Abstract
Metabolic function and architecture of mitochondria are intimately linked. More than 60 years ago, cristae were discovered as characteristic elements of mitochondria that harbor the protein complexes of oxidative phosphorylation, but how cristae are formed, remained an open question. Here we present experimental results obtained with yeast that support a novel hypothesis on the existence of two molecular pathways that lead to the generation of lamellar and tubular cristae. Formation of lamellar cristae depends on the mitochondrial fusion machinery through a pathway that is required also for homeostasis of mitochondria and mitochondrial DNA. Tubular cristae are formed via invaginations of the inner boundary membrane by a pathway independent of the fusion machinery. Dimerization of the F1FO-ATP synthase and the presence of the MICOS complex are necessary for both pathways. The proposed hypothesis is suggested to apply also to higher eukaryotes, since the key components are conserved in structure and function throughout evolution.
Highlights
Mitochondria have a multitude of functions in the eukaryotic cell
Major advances have been made in our understanding of the biogenesis of mitochondrial protein complexes and supercomplexes, but the biogenesis of mitochondrial architecture, the higher level of organization, has been investigated to a much lesser degree
It is known that dysfunction of the components that mediate mitochondrial membrane fusion, Fzo1, Ugo1, and Mgm1, leads to loss of mtDNA and loss of cristae, concomitant with septa formation and inhibition of inner membrane (IM) fusion (Hermann et al, 1998; Hoppins et al, 2009; Meeusen et al, 2006; Sesaki et al, 2003)
Summary
Mitochondria have a multitude of functions in the eukaryotic cell. They perform respiration-dependent energy transduction to generate proton-motive force and ATP, and house a large number of metabolic enzymes. They have their own genetic system but are closely connected with the rest of the cell by a number of pathways, such as metabolite, protein and lipid transport, protein quality control, autophagy and apoptosis. Mitochondria are dynamic organelles undergoing continual fission and fusion (Bereiter-Hahn and Voth, 1994). The dynamics of mitochondria is essential for their function as well as maintenance, inheritance and integrity of their DNA (mtDNA). Recent research has revealed the involvement of this organelle in a multitude of human pathological conditions, including neurodegeneration, cardiomyopathies, metabolic diseases and cancer (Chan, 2012; Costa and Scorrano, 2012; Itoh et al, 2013; Mourier et al, 2014; Nunnari and Suomalainen, 2012; Pickrell and Youle, 2013; Youle and van der Bliek, 2012)
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