title: The histone deacetylase sirtuin 2 is a new player in the regulation of platelet function.
abstract: BACKGROUND
  Histone deacetylases (HDACs) play a key role in signaling in many cell types. However, little is known about the participation of HDACs, particularly sirtuins (SIRTs), in platelet reactivity.
  
  
  OBJECTIVE
  To investigate the role of HDACs in platelets, we examined the effects of SIRT inhibition on platelet function and protein acetylation in human platelets.
  
  
  METHODS
  We used washed platelets obtained from healthy subjects. Cambinol (SIRT1 and SIRT2 inhibitor), AGK2 (specific SIRT2 inhibitor) and EX527 (specific SIRT1 inhibitor) were used as SIRT inhibitors. Platelets were stimulated with collagen, thrombin, or U46619, and platelet responses were determined according to optical aggregometry findings, dense granule release, and cytosolic calcium levels (Fura-2AM fluorescence). Protein acetylation and phosphorylation were assessed by immunoblotting.
  
  
  RESULTS
  SIRT inhibition remarkably reduced platelet responses (aggregation, granule release, and cytosolic calcium level; P < 0.05). SIRT2 was present in platelets at the level of mRNA and protein, and its specific inhibition reduced platelet responses. The acetylated protein pattern observed in resting platelets changed during platelet aggregation. Inhibition of SIRT2 increased the acetylation of Akt kinase, which in turn blocked agonist-induced Akt phosphorylation and glycogen synthase kinase-3β phosphorylation, which are markers of Akt activity. Finally, collagen-induced aggregation provoked Akt acetylation.
  
  
  CONCLUSIONS
  Regulation of protein acetylation by SIRT2 plays a central role in platelet function. The effects of SIRT2 are mediated in part by the acetylation and inhibition of Akt. These results open a new avenue for research into the control of platelet function, and may help to identify new therapeutic targets.
authors.affiliation: Instituto Investigación Sanitaria Hospital La Fe, IIS La Fe, University Hospital La Fe, Valencia, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Moscardó
authors.affiliation: Instituto Investigación Sanitaria Hospital La Fe, IIS La Fe, University Hospital La Fe, Valencia, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Vallés
authors.affiliation: Instituto Investigación Sanitaria Hospital La Fe, IIS La Fe, University Hospital La Fe, Valencia, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Latorre
authors.affiliation: Experimental Hepatology Unit, IIS La Fe, CIBERehd, Valencia, Spain.|Department of Biochemistry and Molecular Biology, University of Valencia, Valencia, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Jover
authors.affiliation: Instituto Investigación Sanitaria Hospital La Fe, IIS La Fe, University Hospital La Fe, Valencia, Spain.
authors.forename: M T
authors.initials: MT
authors.lastname: Santos
mesh_terms: D000107:Acetylation; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D002118:Calcium / Q000097:blood; D003594:Cytoplasmic Granules / Q000201:enzymology / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000097:blood; D000071679:Glycogen Synthase Kinase 3 beta; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006801:Humans; D010766:Phosphorylation; D010974:Platelet Aggregation; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000097:blood; D012333:RNA, Messenger / Q000097:blood; D022142:Secretory Vesicles / Q000201:enzymology / Q000378:metabolism; D015398:Signal Transduction; D056565:Sirtuin 2 / Q000037:antagonists & inhibitors / Q000097:blood* / Q000235:genetics
chemical_list: D056572:Histone Deacetylase Inhibitors; D010975:Platelet Aggregation Inhibitors; D012333:RNA, Messenger; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; C474199:SIRT2 protein, human; D056565:Sirtuin 2; D002118:Calcium
keywords: Akt3 protein kinase; acetylation; blood platelet; signal transduction; sirtuins