Charge‐mediated proteasome targeting

Abstract

A majority of thousands of intracellular mammalian proteins are recognized by proteasome only being conjugated with ubiquitin (Ub), representing a universal degradation signal operated by the ubiquitination system. Ub‐independent proteasome targeting is rationalized by the existence of 2 types of direct proteasome signals (DPSs), specific amino acid sequences or post‐translational modifications, which are recognized by proteasome regulatory subunits. Historically, the first type was shown to exist in ornithine decarboxylase, whereas acetylation of core histones recently was reported as a second type of DPS. Here we declare a third type, representing charge‐mediated DPS. This discovered DPS may be classified as a monopartite composition‐ but not sequence‐dependent element of ∼70 Å in length enriched in basic and flexible amino acids. This type of degradation signal, which may be provided by cationic chemicals, is most efficiently engaged by proteasomes capped with regulator (REG)α or REGγ in an ATP‐independent manner. Taken together, our findings suggest a novel modality of proteasome‐substrate interrelation bypassing ubiquitination.—Kudriaeva, A., Kuzina, E. S., Zubenko, O., Smirnov, I. V., Belogurov, A. Charge‐mediated proteasome targeting. FASEB J. 33, 6852–6866 (2019). http://www.fasebj.org

Exploring the proteasome system: A novel concept of proteasome inhibition and regulation

“…In vitro data support the notion that PA28αβ functions as a molecular sieve to regulate hydrophilicity of peptides generated by proteasomal cleavage in order to improve production of MHC I compatible antigenic peptides . A recent study suggests that PA28αβ proteasome complexes might degrade specific substrates that contain a novel charge-dependent degradation signal enriched in basic and flexible amino acids (Kudriaeva, Kuzina, Zubenko, Smirnov, & Belogurov, 2019). In cells, PA28αβ not only binds to the 20S particle but also to 26S proteasomes and possibly regulates the subcellular localization of 26S proteasome complexes (Cascio, Call, Petre, Walz, & Goldberg, 2002).…”

Protein electrostatics: From computational and structural analysis to discovery of functional fingerprints and biotechnological design

“…Recently, Kudriaeva and co-workers [9] characterized the myelin basic protein (MBP) DPS, showing that it is enriched in basic and flexible amino acids and its signaling function is charge-mediated. Notably, MBP mutants with negative or less positive surface charge showed a decrease in proteasomal degradation rate in vitro .…”

Polyamines Counteract Carbonate-Driven Proteasome Stalling in Alkaline Conditions

“…The proteasome samples were prepared according to the protocol described in [33]. A bovine liver was mechanically homogenized in a hypotonic lysis buffer containing 10 mM Tris-HCl (pH 7.9), 1.5 mM MgCl 2 , 1 mM ATP, and 10 mM KCl.…”

“…Previously, it was shown that polyamines may increase the activity of enzymes, such as α-chymotrypsin [31], and act like chemical chaperones [32]. In contrast, proteins enriched with basic amino acids such as arginine and lysine may directly bind proteasomes [33,34] and are capable of further translocation into the proteolytic chamber [35,36]. Here, we investigate how the alkalization and increased concentration of polyamines may modulate the activity of proteasome, a part of the ubiquitin proteasome system (UPS), which specifically degrades thousands of intracellular proteins.…”