The Lysine 48 and Lysine 63 Ubiquitin Conjugates Are Processed Differently by the 26 S Proteasome
Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, USA. Journal of Biological Chemistry
(Impact Factor: 4.57).
10/2009; 284(51):35485-94. DOI: 10.1074/jbc.M109.052928
The role of Lys-63 ubiquitin chains in targeting proteins for proteasomal degradation is still obscure. We systematically compared proteasomal processing of Lys-63 ubiquitin chains with that of the canonical proteolytic signal, Lys-48 ubiquitin chains. Quantitative mass spectrometric analysis of ubiquitin chains in HeLa cells determines that the levels of Lys-63 ubiquitin chains are insensitive to short-time proteasome inhibition. Also, the Lys-48/Lys-63 ratio in the 26 S proteasome-bound fraction is 1.7-fold more than that in the cell lysates, likely because some cellular Lys-63 ubiquitin conjugates are sequestered by Lys-63 chain-specific binding proteins. In vitro, Lys-48 and Lys-63 ubiquitin chains bind the 26 S proteasome comparably, whereas Lys-63 chains are deubiquitinated 6-fold faster than Lys-48 chains. Also, Lys-63 tetraubiquitin-conjugated UbcH10 is rapidly deubiquitinated into the monoubiquitinated form, whereas Lys-48 tetraubiquitin targets UbcH10 for degradation. Furthermore, we found that both the ubiquitin aldehyde- and 1,10-phenanthroline-sensitive deubiquitinating activities of the 26 S proteasome contribute to Lys-48- and Lys-63-linkage deubiquitination, albeit the inhibitory extents are different. Together, our findings suggest that compared with Lys-48 chains, cellular Lys-63 chains have less proteasomal accessibility, and proteasome-bound Lys-63 chains are more rapidly deubiquitinated, which could cause inefficient degradation of Lys-63 conjugates.
Available from: Selvaraju Karthik
- "In contrast to POH1, USP14 and UCHL5 share a different mode of action and preferentially cleave ubiquitin from the distal ends of ubiquitin chains leading to progressive chain shortening the recycling of ubiquitin back into the UPS. USP14 preferentially cleaves Lys48-linked polyubiquitin chains (Hanna et al., 2006; Hu et al., 2005), whereas UCHL5 appears to be more promiscuous, cleaving both Lys48-and Lys63-linkage types (Jacobson et al., 2009). Interestingly, USP14 appears to hinder proteasome degradation by actively trimming ubiquitin chains on target proteins resulting in prolonged occupancy at the 19S RP and potentially favouring release back to the cytosol (Hanna et al., 2006; Lee et al., 2010, 2011b). "
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ABSTRACT: Although more traditionally associated with degradation and maintenance of protein homeostasis, the ubiquitin-proteasome system (UPS) has emerged as a critical component in the regulation of cancer cell growth and survival. The development of inhibitors that block the proteolytic activities of the proteasome have highlighted its suitability as a bona fide anti-cancer drug target. However, key determinants including the development of drug resistance and dose-limiting toxicity call for the identification of alternative components of the UPS for novel drug targeting. Recently the deubiquitinases (DUBs), a diverse family of enzymes that catalyze ubiquitin removal, have attracted significant interest as targets for the development of next generation UPS inhibitors. In particular, pharmacological inhibition of the proteasomal cysteine DUBs (i.e., USP14 and UCHL5) has been shown to be particularly cytotoxic to cancer cells and inhibit tumour growth in several in vivo models. In the current review we focus on the modes of action of proteasome DUB inhibitors and discus the potential of DUB inhibitors to circumvent acquired drug resistance and provide a therapeutic option for the treatment of cancer.
Copyright © 2015 Elsevier Ltd. All rights reserved.
Drug resistance updates: reviews and commentaries in antimicrobial and anticancer chemotherapy 07/2015; 21-22. DOI:10.1016/j.drup.2015.06.001 · 9.12 Impact Factor
Available from: Ignacio Marin
- "E3 function regulates protein degradation, Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/developmentalbiology apoptosis, signaling, protein trafficking, and transcription (Hershko and Ciechanover, 1998; Jacobson et al., 2009; Komander, 2009). E3 ubiquitin ligases are grouped into two major classes: HECT (Homologous to the E6-AP Carboxyl Terminus)-domain and RING (Really Interesting New Gene)-finger E3 ligases (Ardley and Robinson , 2005; Kipreos, 2005; Metzger et al., 2012). "
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ABSTRACT: E3 ubiquitin ligases constitute a large family of enzymes that modify specific proteins by covalently attaching ubiquitin polypeptides. This post-translational modification can serve to regulate protein function or longevity. In spite of their importance in cell physiology, the biological roles of most ubiquitin ligases remain poorly understood. Here, we analyzed the function of the HECT domain family of E3 ubiquitin ligases in stem cell biology and tissue regeneration in planarians. Using bioinformatic searches, we identified 17 HECT E3 genes that are expressed in the Schmidtea mediterranea genome. Whole-mount in situ hybridization experiments showed that HECT genes were expressed in diverse tissues and most were expressed in the stem cell population (neoblasts) or in their progeny. To investigate the function of all HECT E3 ligases, we inhibited their expression using RNA interference (RNAi) and determined that orthologs of huwe1, wwp1, and trip12 had roles in tissue regeneration. We show that huwe1 RNAi knockdown led to a significant expansion of the neoblast population and death by lysis. Further, our experiments showed that wwp1 was necessary for both neoblast and intestinal tissue homeostasis as well as uncovered an unexpected role of trip12 in posterior tissue specification. Taken together, our data provide insights into the roles of HECT E3 ligases in tissue regeneration and demonstrate that planarians will be a useful model to evaluate the functions of E3 ubiquitin ligases in stem cell regulation.
Copyright © 2015. Published by Elsevier Inc.
Developmental Biology 05/2015; 404(2). DOI:10.1016/j.ydbio.2015.04.021 · 3.55 Impact Factor
Available from: Henry Lauris Paulson
- "Although all possible linkage types are present in cells, their precise functions remain only partially understood (Xu et al., 2009). Chains formed through the addition of ubiquitin exclusively at lysine 48 (K48) have been recognized to signal protein degradation (Glickman and Ciechanover, 2002), whereas K63-linked ubiquitin chains seem to subserve diverse functions beyond protein degradation (Jacobson et al., 2009). For example, K63-linked chains regulate NF-κB signaling not by promoting protein degradation but by influencing ubiquitin-dependent protein-protein interactions (Hadian et al., 2011). "
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ABSTRACT: Control of proper protein synthesis, function, and turnover is essential for the health of all cells. In neurons these demands take on the additional importance of supporting and regulating the highly dynamic connections between neurons that are necessary for cognitive function, learning, and memory. Regulating multiple unique synaptic protein environments within a single neuron while maintaining cell health requires the highly regulated processes of ubiquitination and degradation of ubiquitinated proteins through the proteasome. In this review, we examine the effects of dysregulated ubiquitination and protein clearance on the handling of disease-associated proteins and neuronal health in the most common neurodegenerative diseases.
Frontiers in Molecular Neuroscience 07/2014; 7:63. DOI:10.3389/fnmol.2014.00063 · 4.08 Impact Factor
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