ATP synthase subunits e and g are essential for Ca2+ homeostasis and development in Drosophila melanogaster independent of oxidative phosphorylation.

Abstract

Beyond its roles in ATP production and shaping cristae architecture, mitochondrial ATP synthase has been implicated in generating the permeability transition pore (PTP), a Ca2+-activated, high-conductance channel that leads to matrix swelling and cell death in mammalian cells. In Drosophila melanogaster, the PTP homolog rather forms a selective Ca2+-induced Ca2+-release (CICR) channel whose physiological relevance at the organism level remains poorly understood. Here, we down-regulated Drosophila subunits e and g, which are essential for PTP formation in yeast and mammalian cells. Ubiquitous down-regulation of either subunit caused larval developmental arrest, whereas tissue-specific suppression in muscle or neurons led to severe locomotor impairment. Dimerization was markedly reduced, altering mitochondrial ultrastructure while leaving respiratory capacity largely preserved. Strikingly, mitochondria from both knockdown animals accumulated larger Ca2+ loads, consistent with an impaired CICR. This was accompanied by near-complete loss of ecdysone, the Ca2+-dependent master hormone of metamorphosis. Neuron-specific knockdown flies displayed defective mitochondrial Ca2+ efflux and altered synaptic organization at the neuromuscular junction. Altogether, our findings establish that ATP synthase functions as a CICR channel controlling Ca2+ homeostasis, endocrine signaling and development in Drosophila.