adPEO mutations in ANT1 impair ADP-ATP translocation in muscle mitochondria.

Abstract

Mutations in the heart and muscle isoform of adenine nucleotide translocator 1 (ANT1) are associated with autosomal-dominant progressive external opthalmoplegia (adPEO) clinically characterized by exercise intolerance, ptosis and muscle weakness. The pathogenic mechanisms underlying the mitochondrial myopathy caused by ANT1 mutations remain largely unknown. In yeast, expression of ANT1 carrying mutations corresponding to the human adPEO ones causes a wide range of mitochondrial abnormalities. However, functional studies of ANT1 mutations in mammalian cells are lacking, because they have been hindered by the fact that ANT1 expression leads to apoptotic cell death in commonly utilized replicating cell lines. Here, we successfully express functional ANT1 in differentiated mouse myotubes, which naturally contain high levels of ANT1, without causing cell death. We demonstrate, for the first time in these disease-relevant mammalian cells, that mutant human ANT1 causes dominant mitochondrial defects characterized by decreased ADP-ATP exchange function and abnormal translocator reversal potential. These abnormalities are not due to ANT1 loss of function, because knocking down Ant1 in myotubes causes functional changes different from ANT1 mutants. Under certain physiological conditions, mitochondria consume ATP to maintain membrane potential by reversing the ADP-ATP transport. The modified properties of mutant ANT1 can be responsible for disease pathogenesis in adPEO, because exchange reversal occurring at higher than normal membrane potential can cause excessive energy depletion and nucleotide imbalance in ANT1 mutant muscle cells.

• Authors: Hibiki Kawamata, Valeria Tiranti, Jordi Magrané, Christos Chinopoulos, Giovanni Manfredi
• Journal: Human molecular genetics (Hum Mol Genet) Vol. 20 Issue 15 Pg. 2964-74 (Aug 01 2011) ISSN: 1460-2083 [Electronic] England
• PMID: 21586654 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Adenine Nucleotide Translocator 1
• Adenosine Diphosphate
• Adenosine Triphosphate

Topics

• Adenine Nucleotide Translocator 1 (genetics, metabolism)
• Adenosine Diphosphate (metabolism)
• Adenosine Triphosphate (metabolism)
• Animals
• Apoptosis (genetics)
• Blotting, Western
• Cell Line
• Cell Survival
• Electrophoresis, Polyacrylamide Gel
• Humans
• Immunohistochemistry
• Mice
• Mitochondria, Muscle (metabolism)
• Mutation
• Reverse Transcriptase Polymerase Chain Reaction