Post-translational modification of cardiac proteasomes: functional delineation enabled by proteomics

Abstract

Proteasomes are ubiquitously expressed multicatalytic complexes that serve as key regulators of protein homeostasis. There are several lines of evidence indicating that proteasomes exist in heterogeneous subpopulations in cardiac muscle, differentiated, in part, by post-translational modifications (PTMs). PTMs regulate numerous facets of proteasome function, including catalytic activities, complex assembly, interactions with associating partners, subcellular localization, substrate preference, and complex turnover. Classical technologies used to identify PTMs on proteasomes have lacked the ability to determine site specificity, quantify stoichiometry, and perform large-scale, multi-PTM analysis. Recent advancements in proteomic technologies have largely overcome these limitations. We present here a discussion on the importance of PTMs in modulating proteasome function in cardiac physiology and pathophysiology, followed by the presentation of a state-of-the-art proteomic workflow for identifying and quantifying PTMs of cardiac proteasomes.

The Amazing Ubiquitin-Proteasome System: Structural Components and Implication in Aging

“…The proteasome functionality is also regulated by posttranslational modifications although the effect(s) of these modifications on proteasome activity remain still unclear (Bose et al, 2004;Kikuchi et al, 2010;Scruggs et al, 2012;Zong et al, 2008). Specifically, it was found that several proteasome subunits can be phosphorylated in vivo (e.g., the a2-a4, a7, and the Rpt2, Rpt6 subunits) (Feng et al, 2001;Iwafune et al, 2002Iwafune et al, , 2004Mason et al, 1996).…”

The Path to Personalized Cardiovascular Medicine

“…303,304 As advanced MS-based proteomic technologies enable identification various protein PTMs, recent phosphoproteome studies have identified numerous regulatory phosphorylation events in cardiomyocytes, cardiac myofilaments, cardiac mitochondria and 20S proteosomes. [305][306][307][308][309][310] Other types of PTMs, such as O-GlcNAc, which has emerged as essential regulators of cardiovascular physiology and pathophysiology and heart aging, have also been detected. 268,[311][312][313] AP-MS approach as a powerful tool to characterize protein interactome has identified cardiac protein kinase C ε (PKCε)-containing multiprotein complexes.…”

“…In addition to deciphering subunit composition, multiple PTMs of subunits, which regulate complex assembly, catalytic characteristics, subcellular localization and turnover, essential for cardiac health and disease, have been identified. 310 Metabolomics represents the global profiling of low molecular weight (typically <2 kDa) biochemicals, such as amino and organic acids, nucleotides, carbohydrates, lipids and more, in an organism, tissue or cell. Although the size of the human metabolome, which comprises ~3-5 × 10 3 endogenous metabolites, is much smaller than the human genome, transcriptome or proteome, we are just starting to explore this powerful tool in searching for novel biomarkers and gaining insights into cardiovascular health and disease.…”

Characterizing the Dynamics of Proteasome Complexes by Proteomics Approaches

“…Such strategies have proved to be powerful and effective, and they have been successfully applied to unravel the molecular details of the UPS. For example, a series of proteomic studies have been carried out to map PTMs of proteasomes (55,66), define the contents of ubiquitomes (43,83), elucidate protein complex composition and structure, and decipher interaction landscapes of various protein complexes such as deubiquitinases, E3 ubiquitin ligases, and proteasomes (6,8,19,31,33,38,42,48,70,77,80,81). The vast amount of information gained by proteomics studies has dramatically enhanced our current understanding of the UPS on a more systems level.…”