A mutation in cytochrome c oxidase subunit VIa causes defective L-type calcium currents and Leigh syndrome-like phenotypes in Drosophila.

摘要

Voltage-dependent calcium channels mediate the influx of calcium ions in response to membrane depolarization. Dysfunction of calcium channels has been implicated in a wide rage of human diseases. Modulation of L-type calcium channels by second messenger-activated protein phosphorylation pathways has been demonstrated in a number of model systems.; The fruitfly, Drosophila, has been used as a model system to study a number of biological processes because of its amenability to genetic manipulation. Drosophila allows one to conduct large scale mutagenesis to isolate mutations with recognizable phenotypes. Dysfunction of ion channels has been associated with a number of temperature-sensitive paralytic mutants. A previously undescribed temperature sensitive paralytic mutant, levy1, has shown defective L-type calcium currents in the larval body-wall muscles. Identification of a levy1 mutation could reveal a novel pathway through which L-type calcium channels are modulated.; The levy1 mutation was mapped by genetic methods including recombination mapping, deficiency mapping, and male recombination mapping. Four levy deficiency lines were generated by P element mutagenesis. Genetic studies pointed out that gene CG17280, a homolog of human cytochrome c oxidase subunit VIa, was the candidate for the levy gene. Sequence analysis revealed a point mutation in gene CG17280 in the levy1 mutant. Gene CG17280 was identified as the levy gene by germline transformation. Identification of the levy gene suggests a potential pathway modulating L-type calcium channels by cytochrome c oxidase.; Further characterization demonstrated a number of other defects associated with the levy1 mutant. In addition to temperature-sensitive paralytic behavior, the levy1 mutant also exhibited bang-sensitivity in an age-dependent manner. Cytochrome c oxidase activity was reduced, and the lifespan of the levy1 mutant was shortened. Increased sensitivity to oxidative stress was indicated by its paraquat-sensitivity. Impaired ATP production was detected in the aged levy1 mutant. Spongiform neurodegeneration was observed in the levy1 mutant. The defects manifested in the levy1 mutant largely resemble Leigh syndrome, one of the most common diseases associated with COX deficiency. The levy1 mutant could be a suitable model to study the pathogenesis of COX-deficient Leigh syndrome and to screen for therapeutic treatments.