Mitochondrial chaperone TRAP1 activates the mitochondrial UPR and extends healthspan in Drosophila

Abstract

The molecular mechanisms influencing healthspan are unclear but mitochondrial function, resistance to oxidative stress and proteostasis are recurring themes. Tumor necrosis factor Receptor Associated Protein 1 (TRAP1), the mitochondrial analogue of Hsp75, regulates levels of reactive oxygen species in vitro and is found expressed at higher levels in tumor cells where it is thought to play a pro-survival role. While TRAP1-directed compartmentalized protein folding is a promising target for cancer therapy, its role at the organismal level is unclear. Here we report that overexpression of TRAP1 in Drosophila extends healthspan by enhancing stress resistance, locomotor activity and fertility while depletion of TRAP1 has the opposite effect, with little effect on lifespan under both conditions. In addition, modulating TRAP1 expression promotes the nuclear translocation of homeobox protein Dve and increases expression of genes associated with the mitochondrial unfolded protein response (UPRmt), indicating an activation of this proteostasis pathway. Notably, independent genetic knockdown of components of the UPRmt pathway dampen the enhanced stress resistance observed in TRAP1 overexpression flies. Together these studies suggest that TRAP1 regulates healthspan, potentially through activation of the UPRmt.

Drosophila melanogaster mitochondrial Hsp22: a role in resistance to oxidative stress, aging and the mitochondrial unfolding protein response

“…*p \ 0.05, and ****p \ 0.0001. b Whole fly protein extracts from a where separated on 12 % SDS polyacrylamide gel (SDS-PAGE) and transferred onto nitrocellulose membrane (Morrow et al 2004b). Western blots were made with anti-Hsp22 (#36, 1/5000, (Morrow et al 2000)), anti-Hsp60 (#37 1/5000, (Laplante et al 1998)), anti-mtHsp70 (#JLD3, 1/5000, (Carbajal et al 1993)), and a peroxidaseconjugated goat-anti-rabbit secondary antibody ortholog of ClpX) and CG5045 (the ortholog of ClpP) (Baqri et al 2014;Owusu-Ansah et al 2008). The way by which the signal is transduced from the mitochondria to the nucleus has not been investigated in details, but one study has shown an increased translocation of the transcription factor DVE (ortholog of C. elegans DVE-1) to the nucleus in conditions of mitochondrial stress, a situation similar to worms UPR MT (Baqri et al 2014).…”

“…Western blots were made with anti-Hsp22 (#36, 1/5000, (Morrow et al 2000)), anti-Hsp60 (#37 1/5000, (Laplante et al 1998)), anti-mtHsp70 (#JLD3, 1/5000, (Carbajal et al 1993)), and a peroxidaseconjugated goat-anti-rabbit secondary antibody ortholog of ClpX) and CG5045 (the ortholog of ClpP) (Baqri et al 2014;Owusu-Ansah et al 2008). The way by which the signal is transduced from the mitochondria to the nucleus has not been investigated in details, but one study has shown an increased translocation of the transcription factor DVE (ortholog of C. elegans DVE-1) to the nucleus in conditions of mitochondrial stress, a situation similar to worms UPR MT (Baqri et al 2014). However, another group has shown that part of the flies UPR MT is driven by the c-Jun Nterminal kinase (JNK) pathway through activation of jun-related antigen (Jra also known as Djun, the fly ortholog of c-Jun), which is similar to mammalian UPR MT (Hill and Van Remmen 2014;Owusu-Ansah et al 2008).…”

“…Moreover, while the anti-mtHsp70 recognizes mainly the mitochondrial form of Hsp70, it recognizes also the nuclear form (Carbajal et al 1993). Finally, the involvement of TRAP1 in the flies UPR MT has been suggested from studies using flies over-expressing the chaperone or carrying mutations preventing its expression but no direct measurements of its mRNA or protein levels upon UPR MT induction have yet been reported (Baqri et al 2014).…”

“…In fact some aspects of the UPR MT are limited by the nature of the stress, the age and the sex of the animal (Tower 2014). Accordingly, flies UPR MT driven by TRAP1 is different in males and females due partly to differences in bioenergetics between both sexes Baqri et al 2014).…”

“…Among mitochondrial chaperones, Hsp60/Hsp10 and mitochondrial Hsp70 (mtHsp70) have been associated with UPR MT in different organisms. In Drosophila melanogaster, two other mitochondrial chaperones are involved in this important stress response, namely Hsp22 and tumor necrosis factor receptor associated protein 1 (TRAP1) (Baqri et al 2014;Shen and Tower 2013;Tower 2014;Tower et al 2014). While TRAP1 is a member of the HSP90 family of chaperone, Hsp22 is a small heat shock protein (sHSP) that is preferentially up-regulated during aging.…”