JNK/FOXO-mediated Neuronal Expression of Fly Homologue of Peroxiredoxin II Reduces Oxidative Stress and Extends Life Span

Abstract

Activation of c-Jun N-terminal kinase (JNK) signaling in neurons increases stress resistance and extends life span, in part through FOXO-mediated transcription in Drosophila. However, the JNK/ FOXO target genes are unknown. Here, we identified Jafrac1, a Drosophila homolog of human Peroxiredoxin II (hPrxII), as a downstream effecter of JNK/FOXO signaling in neurons that enhances stress resistance and extends life span. We found that Jafrac1 was expressed in the adult brain and induced by paraquat, a reactive oxygen species-generating chemical. RNA interference-mediated neuronal knockdown of Jafrac1 enhanced, while neuronal overexpression of Jafrac1 and hPrxII suppressed, paraquat-induced lethality in flies. Neuronal expression of Jafrac1 also significantly reduced ROS levels, restored mitochondrial function, and attenuated JNK activation caused by paraquat. Activation of JNK/FOXO signaling in neurons increased the Jafrac1 expression level under both normal and oxidative stressed conditions. Moreover, neuronal knockdown of Jafrac1 shortened, while overexpression of Jafrac1 and hPrxII extended, the life span in flies. These results support the hypothesis that JNK/FOXO signaling extends life span via amelioration of oxidative damage and mitochondrial dysfunction in neurons.FOXO transcription factors are key regulators of growth, metabolism, life span, and stress resistance in various organisms, including Drosophila (1, 2). FOXO is regulated by the insulin signaling pathway and the stress-induced JNK 4 signaling pathway (3, 4). Oxidative stress activates the stress-responsive JNK, which promotes FOXO nuclear localization and upregulates expression of antioxidant proteins (5, 6).In Drosophila, neuronal activation of JNK/FOXO signaling confers resistance to oxidative stress and extends life span (4, 7). Neurons are particularly susceptible to oxidative damage because of their high levels of ROS production and relatively low levels of antioxidant enzymes (8). Thus, activation of the JNK/FOXO pathway in neurons may extend life span through up-regulation of anti-oxidative stress genes. However, little is known regarding the JNK/FOXO target genes in neurons.Thiol-reducing systems are important reducers of many oxidative stressors, such as peroxide (9). Peroxiredoxin (Prx), also called thioredoxin peroxidase, eliminates hydroperoxide with thioredoxin as an immediate hydrogen donor and reduces ROS levels (10). Among six distinct mammalian Prxs (I-VI), Prx II is exclusively expressed in the brain (11), suggesting that Prx II may play an important role in response to oxidative stress in neurons. However, the regulation of PrxII expression in neurons has not been elucidated. In this study, we demonstrated that neuronal expression of Jafrac1, a Drosophila homologue of human Prx II (hPrxII), was regulated by JNK/FOXO signaling, promoted resistance to oxidative stress, and extended the life span of the flies. EXPERIMENTAL PROCEDURESDrosophila Culture and Mutants-Drosophila melanogaster were kept at 25°C and cultured using standar...

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“…PRXs have recently been shown to participate in signal transduction pathways that regulate resistance to oxidative stress and lifespan extension through regulation of JNK/FOXO signaling in Drosophila melanogaster (48). We did not observe an increase in chondrocyte JNK phosphorylation in response to menadione-induced oxidative stress but rather found increased phosphorylation of MMK-3/6 and p38 along with inhibition of IGF-1-mediated Akt activation.…”

A Novel MitoTimer Reporter Gene for Mitochondrial Content, Structure, Stress, and Damage in Vivo

“…Paraquat was dissolved in water at 100 mM and added to 5% sucrose at 10 mM. These two drugs were administered to adult flies (20 days old) 24 h after 6 h of fasting as described by Lee et al (24). Rotenone was first dissolved in dimethyl sulfoxide at 4 mM, added to freshly made fly food at 60°C at 0.4 mM, and used to feed the flies for 4 days after 6 h of fasting (25).…”

Peroxiredoxins, gerontogenes linking aging to genome instability and cancer

“…Prx deficiency results in accelerated aging in yeast, worms, flies, and rodents (Neumann et al 2003;Olahova et al 2008;Lee et al 2009;Timmermann et al 2010). Moreover, the yeast and rat Prxs, Tsa1 and PrxII, are becoming increasingly hyperoxidized during aging in the absence of external peroxide stress (Musicco et al 2009;Molin et al 2011), indicating that Prx inactivation may be a common phenomenon in different aging organisms.…”

“…For example, a neuronal Prx, Jafrac1, in Drosophila acts as a downstream effector of the nutrient-responsive transcription factor FOXO in life span extension (Lee et al 2009). Likewise, the major cytosolic Prx of budding yeast, Tsa1, and its repair enzyme, the sulfiredoxin (Srx) Srx1, are downstream targets for nutrient-responsive (RAS-PKA) signaling, and bolstering their activity extends life span .…”