title: Role of phosphoinositide 3-kinase beta in platelet aggregation and thromboxane A2 generation mediated by Gi signalling pathways.
abstract: PI3Ks (phosphoinositide 3-kinases) play a critical role in platelet functional responses. PI3Ks are activated upon P2Y12 receptor stimulation and generate pro-aggregatory signals. P2Y12 receptor has been shown to play a key role in the platelet aggregation and thromboxane A2 generation caused by co-stimulation with Gq or Gz, or super-stimulation of Gi pathways. In the present study, we evaluated the role of specific PI3K isoforms alpha, beta, gamma and delta in platelet aggregation, thromboxane A2 generation and ERK (extracellular-signal-regulated kinase) activation. Our results show that loss of the PI3K signal impaired the ability of ADP to induce platelet aggregation, ERK phosphorylation and thromboxane A2 generation. We also show that Gq plus Gi- or Gi plus Gz-mediated platelet aggregation, ERK phosphorylation and thromboxane A2 generation in human platelets was inhibited by TGX-221, a PI3Kbeta-selective inhibitor, but not by PIK75 (a PI3Kalpha inhibitor), AS252424 (a PI3Kgamma inhibitor) or IC87114 (a PI3Kdelta inhibitor). TGX-221 also showed a similar inhibitory effect on the Gi plus Gz-mediated platelet responses in platelets from P2Y1-/- mice. Finally, 2MeSADP (2-methyl-thio-ADP)-induced Akt phosphorylation was significantly inhibited in the presence of TGX-221, suggesting a critical role for PI3Kbeta in Gi-mediated signalling. Taken together, our results demonstrate that PI3Kbeta plays an important role in ADP-induced platelet aggregation. Moreover, PI3Kbeta mediates ADP-induced thromboxane A2 generation by regulating ERK phosphorylation.
authors.affiliation: Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
authors.forename: Analia
authors.initials: A
authors.lastname: Garcia
authors.forename: Soochong
authors.initials: S
authors.lastname: Kim
authors.forename: Kamala
authors.initials: K
authors.lastname: Bhavaraju
authors.forename: Simone M
authors.initials: SM
authors.lastname: Schoenwaelder
authors.forename: Satya P
authors.initials: SP
authors.lastname: Kunapuli
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000097:blood; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D018345:Mice, Knockout; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000097:blood*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011744:Pyrimidinones / Q000494:pharmacology; D018048:Receptors, Purinergic P2 / Q000172:deficiency / Q000235:genetics; D058472:Receptors, Purinergic P2Y1; D015398:Signal Transduction / Q000187:drug effects; D013928:Thromboxane A2 / Q000097:blood*
chemical_list: D000244:Adenosine Diphosphate; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D007527:Isoenzymes; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D011744:Pyrimidinones; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D013928:Thromboxane A2; C546382:P2RY1 protein, human; C546383:P2ry1 protein, mouse; C504718:TGX 221