title: The D-loop structure of human mtDNA is destabilized directly by 1-methyl-4-phenylpyridinium ion (MPP+), a parkinsonism-causing toxin.
abstract: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine has been reported to cause parkinsonism via its neurotoxic form, 1-methyl-4-phenylpyridinium ion (MPP+), which inhibits complex I of the mitochondrial respiratory chain. Its parkinsonism-causing mechanisms attract a great deal of interest as a model of the disease. Recently, we reported that MPP+ strongly decreases the amount of mtDNA independent of the inhibition of complex I. Maintenance of a proper amount of mtDNA is essential for the normal function of mitochondria as exemplified in many mitochondrial diseases. The most characteristic feature in vertebral mtDNA replication is that H-strand synthesis proceeds displacing the parental H-strand as a long single strand. It forms the D-loop, a triplex replication intermediate composed of the parental L-strand, nascent H-strand and displaced H-strand. Here we show that MPP+ does not inhibit DNA synthesis by DNA polymerase gamma, but rather releases the nascent H-strands from mtDNA both in organello and in vitro. This indicates that MPP+ directly destabilizes the D-loop structure, thereby inhibiting replication. This study raises a new mechanism, i.e. destabilization of replication intermediates, for depletion of mtDNA.
authors.affiliation: Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Umeda
authors.forename: T
authors.initials: T
authors.lastname: Muta
authors.forename: T
authors.initials: T
authors.lastname: Ohsato
authors.forename: C
authors.initials: C
authors.lastname: Takamatsu
authors.forename: N
authors.initials: N
authors.lastname: Hamasaki
authors.forename: D
authors.initials: D
authors.lastname: Kang
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000494:pharmacology*; D000074002:DNA Polymerase gamma; D004261:DNA Replication / Q000187:drug effects* / Q000235:genetics; D004272:DNA, Mitochondrial / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004278:DNA, Superhelical / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D006367:HeLa Cells; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D009690:Nucleic Acid Conformation / Q000187:drug effects*; D009691:Nucleic Acid Denaturation / Q000187:drug effects; D010302:Parkinson Disease, Secondary / Q000139:chemically induced* / Q000235:genetics; D011193:Potassium Iodide / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D004277:DNA, Single-Stranded; D004278:DNA, Superhelical; D011994:Recombinant Proteins; D011193:Potassium Iodide; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; D015655:1-Methyl-4-phenylpyridinium