Analyzing the mechanism of Rap1 activation in platelets: Rap1 activation is related to the release reaction mediated through the collagen receptor GPVI

Jung, Stéphanie; Ohnuma, Mio; Watanabe, Naohide; Sonoda, Mamiko; Handa, Makoto; Moroi, Masaaki

doi:10.1016/j.thromres.2005.11.002

Cited by 11 publications

(7 citation statements)

References 27 publications

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“…Consistently, piceatannol blocked convulxin-induced aggregation but not that induced by thrombin (data not shown). PI3K activity has also been shown to be an important element of the signaling cascades proximal to GPVI but not PAR receptors (33). Two different PI3K inhibitors, wortmannin and LY294002, blocked the loss of Arf6-GTP in response to convulxin stimulation, but not in response to thrombin (Fig.…”

Section: Activation-dependent Loss Of Arf6-gtp In Platelets-inmentioning

confidence: 92%

Primary Platelet Signaling Cascades and Integrin-mediated Signaling Control ADP-ribosylation Factor (Arf) 6-GTP Levels during Platelet Activation and Aggregation

Karim

Choi

Whiteheart

2008

Journal of Biological Chemistry

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Previous studies showed that ADP-ribosylation factor 6 (Arf6) is important for platelet function; however, little is known about which signaling events regulate this small GTP-binding protein. Arf6-GTP was monitored in platelets stimulated with a number of agonists (TRAP, thrombin, convulxin, collagen, PMA, thapsigargin, or A23187) and all led to a time-dependent decrease in Arf6-GTP. ADP and U46619 were without effect. Using inhibitors, it was shown that the decrease of Arf6-GTP is a direct consequence of known signaling cascades. Upon stimulation via PAR receptors, Arf6-GTP loss could be blocked by treatment with U-73122, BAPTA/AM, Ro-31-8220, or Gö6976, indicating requirements for phospholipase C, calcium, and protein kinase C (PKC) ␣/␤, respectively. The Arf6-GTP decrease in convulxin-stimulated platelets showed similar requirements and was also sensitive to piceatannol, wortmannin, and LY294002, indicating additional requirements for Syk and phosphatidylinositol 3-kinase. The convulxin-induced decrease was sensitive to both PKC␣/␤ and ␦ inhibitors. Outside-in signaling, potentially via integrin engagement, caused a second wave of signaling that affected Arf6. Inclusion of RGDS peptides or EGTA, during activation, led to a biphasic response; Arf6-GTP levels partially recovered upon continued incubation. A similar response was seen in ␤3 integrin-null platelets. These data show that Arf6-GTP decreases in response to known signaling pathways associated with PAR and GPVI. They further reveal a second, aggregation-dependent, process that dampens Arf6-GTP recovery. This study demonstrates that the nucleotide state of Arf6 in platelets is regulated during the initial phases of activation and during the later stages of aggregation.

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Section: Activation-dependent Loss Of Arf6-gtp In Platelets-inmentioning

confidence: 92%

Primary Platelet Signaling Cascades and Integrin-mediated Signaling Control ADP-ribosylation Factor (Arf) 6-GTP Levels during Platelet Activation and Aggregation

Karim

Choi

Whiteheart

2008

Journal of Biological Chemistry

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“…Concentrations of inhibitors were used that are maximally effective. These concentrations were identified in previous studies from the Watson group and others [27–30]. The generation of mice disrupted in the genes encoding α IIb () or PLCγ2 (PLCγ2 –/– ) was as described [24,31].…”

Section: Methodsmentioning

confidence: 99%

Distinct but critical roles for integrin α_IIbβ₃ in platelet lamellipodia formation on fibrinogen, collagen‐related peptide and thrombin

et al. 2006

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Platelets play an essential role in the formation of a haemostatic plug at the site of vascular injury. This process requires adhesion of the platelet to the exposed subendothelial matrix, followed by powerful intracellular signalling events that lead to plateletplatelet interactions and thrombus formation. One critical feature in this scheme is the dramatic alteration in platelet morphology in response to activation. Thus, the resting, discoid platelet undergoes a series of morphological changes that include rounding, generation of filopodia and lamellipodia, and formation of actin stress fibres [1]. These events serve to stabilize the thrombus, thereby enabling it to withstand the high shear forces found in arteries and arterioles.Stable adhesion of platelets to the subendothelial matrix is dependent upon sustained activation of integrins [2]. Integrins are glycoprotein heterodimers Integrins are the major receptor type known to facilitate cell adhesion and lamellipodia formation on extracellular matrix proteins. However, collagenrelated peptide and thrombin have recently been shown to mediate platelet lamellipodia formation when presented as immobilized surfaces. The aims of this study were to establish if there exists a role for the platelet integrin a IIb b 3 in this response; and if so, whether signalling from the integrin is required for lamellipodia formation on these surfaces. Real-time analysis was used to compare platelet morphological changes on surfaces of fibrinogen, collagen-related peptide or thrombin in the presence of various pharmacological inhibitors and platelets from 'knockout' mice. We demonstrate that collagen-related peptide and thrombin stimulate distinct patterns of platelet lamellipodia formation and elevation of intracellular Ca 2+ to that induced by the integrin a IIb b 3 ligand, fibrinogen. Nevertheless, lamellipodia formation on collagen-related peptide and thrombin is dependent upon engagement of a IIb b 3 , consistent with release of a IIb b 3 ligand(s) from platelet granules. However, the requirement for signalling by the integrin on fibrinogen can be bypassed by the addition of thrombin to the solution. These observations reveal a critical role for a IIb b 3 in forming lamellipodia on collagen-related peptide and thrombin which is dependent on its ability to function as an adhesive receptor but not necessarily on its ability to signal. These results suggest that integrins may play an important role in lamellipodia formation triggered by nonintegrin ligands in platelets and possibly in other cell types.Abbreviations CRP, collagen-related peptide.

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“…Activation of P2Y 1 signals phospholipase β, leading to DAG formation, calcium mobilization, and eventually PKC and CalDAG-GEF activation. 1 In contrast, P2Y 12 activation inhibits adenylyl cyclase, activates phosphoinositide 3-kinase,2 the small GTPase Rap1,3 and activation of αIIbβ3 4…”

Section: P2y Receptor Antagonistsmentioning

confidence: 99%

Newer agents in antiplatelet therapy: a review

Yeung¹,

Holinstat²

2012

JBM

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Antiplatelet therapy remains the mainstay in preventing aberrant platelet activation in pathophysiological conditions such as myocardial infarction, ischemia, and stroke. Although there has been significant advancement in antiplatelet therapeutic approaches, aspirin still remains the gold standard treatment in the clinical setting. Limitations in safety, efficacy, and tolerability have precluded many of the antiplatelet inhibitors from use in patients. Unforeseen incidences of increased bleeding risk and recurrent arterial thrombosis observed in patients have hampered the development of superior next generation antiplatelet therapies. The pharmacokinetic and pharmacodynamic profiles have also limited the effectiveness of a number of antiplatelet inhibitors currently in use due to variability in metabolism, time to onset, and reversibility. A focused effort in the development of newer antiplatelet therapies to address some of these shortcomings has resulted in a significant number of potential antiplatelet drugs which target enzymes (phosphodiesterase, cyclooxygenase), receptors (purinergic, prostaglandins, protease-activated receptors, thromboxane), and glycoproteins (αIIbβ3, GPVI, vWF, GPIb) in the platelet. The validation and search for newer antiplatelet therapeutic approaches proven to be superior to aspirin is still ongoing and should yield a better pharmacodynamic profile with fewer untoward side-effects to what is currently in use today.

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Analyzing the mechanism of Rap1 activation in platelets: Rap1 activation is related to the release reaction mediated through the collagen receptor GPVI

Cited by 11 publications

References 27 publications

Primary Platelet Signaling Cascades and Integrin-mediated Signaling Control ADP-ribosylation Factor (Arf) 6-GTP Levels during Platelet Activation and Aggregation

Primary Platelet Signaling Cascades and Integrin-mediated Signaling Control ADP-ribosylation Factor (Arf) 6-GTP Levels during Platelet Activation and Aggregation

Distinct but critical roles for integrin α_IIbβ₃ in platelet lamellipodia formation on fibrinogen, collagen‐related peptide and thrombin

Newer agents in antiplatelet therapy: a review

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Analyzing the mechanism of Rap1 activation in platelets: Rap1 activation is related to the release reaction mediated through the collagen receptor GPVI

Cited by 11 publications

References 27 publications

Primary Platelet Signaling Cascades and Integrin-mediated Signaling Control ADP-ribosylation Factor (Arf) 6-GTP Levels during Platelet Activation and Aggregation

Primary Platelet Signaling Cascades and Integrin-mediated Signaling Control ADP-ribosylation Factor (Arf) 6-GTP Levels during Platelet Activation and Aggregation

Distinct but critical roles for integrin αIIbβ3 in platelet lamellipodia formation on fibrinogen, collagen‐related peptide and thrombin

Newer agents in antiplatelet therapy: a review

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Distinct but critical roles for integrin α_IIbβ₃ in platelet lamellipodia formation on fibrinogen, collagen‐related peptide and thrombin