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PI 3-kinase p110β: a new target for antithrombotic therapy


Platelet activation at sites of vascular injury is essential for the arrest of bleeding; however, excessive platelet accumulation at regions of atherosclerotic plaque rupture can result in the development of arterial thrombi, precipitating diseases such as acute myocardial infarction and ischemic stroke. Rheological disturbances (high shear stress) have an important role in promoting arterial thrombosis by enhancing the adhesive and signaling function of platelet integrin αIIbβ3 (GPIIb-IIIa). In this study we have defined a key role for the Type Ia phosphoinositide 3-kinase (PI3K) p110β isoform in regulating the formation and stability of integrin αIIbβ3 adhesion bonds, necessary for shear activation of platelets. Isoform-selective PI3K p110β inhibitors have been developed which prevent formation of stable integrin αIIbβ3 adhesion contacts, leading to defective platelet thrombus formation. In vivo, these inhibitors eliminate occlusive thrombus formation but do not prolong bleeding time. These studies define PI3K p110β as an important new target for antithrombotic therapy.

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Figure 1: PI3K promotes cytosolic calcium flux and stable platelet adhesion on immobilized fibrinogen following exposure to rapid increases in shear.
Figure 2: Development of a new PI3K p110β isoform–selective inhibitor.
Figure 3: PI3K p110β promotes cytosolic calcium flux and stable platelet adhesion in response to rapid increases in shear.
Figure 4: Role of PI3K p110β in promoting platelet activation in response to fluid shear stress or soluble agonists.
Figure 5: Role of PI3K p110β in regulating platelet activation induced by physiological agonists.
Figure 6: Antithrombotic activity of TGX-221.


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This work was supported by the National Health and Medical Research Council and the National Heart Foundation of Australia. Kinacia Pty Ltd also contributed financial support. We would like to thank L. Stephens, P. Hawkins and Z. Ruggeri for discussions, and D. Williamson, P. Mangin, K. Heel, D. Dunstan, I. Harper, and G. Currie, P. Freeman, M. Mulchandani, T. Domagala, M. Wang, N. Mistry, V. Strangis, S. Turnbull and T. Hinds for technical assistance and advice during the preparation of this manuscript.

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Correspondence to Shaun P Jackson.

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Competing interests

Vijaya Kenche, Hishani Prabaharan, Philip E. Thompson, Gregg D. Smith, Dilek Saylik, Sharelle A. Sturgeon, Catherine Jones and Lucy Lu were full time employees of Kinacia during the performance of these studies. A number of the authors have competing financial interests, primarily as shareholders in the biotechnology company Kinacia Pty Ltd (a wholly owned subsidiary of Cerylid Biosciences Ltd), which developed the inhibitors against PI 3-kinase p110beta. None of the authors currently own more than 1% stock in Cerylid Biosciences. Gregg D. Smith, Hishani Prabaharan and Dilek Saylik are currently full-time employees of Cerylid and Alan D. Robertson, James A. Angus and Christine E. Wright have consultancy arrangements with the company. This work was partially funded by Kinacia.

Supplementary information

Supplementary Fig. 1

Synthesis of TGX-221, a novel inhibitor of PI 3-kinase. (PDF 58 kb)

Supplementary Fig. 2

Role of PI3K p110δ and γ in shear-dependent platelet calcium flux in platelets. (PDF 62 kb)

Supplementary Fig. 3

Role of PI3K p110β in promoting platelet activation in response to physiological agonists (PDF 58 kb)

Supplementary Fig. 4

Effect of TGX-221 on P2Y1-dependent calcium flux and platelet shape change in ADP-stimulated platelets. (PDF 63 kb)

Supplementary Fig. 5

Antithrombotic effect of TGX-221. (PDF 69 kb)

Supplementary Fig. 6

Dration of the antithrombotic effect of TGX-221 following a single i.v. bolus. (PDF 40 kb)

Supplementary Table 1

Relative inhibitory potency of TGX-221 against a broad panel of lipid and protein kinases. (PDF 51 kb)

Supplementary Methods (PDF 56 kb)

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Jackson, S., Schoenwaelder, S., Goncalves, I. et al. PI 3-kinase p110β: a new target for antithrombotic therapy. Nat Med 11, 507–514 (2005).

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