SummaryA plethora of cellular processes, including apoptosis, depend on regulated changes in mitochondrial shape and ultrastructure. Scarce is our understanding of the role of mitochondria and of their morphology during autophagy, a bulk degradation and recycling process of eukaryotic cells’ constituents. Here we show that mitochondrial morphology determines the cellular response to macroautophagy. When autophagy is triggered, mitochondria elongate in vitro and in vivo. Upon starvation cellular cAMP levels increase and protein kinase A (PKA) becomes activated. PKA in turn phosphorylates the pro-fission dynamin related protein 1 (DRP1) that is therefore retained in the cytoplasm, leading to unopposed mitochondrial fusion. Elongated mitochondria are spared from autophagic degradation, possess more cristae, increase dimerization and activity of ATP synthase, and maintain ATP production. When elongation is genetically or pharmacologically blocked, mitochondria conversely consume ATP, precipitating starvation-induced death. Thus, regulated changes in mitochondrial morphology determine the fate of the cell during autophagy.
SummaryRespiratory chain complexes assemble into functional quaternary structures called supercomplexes (RCS) within the folds of the inner mitochondrial membrane, or cristae. Here, we investigate the relationship between respiratory function and mitochondrial ultrastructure and provide evidence that cristae shape determines the assembly and stability of RCS and hence mitochondrial respiratory efficiency. Genetic and apoptotic manipulations of cristae structure affect assembly and activity of RCS in vitro and in vivo, independently of changes to mitochondrial protein synthesis or apoptotic outer mitochondrial membrane permeabilization. We demonstrate that, accordingly, the efficiency of mitochondria-dependent cell growth depends on cristae shape. Thus, RCS assembly emerges as a link between membrane morphology and function.
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