Autophagy, an evolutionarily conserved cytoplasmic degradation system, has been implicated as a convergent mechanism in various longevity pathways. Autophagic activity decreases with age in several organisms, but the underlying mechanism is unclear. Here, we show that the expression of Rubicon, a negative regulator of autophagy, increases in aged worm, fly and mouse tissues at transcript and/or protein levels, suggesting that an age-dependent increase in Rubicon impairs autophagy over time, and thereby curtails animal healthspan. Consistent with this idea, knockdown of Rubicon extends worm and fly lifespan and ameliorates several age-associated phenotypes. Tissue-specific experiments reveal that Rubicon knockdown in neurons has the greatest effect on lifespan. Rubicon knockout mice exhibits reductions in interstitial fibrosis in kidney and reduced α-synuclein accumulation in the brain. Rubicon is suppressed in several long-lived worms and calorie restricted mice. Taken together, our results suggest that suppression of autophagic activity by Rubicon is one of signatures of aging.

The accumulation of pathogenic misfolded proteins is believed to be a common mechanism of generation of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and polyglutamine (polyQ) diseases. The autophagy–lysosome degradation system has been considered as a potential therapeutic target against these disorders, as it is able to degrade large protein aggregates. Previously, we focused on Rubicon, a negative regulator of autophagy, and demonstrated that knockdown of the Drosophila homolog of Rubicon (dRubicon) suppressed locomotor dysfunction in a fly model of polyQ disease. This suppression was associated with increased autophagic activity and a marked reduction in the number of polyQ inclusion bodies [1] . We generated transgenic fly lines expressing hemagglutinin-tagged dRubicon wild-type (WT) or dRubicon in which the RUN [after R PIP8 ( R a P 2 i nteracting p rotein 8 ), U NC-14 and N ESCA ( ne w molecule containing S H3 at the ca rboxyl-terminus)] domain was deleted (ΔRUN). We provide data regarding the effect of WT and ΔRUN dRubicon co-expression on polyQ-induced locomotor dysfunction in Drosophila .