Advertisement

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 and Sonia Severin

Key points

  • Vps34 controls intracellular trafficking, migration and platelet production in megakaryocytes.

  • Vps34 and its stimulation-dependent PI3P production regulate platelet secretion and thrombus growth

Abstract

To uncover the role of Vps34, the sole class III phosphoinositide 3-kinase, 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. While Vps34 deficiency did not impact on MK polyploidisation or proplatelet formation, it dampened MK granule biogenesis and directional migration towards 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 while the stimulation-dependent pool of PI3P was significantly decreased. Accordingly, a significant increase in the specific activity of Vps34 lipid kinase was observed following acute platelet stimulation. Similar as in Vps34-deficient platelets, ex vivo treatment of WT mouse or human platelets with 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, independently from its role in MKs. In vivo, Vps34 deficiency had no impact on tail bleeding time but significantly reduced platelet prothrombotic capacity following 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.

  • Submitted April 26, 2017.
  • Accepted September 1, 2017.