Adrenergic signaling regulates mitochondrial Ca²⁺ uptake through Pyk2-dependent tyrosine phosphorylation of the mitochondrial Ca²⁺ uniporter

Aims: Mitochondrial Ca<sup>2+</sup> homeostasis is crucial for balancing cell survival and death. The recent discovery of the molecular identity of the mitochondrial Ca<sup>2+</sup> uniporter pore (MCU) opens new possibilities for applying genetic approaches to study mitochondrial Ca<sup>2+</sup> regulation in various cell types, including cardiac myocytes. Basal tyrosine phosphorylation of MCU was reported from mass spectroscopy of human and mouse tissues, but the signaling pathways that regulate mitochondrial Ca<sup>2+</sup> entry through posttranslational modifications of MCU are completely unknown. Therefore, we investigated α1-adrenergic-mediated signal transduction of MCU posttranslational modification and function in cardiac cells.<p></p> Results: α1-adrenoceptor (α1-AR) signaling translocated activated proline-rich tyrosine kinase 2 (Pyk2) from the cytosol to mitochondrial matrix and accelerates mitochondrial Ca<sup>2+</sup> uptake via Pyk2-dependent MCU phosphorylation and tetrametric MCU channel pore formation. Moreover, we found that α1-AR stimulation increases reactive oxygen species production at mitochondria, mitochondrial permeability transition pore activity, and initiates apoptotic signaling via Pyk2-dependent MCU activation and mitochondrial Ca<sup>2+</sup> overload.<p></p> Innovation: Our data indicate that inhibition of α1-AR-Pyk2-MCU signaling represents a potential novel therapeutic target to limit or prevent mitochondrial Ca<sup>2+</sup> overload, oxidative stress, mitochondrial injury, and myocardial death during pathophysiological conditions, where chronic adrenergic stimulation is present. Conclusion: The α1-AR-Pyk2-dependent tyrosine phosphorylation of the MCU regulates mitochondrial Ca<sup>2+</sup> entry and apoptosis in cardiac cells. Antioxid. Redox Signal. 21, 863–879