Convulxin-induced platelet aggregation is accompanied by a powerful activation of the phospholipase C pathway

Faili, Ahmad; Randon, Jacques; Francischetti, Ivo M.B.; Vargäftig, B. Boris; Hatmi, Mohamed

doi:10.1042/bj2980087

Cited by 27 publications

(10 citation statements)

References 28 publications

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“…The absence of shape change when these amplification loops were blocked could be due to the fact that collagen stimulation of the FcγR/PLCγ2 pathway was not able to induce a sufficiently strong signal. The non‐physiologic agonists convulxin and CRP (collagen‐related peptide) are known to trigger a marked clustering of GPVI, which results in strong platelet activation (data not shown) [25,37,47–49]. Convulxin and CRP, unlike collagen, also cause platelet shape change despite treatment of the cells with aspirin and MRS2179 [27] and data not shown.…”

Section: Discussionmentioning

confidence: 99%

The P2Y1receptor plays an essential role in the platelet shape change induced by collagen when TxA2 formation is prevented

Mangin

Ohlmann

Eckly

et al. 2004

Journal of Thrombosis and Haemostasis

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To cite this article: Mangin P, Ohlmann P, Eckly A, Cazenave J-P, Lanza F, Gachet C. The P2Y 1 receptor plays an essential role in the platelet shape change induced by collagen when TxA2 formation is prevented. J Thromb Haemost 2004; 2: 969-77.Summary. ADP and TxA2 are secondary agonists which play an important role as cofactors when platelets are activated by agonists such as collagen or thrombin. The aim of the present study was to characterize the role of the ADP receptor P2Y 1 in collagen-induced activation of washed platelets. Inhibition of P2Y 1 alone with the selective antagonist MRS2179 prolonged the lag phase preceding aggregation in response to low or high concentrations of fibrillar collagen, without affecting the maximum amplitude of aggregation or secretion. A combination of MRS2179 and aspirin resulted in complete inhibition of platelet shape change at low and high collagen concentrations, together with a profound decrease in aggregation and secretion. Scanning electron microscopy showed that these platelets had conserved the discoid morphology typical of the resting state. A lack of shape change was also observed in aspirin-treated P2Y 1 -and G aq -deficient mouse platelets and in d-storage pooldeficient platelets from Fawn Hooded rats. In contrast, when the second ADP receptor P2Y 12 was inhibited with AR-C69931MX, aspirin-treated platelets were still able to change shape and displayed only a moderate decrease in aggregation and secretion. In conclusion, this study provides evidence that collagen requires not only the TxA2 receptor Tpa, but also P2Y 1 , to induce platelet shape change.

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Section: Discussionmentioning

confidence: 99%

The P2Y1receptor plays an essential role in the platelet shape change induced by collagen when TxA2 formation is prevented

Mangin

Ohlmann

Eckly

et al. 2004

Journal of Thrombosis and Haemostasis

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“…Cvx is a potent inducer of platelet activation [5]and binds with high affinity to rabbit [4]and human [6]platelets. Cvx activates PLC [7]by a mechanism that is not blocked by the cyclooxygenase inhibitor aspirin, by the PAF antagonist WEB 2086, and/or by the ADP scavenger enzymatic system CP/CPK, indicating that PLC activation is independent of the secondary agonist produced by activated platelets [5, 7]. Cvx‐induced PLC activation is, however, blocked by inhibitors acting on the protein tyrosine kinases, genistein and staurosporine [8].…”

Section: Introductionmentioning

confidence: 99%

Phosphatidylinositol 3′‐kinase and tyrosine‐phosphatase activation positively modulate Convulxin‐induced platelet activation. Comparison with collagen

et al. 1999

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In this report we have studied the role of phosphatidylinositol 3P-kinase (PI3-K) and tyrosine phosphatase activation on platelet activation by Convulxin (Cvx). Wortmannin, a specific PI3-K inhibitor, and phenylarsine oxide (PAO), a sulfhydryl reagent that inhibits tyrosine phosphatase (PTPase), block Cvx-induced platelet aggregation, granule secretion, inositol phosphate production, and increase in [Ca P+ ] i . However, PAO does not inhibit Cvx-induced tyrosine phosphorylation of platelet proteins, including Syk and PLCQ Q2, but blocked collagen-induced platelet aggregation as well as tyrosine phosphorylation of PLCQ Q2. In contrast, Cvx-induced PLCQ Q2 tyrosyl phosphorylation was partially inhibited by wortmannin. We conclude that (i) although Cvx and collagen activate platelets by a similar mechanism, different regulatory processes are specific to each agonist; (ii) mechanisms other than tyrosine phosphorylation regulate PLCQ Q2 activity; and (iii) besides protein tyrosine kinases, PI3-K (and PTPase) positively modulate platelet activation by both Cvx and collagen, and this enzyme is required for effective transmission of GPVI-Fc receptor Q Q chain signal to result in full activation and tyrosine phosphorylation of PLCQ Q2 in Cvx-stimulated platelets.z 1999 Federation of European Biochemical Societies.

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“…Syk and PLC ␥2 are tyrosine-phosphorylated upon GPVI activation by convulxin (25,30,32). Among the different proteins phosphorylated upon incubation of megakaryocytes with collagen or convulxin, bands with the same migration as p72…”

Section: Collagen and Convulxin Trigger Protein Tyrosine Phosphorylatmentioning

confidence: 99%

Expression and Function of the Collagen Receptor GPVI during Megakaryocyte Maturation

Lagrue-Lak-Hal

Debili

Kingbury³

et al. 2001

Journal of Biological Chemistry

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In this report, the expression and function of the platelet collagen receptor glycoprotein VI (GPVI) were studied in human megakaryocytes during differentiation and maturation of mobilized blood and cord blood derived CD34 ؉ cells. By flow cytometry, using an anti-GPVI monoclonal antibody or convulxin, a GPVI-specific ligand, GPVI was detected only on CD41؉ cells including some CD41 ؉ /CD34؉ cells, suggesting expression at a stage of differentiation similar to CD41. These results were confirmed at the mRNA level using reverse transcriptionpolymerase chain reaction. GPVI expression was low during megakaryocytic differentiation but increased in the more mature megakaryocytes (CD41 high ). As in platelets, megakaryocyte GPVI associates with the Fc receptor ␥ chain (FcR␥). The FcR ␥ chain was detected at the RNA and protein level at all stages of megakaryocyte maturation preceding the expression of GPVI. The other collagen receptor, ␣ 2 ␤ 1 integrin (CD49b/CD29), had a pattern of expression similar to GPVI. Megakaryocytic GPVI was recognized as a 55-kDa protein by immunoblotting and ligand blotting, and thus it presented a slightly lower apparent molecular mass than platelet GPVI (58 kDa). Megakaryocytes began to adhere to immobilized convulxin via GPVI after only 8 -10 days of culture, at a time when megakaryocytes were maturing. At this stage of maturation, they also adhered to immobilized collagen by ␣ 2 ␤ 1 integrin-dependent and -independent mechanisms. Convulxin induced a very similar pattern of protein tyrosine phosphorylation in megakaryocytes and platelets including Syk, FcR␥, and PLC ␥2 . Our results showed that GPVI is expressed early during megakaryocytic differentiation but functionally allows megakaryocyte adherence to collagen only at late stages of differentiation when its expression increases.At sites of vascular injury, platelets adhere and are activated by contact with collagen fibers exposed with the subendothelium matrix leading to thrombus formation. Several collagen receptors are present on platelets: integrin ␣ 2 ␤ 1 (CD49b/ CD29), GPIV 1 (CD36), GPVI, p65, and a recently cloned type III collagen receptor (1, 2). The direct interaction between collagen and integrin ␣ 2 ␤ 1 adheres platelets at the collagen surface, but platelet activation and thrombus formation and attachment are subsequently mainly supported by GPVI. In addition to collagen, two GPVI-specific ligands have been described: collagen-related peptides (3) and convulxin, a snake venom protein (4). GPVI has recently been characterized as a new member of the immunoglobulin superfamily of cell-associated receptors, in which expression is restricted to the hematopoietic lineage (5-7). It is coexpressed as a noncovalent complex with the common immunoglobulin receptor ␥ (FcR␥) chain, which acts as the signaling subunit of the complex (8, 9) As a consequence, signaling pathways coupled to GPVI dimerization are identical to those coupled to other immune receptors; tyrosine phosphorylation of the FcR ␥ chain on its immunoreceptor tyrosine-...

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Convulxin-induced platelet aggregation is accompanied by a powerful activation of the phospholipase C pathway

Cited by 27 publications

References 28 publications

The P2Y1receptor plays an essential role in the platelet shape change induced by collagen when TxA2 formation is prevented

The P2Y1receptor plays an essential role in the platelet shape change induced by collagen when TxA2 formation is prevented

Phosphatidylinositol 3′‐kinase and tyrosine‐phosphatase activation positively modulate Convulxin‐induced platelet activation. Comparison with collagen

Expression and Function of the Collagen Receptor GPVI during Megakaryocyte Maturation

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