Modulating longevity in Drosophila by over- and underexpression of glutamate-cysteine ligase.

A notable extension of life span (up to 50%) was achieved in Drosophila melanogaster when the catalytic subunit of glutamate-cysteine ligase (GCLc) was overexpressed in neuronal tissue, while a moderate increase (up to 24%) was observed when the modulatory subunit of GCL (GCLm) was overexpressed globally. We sought to identify specific tissue domains that are particularly sensitive to the beneficial effects of GCLc overexpression. Overexpression of GCLc using the mushroom body driver (OK107-GAL4) had a small but significant beneficial effect on longevity (approximately 12%) while overexpression in serotonergic (MZ360-GAL4) neurons or dopaminergic and serotonergic neurons (Ddc-GAL4) had small, nonsignificant effects on longevity. A significant beneficial effect (12-13%) was also observed using the C23-GAL4 transverse muscle driver. Finally, a low-level global driver (armadillo) was shown to increase life span significantly (15%). A series of mutant and knockdown studies were also carried out. Reduction of GCLm by > 95% had no discernable effect on longevity or resistance to oxidative stress. In contrast, knockdown of GCLc by 30-70% using an RNAi-hairpin strategy had a significant effect, resulting in greater sensitivity to H(2)O(2) and reduced survivorship under normal conditions varying from a 50% reduction in median life span to lethality. A GCLc null allele was identified and shown to be recessive lethal. Overall, this study demonstrates that the longevity effects of GCLc are dependent on dosage and that there are specific tissues (mushroom bodies, motor neurons, and transverse muscle cells) particularly sensitive to the benefits of GCLc overexpression.

Overexpression of glutamate-cysteine ligase extends life span in Drosophila melanogaster.

The hypothesis that overexpression of glutamate-cysteine ligase (GCL), which catalyzes the rate-limiting reaction in de novo glutathione biosynthesis, could extend life span was tested in the fruit fly, Drosophila melanogaster. The GAL4-UAS binary transgenic system was used to generate flies overexpressing either the catalytic (GCLc) or modulatory (GCLm) subunit of this enzyme, in a global or neuronally targeted pattern. The GCL protein content of the central nervous system was elevated dramatically in the presence of either global or neuronal drivers. GCL activity was increased in the whole body or in heads, respectively, of GCLc transgenic flies containing global or neuronal drivers. The glutathione content of fly homogenates was increased by overexpression of GCLc or GCLm, particularly in flies overexpressing either subunit globally, or in the heads of GCLc flies possessing neuronal drivers. Neuronal overexpression of GCLc in a long-lived background extended mean and maximum life spans up to 50%, without affecting the rate of oxygen consumption by the flies. In contrast, global overexpression of GCLm extended the mean life span only up to 24%. These results demonstrate that enhancement of the glutathione biosynthetic capability, particularly in neuronal tissues, can extend the life span of flies, and thus support the oxidative stress hypothesis of aging.