Journal of thrombosis and haemostasis : JTH, Jan 8, 2018
Many RAS family small GTPases are expressed in platelets, including RAC, RHOA, RAP, and H-/N-/RRA... more Many RAS family small GTPases are expressed in platelets, including RAC, RHOA, RAP, and H-/N-/RRAS1, but most of their signaling and cellular functions remain poorly understood. Like RRAS1, TC21/RRAS2 reverses HRAS-induced suppression of integrin activation in CHO cells. However, a role for TC21 in platelets has not been explored. To determine TC21 expression in platelets, TC21 activation in response to platelet agonists, and roles of TC21 in platelet function in vitro and in vivo thrombosis. We demonstrate that TC21 is expressed in human and murine platelets and is activated in response to agonists for the glycoprotein VI (GPVI)/FcRγ immunoreceptor tyrosine-based activation motif (ITAM)-containing collagen receptor, in a Src-dependent manner. GPVI-induced platelet aggregation, integrin α β activation, and α- and dense-granule secretion, as well as phosphorylation of Syk, PLCγ2, AKT, and ERK, were inhibited in TC21-deficient platelets ex vivo. In contrast, these responses were norma...
ADP-induced thromboxane generation depends on Src family kinases (SFKs) and is enhanced with pan-... more ADP-induced thromboxane generation depends on Src family kinases (SFKs) and is enhanced with pan-protein kinase C (PKC) inhibitors, but it is not clear how these two events are linked. The aim of the current study is to investigate the role of Y311 phosphorylated PKCδ in regulating ADP-induced platelet activation. In the current study, we employed various inhibitors and murine platelets from mice deficient in specific molecules to evaluate the role of PKCδ in ADP-induced platelet responses. We show that, upon stimulation of platelets with 2MeSADP, Y311 on PKCδ is phosphorylated in a P2Y1/Gq and Lyn-dependent manner. By using PKCδ and Lyn knockout murine platelets, we also show that tyrosine phosphorylated PKCδ plays a functional role in mediating 2MeSADP-induced thromboxane generation. 2MeSADP-induced PKCδ Y311 phosphorylation and thromboxane generation were potentiated in human platelets pre-treated with either a pan-PKC inhibitor, GF109203X or a PKC α/β inhibitor and in PKC α or β...
Journal of thrombosis and haemostasis : JTH, Jan 8, 2018
Many RAS family small GTPases are expressed in platelets, including RAC, RHOA, RAP, and H-/N-/RRA... more Many RAS family small GTPases are expressed in platelets, including RAC, RHOA, RAP, and H-/N-/RRAS1, but most of their signaling and cellular functions remain poorly understood. Like RRAS1, TC21/RRAS2 reverses HRAS-induced suppression of integrin activation in CHO cells. However, a role for TC21 in platelets has not been explored. To determine TC21 expression in platelets, TC21 activation in response to platelet agonists, and roles of TC21 in platelet function in vitro and in vivo thrombosis. We demonstrate that TC21 is expressed in human and murine platelets and is activated in response to agonists for the glycoprotein VI (GPVI)/FcRγ immunoreceptor tyrosine-based activation motif (ITAM)-containing collagen receptor, in a Src-dependent manner. GPVI-induced platelet aggregation, integrin α β activation, and α- and dense-granule secretion, as well as phosphorylation of Syk, PLCγ2, AKT, and ERK, were inhibited in TC21-deficient platelets ex vivo. In contrast, these responses were norma...
ADP-induced thromboxane generation depends on Src family kinases (SFKs) and is enhanced with pan-... more ADP-induced thromboxane generation depends on Src family kinases (SFKs) and is enhanced with pan-protein kinase C (PKC) inhibitors, but it is not clear how these two events are linked. The aim of the current study is to investigate the role of Y311 phosphorylated PKCδ in regulating ADP-induced platelet activation. In the current study, we employed various inhibitors and murine platelets from mice deficient in specific molecules to evaluate the role of PKCδ in ADP-induced platelet responses. We show that, upon stimulation of platelets with 2MeSADP, Y311 on PKCδ is phosphorylated in a P2Y1/Gq and Lyn-dependent manner. By using PKCδ and Lyn knockout murine platelets, we also show that tyrosine phosphorylated PKCδ plays a functional role in mediating 2MeSADP-induced thromboxane generation. 2MeSADP-induced PKCδ Y311 phosphorylation and thromboxane generation were potentiated in human platelets pre-treated with either a pan-PKC inhibitor, GF109203X or a PKC α/β inhibitor and in PKC α or β...
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Papers by S. Janapati