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A metabolic switch at the center of JNK-induced proteostasis and longevity

ABSTRACT: Aging is associated with a progressive loss of tissue and metabolic homeostasis. Changes in the cellular management of the proteome, as well as changes in cellular metabolism have been implicated in this decline, yet our understanding of causal relationships between these changes remains incomplete. Genetic studies have shown that single-gene perturbations are sufficient to significantly impact the aging process, delaying all associated cellular deficiencies, and thus increasing lifespan. Here, we explore metabolic and proteostatic changes associated with lifespan extension by one such perturbation. Focusing on the Drosophila brain, we comprehensively characterize protein turnover rates and assess metabolic flux to identify changes in protein and metabolic homeostasis in long-lived animals. Using organism-wide 15N labeling, we observe that the turnover rates of ~2000 proteins in the fly head decline with age, and that this decline is prevented in animals with lifespan-extending elevation of Jun-N-terminal Kinase (JNK) activity. Combining transcriptomic, metabolomic, and metabolic flux analysis, we find that JNK activation in the brain results in decreased steady-state Glucose-6-phosphate levels coupled to elevated carbon flux into the pentose phosphate pathway due to the transcriptional induction of Glucose-6-phosphate Dehydrogenase. This metabolic change promotes proteostasis in the aging brain, likely via increased NADPH against oxidative stress response. Through a comprehensive characterization of the cellular and biochemical changes elicited by a lifespan extending mutation, our study thus identifies a JNK-induced metabolic switch that increases lifespan by promoting neuronal proteostasis.

INSTRUMENT(S): TripleTOF 5600

ORGANISM(S): Drosophila Melanogaster (ncbitaxon:7227)

SUBMITTER: Henri Jasper, Brad Gibson, Birgit Schilling

PROVIDER: MSV000080118 | MassIVE |

REPOSITORIES: MassIVE

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Project description:A detailed knowledge of the mechanisms underlying brain aging is fundamental to understand its functional decline and the baseline upon which brain pathologies superimpose. Endogenous protective mechanisms must contribute to the adaptability and plasticity still present in the healthy aged brain. Apolipoprotein D (ApoD) is one of the few genes with a consistent and evolutionarily conserved up-regulation in the aged brain. ApoD protecting roles upon stress or injury are well known, but a study of the effects of ApoD expression in the normal aging process is still missing. Using an ApoD-knockout mouse we analyze the effects of ApoD on factors contributing to the functional maintenance of the aged brain. We focused our cellular and molecular analyses in cortex and hippocampus at an age representing the onset of senescence where mortality risks are below 25%, avoiding bias towards long-lived animals. Lack of ApoD causes a prematurely aged brain without altering lifespan. Age-dependent hyperkinesia and memory deficits are accompanied by differential molecular effects in cortex and hippocampus. Transcriptome analyses reveal distinct effects of ApoD loss on the molecular age-dependent patterns of cortex and hippocampus, with different cell-type contributions to age-regulated gene expression. Markers of glial reactivity, proteostasis, and oxidative and inflammatory damage reveal early signs of aging and enhanced brain deterioration in the ApoD-knockout brain. The lack of ApoD results in an age-enhanced significant reduction in neuronal calcium-dependent functionality markers and signs of early reduction of neuronal numbers in the cortex, thus impinging upon parameters clearly differentiating neurodegenerative conditions from healthy brain aging. Our data support the hypothesis that the physiological increased brain expression of ApoD represents a homeostatic anti-aging mechanism. The brain cortex and hippocampus of young and aged mice of wild-type and ApoD-KO genotypes were used for RNA extraction and hybridization on Affymetrix microarrays. We aim at identifying distinct effects of ApoD loss on the molecular age-dependent patterns of cortex and hippocampus.

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A metabolic switch at the center of JNK-induced proteostasis and longevity

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