Redox Control of 20S Proteasome Gating

Laboratório de Bioquímica e Biofísica, Instituto Butantan, São Paulo, Brasil.
Antioxidants & Redox Signaling (Impact Factor: 7.41). 03/2012; 16(11):1183-94. DOI: 10.1089/ars.2011.4210
Source: PubMed


The proteasome is the primary contributor in intracellular proteolysis. Oxidized or unstructured proteins can be degraded via a ubiquitin- and ATP-independent process by the free 20S proteasome (20SPT). The mechanism by which these proteins enter the catalytic chamber is not understood thus far, although the 20SPT gating conformation is considered to be an important barrier to allowing proteins free entrance. We have previously shown that S-glutathiolation of the 20SPT is a post-translational modification affecting the proteasomal activities.
The goal of this work was to investigate the mechanism that regulates 20SPT activity, which includes the identification of the Cys residues prone to S-glutathiolation.
Modulation of 20SPT activity by proteasome gating is at least partially due to the S-glutathiolation of specific Cys residues. The gate was open when the 20SPT was S-glutathiolated, whereas following treatment with high concentrations of dithiothreitol, the gate was closed. S-glutathiolated 20SPT was more effective at degrading both oxidized and partially unfolded proteins than its reduced form. Only 2 out of 28 Cys were observed to be S-glutathiolated in the proteasomal α5 subunit of yeast cells grown to the stationary phase in glucose-containing medium.
We demonstrate a redox post-translational regulatory mechanism controlling 20SPT activity.
S-glutathiolation is a post-translational modification that triggers gate opening and thereby activates the proteolytic activities of free 20SPT. This process appears to be an important regulatory mechanism to intensify the removal of oxidized or unstructured proteins in stressful situations by a process independent of ubiquitination and ATP consumption. Antioxid. Redox Signal. 16, 1183-1194.

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    • "Simultaneously, thiol groups on 26S proteasome subunits are blocked (by dicysteine formation or glutathionylation) and protected from irreversible oxidation or damage. For instance, glutathionylation of cysteine residues on the surface of a-subunits was found to open the 20S channel, thereby activating proteolysis (Silva et al., 2012). In this manner, cysteine modifications may influence ratio of 20S to 26S, as well as their relative activities. "
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    Cell Reports 05/2014; 7(5). DOI:10.1016/j.celrep.2014.04.030 · 8.36 Impact Factor
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    • "Facilitate the opening of the structure of the proteasome,↑ proteasome activities Test tube [127] [128] Synthetic peptidyl alcohols, p-nitroanilides, esters, and nitriles ↑ Proteasome activities Mouse fibroblast cell line [130] Cellular lipid components (e.g., lysophosphatidylinositol, ceramides, and cardiolipin) ↑ Proteasome activities Cells [131] [132] [133] S-glutathionylation Facilitate the opening of the structure of the proteasome,↑ proteasome activities Saccharomyces cerevisiae [134] Oleuropein ↑ Proteasome activities,↑ resistance to oxidative stress,↑ cellular life span Human primary fibroblasts [135] Pollen ↑ Proteasome expression–activities HFL-1 cells [136] Lipid algae extract (Phaeodactylum tricornutum) ↑ Proteasome activity Human keratinocytes [137] 2-Hexyldecanol ↑ Proteasome activity Cells [138] Betullinic acid ↑ CT-L activity Cells [139] Litholcholic acid derivatives ↑ Proteasome activity Cells [140] Curcumin ↑ Proteasome activity Human keratinocytes [141] Natural antioxidants (e.g., 3H-1,2-dithiole-3-thione, sulforaphane) ↑ Proteasome expression Cells [117] [143] ↑ Proteasome expression–activities ↑ Autophagic activities,↑ Nrf2 function Mus musculus [259] [260] Hederagenin and 18α-glycyrrhetinic acid ↑ Proteasome activity Human primary fibroblasts, hBMSCs [151] ↑ Proteasome function Quercetin ↑ CT-L activity HFL-1 cells [112] Zerumbone ↑ Proteasome activity Cells [153] Advanced glycation end products ↑ Expression of immunoproteasome subunits Macrophages [154] Lipopolysaccharide ↑ Immunosubunit expression,↑ CT-L proteasome activity, TNF-α secretion, "
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    • "S-glutathionylation of 20S proteasomal subunits affects mainly alpha subunits as shown predominantly in yeast, directly influencing their gating function and thus proteasomal activity. The residues Cys76 and Cys221 of the α5-subunit of the 20S in yeast were shown to be S-glutathionylated in an ROS-dependent manner, increasing the proteasomal activity via opening of the annulus [21]. The same modification was found in subunits of the 19S regulator: after H2O2-mediated S-glutathionylation of the 26S proteasome, 26S proteasomal activity decreased significantly, while 20S activity remained unchanged [22], as found in isolated samples, as well as in HEK 293-cells and neutrophils. "
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