Combined deficiency of PI3KC2α and PI3KC2β reveals a nonredundant role for PI3KC2α in regulating mouse platelet structure and thrombus stability

Abstract

The physiological functions and cellular signaling of Class II phosphoinositide 3-kinases (PI3Ks) remain largely unknown. Platelets express two Class II PI3Ks: PI3KC2α and PI3KC2β. PI3KC2α deficiency was recently reported to cause disruption of the internal membrane reserve structure of platelets (open canalicular system, OCS) that results in dysregulated platelet adhesion and impaired arterial thrombosis in vivo. Notably, these effects on platelets occurred despite normal agonist-induced 3-phosphorylated phosphoinositide (3-PPI) production and cellular activation in PI3KC2α-deficient platelets. However, the potential compensatory actions of PI3KC2β in platelets have not yet been investigated. Here, we report the first mice deficient in both PI3KC2α and PI3KC2β (no Class II PI3Ks in platelets) and reveal a nonredundant role for PI3KC2α in mouse platelet structure and function. Specifically, we show that the disrupted OCS and impaired thrombus stability observed in PI3KC2α-deficient platelets does not occur in PI3KC2β-deficient platelets and is not exaggerated in platelets taken from mice deficient in both enzymes. Furthermore, detailed examination of 3-PPI production in platelets from this series of mice revealed no changes in either unactivated or activated platelets, including those with a complete lack of Class II PI3Ks. These findings indicate a nonredundant role for PI3KC2α in regulating platelet structure and function, and suggest that Class II PI3Ks do not significantly contribute to the acute agonist-induced production of 3-PPIs in these cells.

Keywords:

• Phosphoinositide 3-kinases
• PI3KC2α
• PI3KC2β
• platelets

Acknowledgments

Justin R. Hamilton was supported by a Future Fellowship from the Australian Research Council. The authors thank the staff of AMREP Animal Services for animal husbandry and support; Stephen Cody from Monash Micro Imaging for microscopy support; Stephanie Orive for technical support; and F. L. Arena for valuable contributions during the course of this study.

Funding

This work was supported by grants from the NHMRC to Justin R. Hamilton (1010848 and 1047295).

Declaration of interest

The authors report no conflicts of interests.

Additional information

Funding

This work was supported by grants from the NHMRC to Justin R. Hamilton (1010848 and 1047295).