The three main protein degradation pathways in the cell are the proteasome, the lysosome and autophagy. Autophagy is a general term for processes by which cytoplasmic materials including organelles reach lysosomes for degradation. Ubiquitin-E3 ligases are the components of the ubiquitin machinery that confer specificity to the ubiquitination process by recognizing target substrates and mediating transfer of ubiquitin from an E2 ubiquitin-conjugating enzyme to the substrate. The RING finger E3 ligase RNF-5 is an ER-bound protein implicated in ER-associated degradation (ERAD). Using the LGG-1/LC3::GFP reporter [1] we revealed that RNF-5 inhibition caused an increase in autophagy . Our purpose is to understand the mechanism by which RNF-5 regulates autophagy.
rnf-5(
tm794) mutant worms are more resistant to ER stress than wild-type animals, as assessed by exposing them to tunicamycin, an inhibitor of N-glycosylation. This resistance was reduced when different components of the autophagy core machinery were knocked down, suggesting that the activity of RNF-5 in the regulation of ER homeostasis is mediated through autophagy. Life span analysis revealed that elevated levels of RNF-5 in
eat-2(
ad465) mutant worms, but not in wild-type worms, suppressed their longevity phenotype. Since autophagy is required for the longevity of
eat-2 worms [2, 3], we conclude that elevated expression of RNF-5 reduced autophagy in these animals and diminished their longevity. Together these data suggest that RNF-5 is a negative regulator of autophagy.
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