The mitochondrial calcium uniporter regulates calcium dynamics to drive platelet function, bioenergetics, and thrombosis.

Abstract

BACKGROUND: The mitochondrial calcium uniporter (MCU), a selective intracellular calcium (Ca) channel, mediates mitochondrial Cauptake, supporting Cahomeostasis and mitochondrial bioenergetics. While cytosolic Caflux from the dense tubular system (DTS) and store-operated Caentry are known to drive platelet activation, the role of mitochondrial Cahandling in platelet function and thrombosis is not well understood. OBJECTIVES: This study examined whether targeting MCU-dependent Caflux could attenuate platelet activation and arterial thrombosis. METHODS: Susceptibility to arterial thrombosis was assessed using the FeCl-induced carotid injury model in wild-type and MCUmice. Mitochondrial and cytosolic Calevels were measured in Rhod-2- and Fura-2-loaded platelets by fluorometry, and platelet bioenergetics were analyzed using a Seahorse extracellular flux analyzer. RESULTS: Genetic ablation of MCU inhibited agonist-induced platelet functions, including aggregation, fibrinogen binding to integrin αβ, granule secretion, and spreading on fibrinogen. MCUmice were less susceptible to in vivo arterial thrombosis with unaltered tail bleeding time, suggesting normal hemostasis. Mechanistically, these effects were associated with disruption of Cahomeostasis mediated by reduced mitochondrial Cauptake, altered release of Cafrom dense tubular system, and impaired store-operated Caentry in agonist-stimulated MCUplatelets. Consistent with this, Ca-dependent glycoprotein VI signaling events such as phospholipase γ2 and protein kinase C substrate phosphorylation were significantly reduced in collagen-stimulated MCUplatelets. Furthermore, disruption of mitochondrial Cauptake significantly impaired mitochondrial respiration and associated adenosine triphosphate production in agonist-stimulated MCUplatelets. CONCLUSION: MCU facilitates platelet activation and thrombosis by regulating calcium flux (mitochondrial and cytosolic), thereby establishing its potential as a target for antithrombotic therapeutic intervention.