ATAD-3 couples plasma membrane injury to mitochondrial Ca2+ signaling.

Mitochondrial Ca2+ uptake couples cellular Ca2+ signals to mitochondrial metabolism and stress responses and is primarily mediated by the mitochondrial Ca2+ uniporter (MCU). Here, we identify an ATAD-3-dependent mechanism that promotes mitochondrial Ca2+ uptake following plasma membrane injury in C. elegans. Living imaging reveals robust, albeit delayed, mitochondrial Ca2+ influx following injury in mcu-1 mutants, indicating the existence of a compensatory Ca2+ uptake mechanism. RNAi screen identifies the conserved AAA+ ATPase ATAD-3 as an essential regulator of this pathway, whereas MICU-3 acts as a negative regulator. Wounding induces ATAD-3 oligomerization and mitochondrial enrichment, which are enhanced in mcu-1 mutants. Disrupting ATAD-3 oligomerization or expression of disease-associated ATAD-3 variants abolishes wounding-induced mitochondrial Ca2+ uptake. Structure modeling predicts that oligomeric ATAD-3 adopts a channel-like architecture. These findings uncover ATAD-3 as a context-dependent regulator of mitochondrial Ca2+ homeostasis during cellular stress and provide insight into how this process may be disrupted in disease.