Cellular adaptation of mitochondrial metabolism and biogenesis in response to partial ATP synthase uncoupling

Abstract

Cellular energy metabolism relies on tight regulation of mitochondrial biogenesis and turnover to maintain bioenergetic homeostasis. Understanding the signaling pathways that modulate mitochondrial content in response to changing energetic demands is therefore essential. This work examines how partial mitochondrial uncoupling reshapes mitochondrial content and metabolism in yeast and how such adaptations mirror features of pathological or age-associated states. Using a Saccharomyces cerevisiae ATP synthase mutant lacking the epsilon subunit ({Delta}{varepsilon}) and carrying a compensatory mutation that allows survival under uncoupling ({Delta}{varepsilon}+c-L57F), mitochondrial abundance, organization, and function were compared with those of wild-type and rescue strains (mutant re-expressing the epsilon subunit of the ATP synthase). Analyses included respiration assays, mitochondrial DNA quantification, {beta}-galactosidase reporters, fluorescence microscopy of the mitochondrial network, and 2D-DiGE proteomics. Uncoupling in the mutant led to a strong increase in mitochondrial mass per cell, higher respiratory capacity, elevated cytochrome levels, and increased mtDNA copy number, together with augmented transcriptional activity consistent with activation of HAP-dependent mitochondrial biogenesis. Despite a fragmented network, mitochondria retained typical ultrastructural features, while proteomic profiling indicated a shift toward ATP production via substrate-level phosphorylation. Overall, partial uncoupling promotes reversible mitochondrial biogenesis and metabolic remodeling that depend on a preserved proton-motive force, highlighting mitochondrial signaling as a key regulator of cellular energy homeostasis and offer new perspectives for studying metabolic disorders and mitochondrial pathologies. GRAPHICAL ABSTRACTS O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=179 SRC="FIGDIR/small/695256v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@19b1eceorg.highwire.dtl.DTLVardef@103a6ceorg.highwire.dtl.DTLVardef@bc48f6org.highwire.dtl.DTLVardef@15a191c_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIMitochondrial uncoupling triggers a marked increase in mitochondrial biogenesis in yeast. C_LIO_LIUncoupling leads to fragmentation of the mitochondrial network, while preserving mitochondrial ultrastructure. C_LIO_LIUncoupling induces metabolic remodeling that favors ATP production through substrate-level phosphorylation. C_LIO_LIThese cellular adaptations are reversible upon re-establishment of mitochondrial coupling. C_LIO_LIThe proton motive force serves as a key signal sensed by the cell. C_LI