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

The mitochondrial calcium uniporter (MCU), a selective intracellular calcium (Ca²⁺) channel, mediates mitochondrial Ca²⁺ uptake, supporting Ca²⁺ homeostasis and mitochondrial bioenergetics. While cytosolic Ca²⁺ flux from the dense tubular system (DTS) and store-operated Ca²⁺ entry are known to drive platelet activation, the role of mitochondrial Ca²⁺ handling in platelet function and thrombosis is not well understood.

This study examined whether targeting MCU-dependent Ca²⁺ flux could attenuate platelet activation and arterial thrombosis.

Susceptibility to arterial thrombosis was assessed using the FeCl₃-induced carotid injury model in wild-type and MCU^-/- mice. Mitochondrial and cytosolic Ca²⁺ levels were measured in Rhod-2- and Fura-2-loaded platelets by fluorometry, and platelet bioenergetics were analyzed using a Seahorse extracellular flux analyzer.

Genetic ablation of MCU inhibited agonist-induced platelet functions, including aggregation, fibrinogen binding to integrin α_IIbβ₃, granule secretion, and spreading on fibrinogen. MCU^-/- mice were less susceptible to in vivo arterial thrombosis with unaltered tail bleeding time, suggesting normal hemostasis. Mechanistically, these effects were associated with disruption of Ca²⁺ homeostasis mediated by reduced mitochondrial Ca²⁺ uptake, altered release of Ca²⁺ from dense tubular system, and impaired store-operated Ca²⁺ entry in agonist-stimulated MCU^-/- platelets. Consistent with this, Ca²⁺-dependent glycoprotein VI signaling events such as phospholipase γ2 and protein kinase C substrate phosphorylation were significantly reduced in collagen-stimulated MCU^-/- platelets. Furthermore, disruption of mitochondrial Ca²⁺ uptake significantly impaired mitochondrial respiration and associated adenosine triphosphate production in agonist-stimulated MCU^-/- platelets.

MCU facilitates platelet activation and thrombosis by regulating calcium flux (mitochondrial and cytosolic), thereby establishing its potential as a target for antithrombotic therapeutic intervention.