC6 regulate the acetylation/deacetylation of α-tubulin a process strikingly related to platelet responses.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/acetylation-of-%ce%b1-tubulin-by-aspirin-and-histone-deacetylase-6-in-human-platelets/