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

Abstract

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-LC3{Delta}G 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. SummaryModulation of UPS via pharmacological or genetic impairment of the proteasome-associated DUB Uchl5/UBH-4 affects autophagy in human cells and in a tissue-differential manner in C. elegans.