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A Dual Role for the Class III PI3K, Vps34, in Platelet Production and Thrombus Growth

A Dual Role for the Class III PI3K, Vps34, in Platelet Production and Thrombus Growth

Colin Valet, Marie Levade, Gaëtan Chicanne, Benoit Bilanges, Cendrine Cabou, Julien Viaud, Marie-Pierre Gratacap, Frédérique Gaits-Iacovoni, Bart Vanhaesebroeck, Bernard Payrastre, Sonia Severin

Blood. 2017 Nov 2;130(18):2032-2042.

PMID: 28903944

Abstract:

To uncover the role of Vps34, the sole class III phosphoinositide 3-kinase (PI3K), in megakaryocytes (MKs) and platelets, we created a mouse model with Vps34 deletion in the MK/platelet lineage (Pf4-Cre/Vps34lox/lox). Deletion of Vps34 in MKs led to the loss of its regulator protein, Vps15, and was associated with microthrombocytopenia and platelet granule abnormalities. Although Vps34 deficiency did not affect MK polyploidisation or proplatelet formation, it dampened MK granule biogenesis and directional migration toward an SDF1α gradient, leading to ectopic platelet release within the bone marrow. In MKs, the level of phosphatidylinositol 3-monophosphate (PI3P) was significantly reduced by Vps34 deletion, resulting in endocytic/trafficking defects. In platelets, the basal level of PI3P was only slightly affected by Vps34 loss, whereas the stimulation-dependent pool of PI3P was significantly decreased. Accordingly, a significant increase in the specific activity of Vps34 lipid kinase was observed after acute platelet stimulation. Similar to Vps34-deficient platelets, ex vivo treatment of wild-type mouse or human platelets with the Vps34-specific inhibitors, SAR405 and VPS34-IN1, induced abnormal secretion and affected thrombus growth at arterial shear rate, indicating a role for Vps34 kinase activity in platelet activation, independent from its role in MKs. In vivo, Vps34 deficiency had no impact on tail bleeding time, but significantly reduced platelet prothrombotic capacity after carotid injury. This study uncovers a dual role for Vps34 as a regulator of platelet production by MKs and as an unexpected regulator of platelet activation and arterial thrombus formation dynamics.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
IAR42416324	VPS34 human			Price

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