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Dynamic subcompartmentalization of the mitochondrial inner membrane.

ABSTRACT: The inner membrane of mitochondria is organized in two morphologically distinct domains, the inner boundary membrane (IBM) and the cristae membrane (CM), which are connected by narrow, tubular cristae junctions. The protein composition of these domains, their dynamics, and their biogenesis and maintenance are poorly understood at the molecular level. We have used quantitative immunoelectron microscopy to determine the distribution of a collection of representative proteins in yeast mitochondria belonging to seven major processes: oxidative phosphorylation, protein translocation, metabolite exchange, mitochondrial morphology, protein translation, iron-sulfur biogenesis, and protein degradation. We show that proteins are distributed in an uneven, yet not exclusive, manner between IBM and CM. The individual distributions reflect the physiological functions of proteins. Moreover, proteins can redistribute between the domains upon changes of the physiological state of the cell. Impairing assembly of complex III affects the distribution of partially assembled subunits. We propose a model for the generation of this dynamic subcompartmentalization of the mitochondrial inner membrane.

SUBMITTER: Vogel F

PROVIDER: S-EPMC2064565 | biostudies-literature | 2006 Oct

REPOSITORIES: biostudies-literature

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Dynamic subcompartmentalization of the mitochondrial inner membrane.

Vogel Frank F Bornhövd Carsten C Neupert Walter W Reichert Andreas S AS

The Journal of cell biology 20061016 2

The inner membrane of mitochondria is organized in two morphologically distinct domains, the inner boundary membrane (IBM) and the cristae membrane (CM), which are connected by narrow, tubular cristae junctions. The protein composition of these domains, their dynamics, and their biogenesis and maintenance are poorly understood at the molecular level. We have used quantitative immunoelectron microscopy to determine the distribution of a collection of representative proteins in yeast mitochondria ...[more]

PMID: 17043137

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Project description:Mitochondria are highly dynamic organelles that continuously move, fuse and divide. Mitochondrial dynamics modulate overall mitochondrial morphology and are essential for the proper function, maintenance and transmission of mitochondria and mitochondrial DNA (mtDNA). We have investigated mitochondrial fusion in yeast cells with severe defects in oxidative phosphorylation (OXPHOS) due to removal or various specific mutations of mtDNA. We find that, under fermentative conditions, OXPHOS deficient cells maintain normal levels of cellular ATP and ADP but display a reduced mitochondrial inner membrane potential. We demonstrate that, despite metabolic compensation by glycolysis, OXPHOS defects are associated to a selective inhibition of inner but not outer membrane fusion. Fusion inhibition was dominant and hampered the fusion of mutant mitochondria with wild-type mitochondria. Inhibition of inner membrane fusion was not systematically associated to changes of mitochondrial distribution and morphology, nor to changes in the isoform pattern of Mgm1, the major fusion factor of the inner membrane. However, inhibition of inner membrane fusion correlated with specific alterations of mitochondrial ultrastructure, notably with the presence of aligned and unfused inner membranes that are connected to two mitochondrial boundaries. The fusion inhibition observed upon deletion of OXPHOS related genes or upon removal of the entire mtDNA was similar to that observed upon introduction of point mutations in the mitochondrial ATP6 gene that are associated to neurogenic ataxia and retinitis pigmentosa (NARP) or to maternally inherited Leigh Syndrome (MILS) in humans. Our findings indicate that the consequences of mtDNA mutations may not be limited to OXPHOS defects but may also include alterations in mitochondrial fusion. Our results further imply that, in healthy cells, the dominant inhibition of fusion could mediate the exclusion of OXPHOS-deficient mitochondria from the network of functional, fusogenic mitochondria.

Dataset Information

Dynamic subcompartmentalization of the mitochondrial inner membrane.

Publications

Dynamic subcompartmentalization of the mitochondrial inner membrane.

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