Impairment of proteasome-associated deubiquitinating enzyme Uchl5/UBH-4 affects autophagy

The autophagy-lysosomal pathway (ALP) and the ubiquitin-proteasome system (UPS) are the two major intracellular proteolytic systems that mediate protein turnover in eukaryotes. Although a crosstalk exists between these two systems, it is still unclear how UPS and ALP interact in vivo . Here, we have investigated how impaired function of the proteasome-associated deubiquitinating enzyme (DUB) Uchl5/UBH-4, a regulator of proteasome activity, affects autophagy in human cells and in various tissues in a multicellular organism. We have used the established GFP-LC3-RFP-LC3ΔG autophagy reporter HeLa cell line and show that downregulation of Uchl5 by siRNA reduces autophagy, which is similar to a previously reported role of the proteasome-associated DUB Usp14 on autophagy. Exposing Caenorhabditis elegans carrying the autophagy reporter mCherry::GFP::LGG-1 to ubh-4 or usp-14 RNAi, or to their pharmacological inhibitors, results in diverse effects regarding the numbers of autophagosomes and autolysosomes in the intestine, hypodermal seam cells and the pharynx. Our results reveal that the proteasome-associated DUBs Uchl5/UBH-4 and Usp14 affect autophagy in a differential tissue manner. A deeper insight into the interplay between UPS and ALP in various tissues in vivo has the potential to promote development of therapeutic approaches for disorders associated with proteostasis dysfunction.