Dissection of autophagy in human platelets.

Continuous turnover of intracellular components by autophagy is necessary to preserve cellular homeostasis in all tissues. Despite recent advances in identifying autophagy-related genes and understanding the functions of autophagy in developmental and pathological conditions, so far, the role of autophagy in platelet, a specific anucleate cell type, is poorly understood. In this study, we showed that human platelets express the autophagy-related proteins ATG5, ATG7, and LC3. The same as in nucleated mammalian cells, autophagy was stimulated by cell starvation or the MTOR inhibitor rapamycin in a phosphatidylinositol 3-kinase (PtdIns3K)-dependent manner. Disruption of autophagic flux led to impairment of platelet aggregation and adhesion. Furthermore, Becn1 heterozygous knockout mice displayed a prolonged bleeding time and reduced platelet aggregation. These results suggest a potential role of autophagy in the regulation of platelet function, and imply that gene transcription may not be an essential prerequisite for adaptive autophagy.