Overexpression of Glucose-6-phosphate Dehydrogenase Extends the Life Span of Drosophila melanogaster

Rajindar S. Sohal,Robin J. Mockett,Vladimir I. Klichko,Svetlana N. Radyuk,Susan K. Legan,Igor Rebrin,William C. Orr

doi:10.1074/jbc.m805832200

Rajindar S. Sohal, Robin J. Mockett + Show 5 more

Open Access

https://doi.org/10.1074/jbc.m805832200

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Abstract

The redox state of tissues tends to become progressively more prooxidizing during the aging process. The hypothesis tested in this study was that enhancement of reductive capacity by overexpression of glucose-6-phosphate dehydrogenase (G6PD), a key enzyme for NADPH biosynthesis, could protect against oxidative stress and extend the life span of transgenic Drosophila melanogaster. Overexpression of G6PD was achieved by combining a UAS-G6PD responder transgene at one of four independent loci with either a broad expression (armadillo-GAL4, Tubulin-GAL4, C23-GAL4, and da-GAL4) or a neuronal driver (D42-GAL4 and Appl-GAL4). The mean life spans of G6PD overexpressor flies were extended, in comparison with driver and responder controls, as follows: armadillo-GAL4 (up to 38%), Tubulin-GAL4 (up to 29%), C23-GAL4 (up to 27%), da-GAL4 (up to 24%), D42-GAL4 (up to 18%), and Appl-GAL4 (up to 16%). The G6PD enzymatic activity was increased, as were the levels of NADPH, NADH, and the GSH/GSSG ratio. Resistance to experimental oxidative stress was enhanced. Furthermore, metabolic rates and fertility were essentially the same in G6PD overexpressors and control flies. Collectively, the results demonstrate that enhancement of the NADPH biosynthetic capability can extend the life span of a relatively long-lived strain of flies, which supports the oxidative stress hypothesis of aging.

Highlights

The concept that maintenance of an optimal redox state is essential to cellular survival is firmly established
We hypothesized that transgenic overexpression of glucose-6-phosphate dehydrogenase (G6PD) in Drosophila melanogaster and the consequent increase in the ability to synthesize NADPH would enhance resistance to oxidative stress and extend the life span of flies
In the presence of the Tubulin-GAL4 driver, each responder line exhibited extension of life span; one of the responder lines was recessive lethal, raising the likelihood of an adverse, insertional position effect, and two of the remaining lines were derived from a single transformant

Summary

The abbreviations used are

Trx-(SH), reduced thioredoxinred; Trx-(S), oxidized thioredoxinox; G6PD, glucose-6-phosphate dehydrogenase; HPLC, high pressure liquid chromatography; RFP, red fluorescent protein; MPA, meta-phosphoric acid. Either there was little effect on longevity, or the life span extensions occurred in genetic backgrounds where life spans of the recipient controls were relatively short. Such effects were not replicated in long-lived backgrounds [14]. In this context, we hypothesized that transgenic overexpression of glucose-6-phosphate dehydrogenase (G6PD) in Drosophila melanogaster and the consequent increase in the ability to synthesize NADPH would enhance resistance to oxidative stress and extend the life span of flies. Results indicate that the life span of Drosophila can be significantly extended by overexpression of G6PD and thereby support the concept that oxidative stress plays a causal role in the aging process

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION