Loss of the mitochondrial kinase PINK1 does not alter platelet function

PTEN-induced putative kinase (PINK) 1 is regarded as a master regulator of cellular mitophagy such that loss of function mutations contribute to early onset Parkinson's disease, through aberrant mitochondrial control and function. Mitochondrial function is key to platelet procoagulant activity, controlling the haemostatic response to vessel injury, but can also predispose blood vessels to thrombotic complications. Here, we sought to determine the role of PINK1 in platelet mitochondrial health and function using PINK1 knockout (KO) mice. The data largely show an absence of such a role. Haematological analysis of blood counts from KO mice was comparable to wild type. Quantification of mitochondrial mass by citrate synthase activity assay or expression of mitochondrial markers were comparable, suggesting normal mitophagy in KO platelets. Analysis of mitochondrial permeability transition pore opening, changes in mitochondrial membrane potential and calcium signalling to platelet activation were unaffected by loss of PINK1, whereas subtle enhancements of activation-induced reactive oxygen species were detected. Platelet aggregation, integrin activation, alpha- and dense granule secretion and phosphatidylserine exposure were unaltered in KO platelets while mouse tail bleeding responses were similar to wild type. Together these results demonstrate that PINK1 does not regulate basal platelet mitophagy and is dispensable for platelet function.