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Involvement of Src kinases and PLCgamma2 in clot retraction.

Suzuki-Inoue K, Hughes CE, Inoue O, Kaneko M, Cuyun-Lira O, Takafuta T, Watson SP, Ozaki Y - Thromb. Res. (2006)

Bottom Line: In the present study, we demonstrate that the structurally distinct Src kinase inhibitors, PP2 and PD173952, significantly reduced the rate of clot retraction, but did not prevent it reaching completion.This effect was accompanied by abolition of alpha(IIb)beta(3)-dependent protein tyrosine phosphorylation, including PLCgamma2.Furthermore, platelet adhesion to fibrinogen leads to MLC phosphorylation through a pathway that is inhibited by PP2 and by the PLC inhibitor, U73122.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical and Laboratory Medicine, Faculty of Medicine, Yamanashi University, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan. katsuei@yamanashi.ac.jp

ABSTRACT
The integrin alpha(IIb)beta(3) plays a critical role in mediating clot retraction by platelets which is important in vivo in consolidating thrombus formation. Actin-myosin interaction is essential for clot retraction. In the present study, we demonstrate that the structurally distinct Src kinase inhibitors, PP2 and PD173952, significantly reduced the rate of clot retraction, but did not prevent it reaching completion. This effect was accompanied by abolition of alpha(IIb)beta(3)-dependent protein tyrosine phosphorylation, including PLCgamma2. A role for PLCgamma2 in mediating clot retraction was demonstrated using PLCgamma2-deficient murine platelets. Furthermore, platelet adhesion to fibrinogen leads to MLC phosphorylation through a pathway that is inhibited by PP2 and by the PLC inhibitor, U73122. These results demonstrate a partial role for Src kinase-dependent activation of PLCgamma2 and MLC phosphorylation in mediating clot retraction downstream of integrin alpha(IIb)beta(3).

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Related in: MedlinePlus

Multiple mechanisms of regulation of the contractile apparatus underlie clot retraction. Thrombin receptors are able to regulate clot retraction through activation of PLCβ and Rho kinase. αIIbβ3 outside-in signalling is required for optimal clot retraction through bifurcating signals, namely activation of PLCγ2 and phosphorylation of the diY motif, which combine to mediate clot retraction. This interaction could occur by recruitment of myosin to the phosphorylated diY motif in combination of activation of MLC kinase downstream of PLCγ2.
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fig5: Multiple mechanisms of regulation of the contractile apparatus underlie clot retraction. Thrombin receptors are able to regulate clot retraction through activation of PLCβ and Rho kinase. αIIbβ3 outside-in signalling is required for optimal clot retraction through bifurcating signals, namely activation of PLCγ2 and phosphorylation of the diY motif, which combine to mediate clot retraction. This interaction could occur by recruitment of myosin to the phosphorylated diY motif in combination of activation of MLC kinase downstream of PLCγ2.

Mentions: The present study demonstrates that αIIbβ3 outside-in signalling is required for optimal clot retraction in thrombin-stimulated platelets through a pathway that is partially dependent on Src kinases and PLCγ2. Significantly, however, this αIIbβ3-regulated cascade is not essential for completion of clot retraction, most likely because clot retraction is regulated through a number of additional pathways, including activation of PLCβ and Rho kinase, and αIIbβ3-regulation of PLCγ1, which is expressed in low level in mouse platelets [14]. A schematic summarizing these results is shown in Fig. 5. As expected, however, clot retraction is absolutely dependent on myosin contractility, as demonstrated using the inhibitor of myosin II, blebbistatin. The present results therefore indicate that clot retraction in thrombin-stimulated platelets is regulated through multiple pathways, including thrombin-dependent activation of PLCβ and Rho kinase, which activate MLC kinase and inhibit MLC phosphatase, respectively, and αIIbβ3-regulation of PLCγ2, mediated downstream of Src kinase activation (Fig. 5).


Involvement of Src kinases and PLCgamma2 in clot retraction.

Suzuki-Inoue K, Hughes CE, Inoue O, Kaneko M, Cuyun-Lira O, Takafuta T, Watson SP, Ozaki Y - Thromb. Res. (2006)

Multiple mechanisms of regulation of the contractile apparatus underlie clot retraction. Thrombin receptors are able to regulate clot retraction through activation of PLCβ and Rho kinase. αIIbβ3 outside-in signalling is required for optimal clot retraction through bifurcating signals, namely activation of PLCγ2 and phosphorylation of the diY motif, which combine to mediate clot retraction. This interaction could occur by recruitment of myosin to the phosphorylated diY motif in combination of activation of MLC kinase downstream of PLCγ2.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1884692&req=5

fig5: Multiple mechanisms of regulation of the contractile apparatus underlie clot retraction. Thrombin receptors are able to regulate clot retraction through activation of PLCβ and Rho kinase. αIIbβ3 outside-in signalling is required for optimal clot retraction through bifurcating signals, namely activation of PLCγ2 and phosphorylation of the diY motif, which combine to mediate clot retraction. This interaction could occur by recruitment of myosin to the phosphorylated diY motif in combination of activation of MLC kinase downstream of PLCγ2.
Mentions: The present study demonstrates that αIIbβ3 outside-in signalling is required for optimal clot retraction in thrombin-stimulated platelets through a pathway that is partially dependent on Src kinases and PLCγ2. Significantly, however, this αIIbβ3-regulated cascade is not essential for completion of clot retraction, most likely because clot retraction is regulated through a number of additional pathways, including activation of PLCβ and Rho kinase, and αIIbβ3-regulation of PLCγ1, which is expressed in low level in mouse platelets [14]. A schematic summarizing these results is shown in Fig. 5. As expected, however, clot retraction is absolutely dependent on myosin contractility, as demonstrated using the inhibitor of myosin II, blebbistatin. The present results therefore indicate that clot retraction in thrombin-stimulated platelets is regulated through multiple pathways, including thrombin-dependent activation of PLCβ and Rho kinase, which activate MLC kinase and inhibit MLC phosphatase, respectively, and αIIbβ3-regulation of PLCγ2, mediated downstream of Src kinase activation (Fig. 5).

Bottom Line: In the present study, we demonstrate that the structurally distinct Src kinase inhibitors, PP2 and PD173952, significantly reduced the rate of clot retraction, but did not prevent it reaching completion.This effect was accompanied by abolition of alpha(IIb)beta(3)-dependent protein tyrosine phosphorylation, including PLCgamma2.Furthermore, platelet adhesion to fibrinogen leads to MLC phosphorylation through a pathway that is inhibited by PP2 and by the PLC inhibitor, U73122.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical and Laboratory Medicine, Faculty of Medicine, Yamanashi University, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan. katsuei@yamanashi.ac.jp

ABSTRACT
The integrin alpha(IIb)beta(3) plays a critical role in mediating clot retraction by platelets which is important in vivo in consolidating thrombus formation. Actin-myosin interaction is essential for clot retraction. In the present study, we demonstrate that the structurally distinct Src kinase inhibitors, PP2 and PD173952, significantly reduced the rate of clot retraction, but did not prevent it reaching completion. This effect was accompanied by abolition of alpha(IIb)beta(3)-dependent protein tyrosine phosphorylation, including PLCgamma2. A role for PLCgamma2 in mediating clot retraction was demonstrated using PLCgamma2-deficient murine platelets. Furthermore, platelet adhesion to fibrinogen leads to MLC phosphorylation through a pathway that is inhibited by PP2 and by the PLC inhibitor, U73122. These results demonstrate a partial role for Src kinase-dependent activation of PLCgamma2 and MLC phosphorylation in mediating clot retraction downstream of integrin alpha(IIb)beta(3).

Show MeSH
Related in: MedlinePlus