Distinct role of PYK2 in mediating thromboxane generation downstream of both G12/13 and integrin αiibβ in platelets.
Proline-rich tyrosine kinase 2 (Pyk2) is activated by various agonists in platelets. We evaluated the signaling mechanism and the functional role of Pyk2 in platelets by using pharmacological inhibitors and Pyk2-deficient platelets. We found that platelet aggregation and secretion in response to 2-MeSADP and AYPGKF were diminished in the presence of Pyk2 inhibitors or in Pyk2-deficient platelets, suggesting that Pyk2 plays a positive regulatory role in platelet functional responses. It has been shown that ADP-, but not thrombin-, induced thromboxane (TxA2) generation depends on integrin signaling. Unlike ADP, thrombin activates G12/13 pathways, and G12/13 pathways can substitute for integrin signaling for TxA2 generation. We found that Pyk2 was activated downstream of both G12/13 and integrin-mediated pathways, and both 2-MeSADP- and AYPGKF-induced TxA2 generation was significantly diminished in Pyk2-deficient platelets. In addition, TxA2 generation induced by co-stimulation of Gi and Gz pathways, which is dependent on integrin signaling, was inhibited by blocking Pyk2. Furthermore, inhibition of 2-MeSADP-induced TxA2 generation by fibrinogen receptor antagonist was not rescued by co-stimulation of G12/13 pathways in the presence of Pyk2 inhibitor. We conclude that Pyk2 is a common signaling effector downstream of both G12/13 and integrin αIIbβ3 signaling which contributes to thromboxane generation.
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CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL GENE-Y GENE-Y GENE-N GENE-Y CHEMICAL GENE-Y GENE-N GENE-Y GENE-Y GENE-N GENE-Y GENE-Y GENE-Y GENE-Y GENE-Y CHEMICAL GENE-Y GENE-Y GENE-Y GENE-N GENE-Y GENE-N GENE-N GENE-N GENE-Y GENE-N CHEMICAL GENE-N GENE-Y GENE-N GENE-Y GENE-N GENE-Y CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL
ADP TxA2 2-MeSADP TxA2 TxA2 thromboxane Proline-rich tyrosine kinase 2 Gz integrin Pyk2 Proline fibrinogen receptor G12/13 Pyk2 Pyk2 G12/13 integrin αIIbβ3 Pyk2 Pyk2 Pyk2 Pyk2 2-MeSADP Pyk2 Pyk2 thrombin integrin thrombin G12/13 G12/13 integrin Pyk2 G12/13 TxA2 integrin Pyk2 Gi PYK2 G12/13 integrin αiibβ tyrosine thromboxane 2-MeSADP ADP thromboxane TxA2