The C-Terminus of the PSMA3 Proteasome Subunit Preferentially Traps Intrinsically Disordered Proteins for Degradation

Biran, Assaf; Myers, Nadav; Steinberger, Shirel; Adler, Julia; Riutin, Marianna; Broennimann, Karin; Reuven, Nina; Shaul, Yosef

doi:10.3390/cells11203231

Cited by 6 publications

(9 citation statements)

References 57 publications

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“…1c ). They can: (i) act like a physical plug, preventing substrate entry to the 20S chamber 21 ; (ii) bind and mask a 20S proteasome substrate-binding site 22 ; (iii) induce allosteric transitions within the 20S proteasome, stabilizing it in an inactive state 23 – 25 . In principle, CCRs may also act at the substrate level, i.e., capturing substrates before they are engaged for degradation.…”

Section: Resultsmentioning

confidence: 99%

Allosteric regulation of the 20S proteasome by the Catalytic Core Regulators (CCRs) family

Deshmukh,

Ben-Nissan,

Olshina

et al. 2023

Nat Commun

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Controlled degradation of proteins is necessary for ensuring their abundance and sustaining a healthy and accurately functioning proteome. One of the degradation routes involves the uncapped 20S proteasome, which cleaves proteins with a partially unfolded region, including those that are damaged or contain intrinsically disordered regions. This degradation route is tightly controlled by a recently discovered family of proteins named Catalytic Core Regulators (CCRs). Here, we show that CCRs function through an allosteric mechanism, coupling the physical binding of the PSMB4 β-subunit with attenuation of the complex’s three proteolytic activities. In addition, by dissecting the structural properties that are required for CCR-like function, we could recapitulate this activity using a designed protein that is half the size of natural CCRs. These data uncover an allosteric path that does not involve the proteasome’s enzymatic subunits but rather propagates through the non-catalytic subunit PSMB4. This way of 20S proteasome-specific attenuation opens avenues for decoupling the 20S and 26S proteasome degradation pathways as well as for developing selective 20S proteasome inhibitors.

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Section: Resultsmentioning

confidence: 99%

Allosteric regulation of the 20S proteasome by the Catalytic Core Regulators (CCRs) family

Deshmukh,

Ben-Nissan,

Olshina

et al. 2023

Nat Commun

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“…Lately, we have reported that the PSMA3 C-terminus (187–255 amino-acids) that we termed “trapper” interacts with many disordered proteins in their degradation [ 9 ]. We employed CRISPR technology to truncate the PSMA3 C-terminal region in the proteasome double-reporter cells, and the pooled cells were subjected to further analysis ( Figure 6 A,B).…”

Section: Resultsmentioning

confidence: 99%

“…Evidence is accumulating for the role of the 20S CP in isolation in degrading proteins [ 9 , 16 , 41 , 42 ]. Since the process is ubiquitin-independent, a key question was how the substrates are recruited for degradation.…”

Section: Discussionmentioning

confidence: 99%

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Method of Monitoring 26S Proteasome in Cells Revealed the Crucial Role of PSMA3 C-Terminus in 26S Integrity

2023

Self Cite

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Proteasomes critically regulate proteostasis via protein degradation. Proteasomes are multi-subunit complexes composed of the 20S proteolytic core particle (20S CP) that, in association with one or two 19S regulatory particles (19S RPs), generates the 26S proteasome, which is the major proteasomal complex in cells. Native gel protocols are used to investigate the 26S/20S ratio. However, a simple method for detecting these proteasome complexes in cells is missing. To this end, using CRISPR technology, we YFP-tagged the endogenous PSMB6 (β1) gene, a 20S CP subunit, and co-tagged endogenous PSMD6 (Rpn7), a 19S RP subunit, with the mScarlet fluorescent protein. We observed the colocalization of the YFP and mScarlet fluorescent proteins in the cells, with higher nuclear accumulation. Nuclear proteasomal granules are formed under osmotic stress, and all were positive for YFP and mScarlet. Previously, we have reported that PSMD1 knockdown, one of the 19 RP subunits, gives rise to a high level of “free” 20S CPs. Intriguingly, under this condition, the 20S-YFP remained nuclear, whereas the PSMD6-mScarlet was mostly in cytoplasm, demonstrating the distinct subcellular distribution of uncapped 20S CPs. Lately, we have shown that the PSMA3 (α7) C-terminus, a 20S CP subunit, binds multiple intrinsically disordered proteins (IDPs). Remarkably, the truncation of the PSMA3 C-terminus is phenotypically reminiscent of PSMD1 knockdown. These data suggest that the PSMA3 C-terminal region is critical for 26S proteasome integrity.

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“…Furthermore, proteins that contain N-terminally disordered regions, such as the human cyclin B1, may be a substrate for both 20S and 26S proteasomes. However, 20S complexes are more efficient than 26S in degrading such a native disordered protein [ 64 ] due to the presence of one of the 20S proteasome subunits, PSMA3, which preferentially interacts and traps IDPs [ 65 ]. Indeed, unmodified cyclin B1, i.e., a Ub-free and intrinsically disordered protein, is readily degraded by the 20S proteasome [ 48 ].…”

Section: Ub-dependent Versus Ub-independent Protein Degradationmentioning

confidence: 99%

Ubiquitin-Dependent and Independent Proteasomal Degradation in Host-Pathogen Interactions

Bialek,

Collawn,

Bartoszewski

2023

Molecules

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Ubiquitin, a small protein, is well known for tagging target proteins through a cascade of enzymatic reactions that lead to protein degradation. The ubiquitin tag, apart from its signaling role, is paramount in destabilizing the modified protein. Here, we explore the complex role of ubiquitin-mediated protein destabilization in the intricate proteolysis process by the 26S proteasome. In addition, the significance of the so-called ubiquitin-independent pathway and the role of the 20S proteasome are considered. Next, we discuss the ubiquitin–proteasome system’s interplay with pathogenic microorganisms and how the microorganisms manipulate this system to establish infection by a range of elaborate pathways to evade or counteract host responses. Finally, we focus on the mechanisms that rely either on (i) hijacking the host and on delivering pathogenic E3 ligases and deubiquitinases that promote the degradation of host proteins, or (ii) counteracting host responses through the stabilization of pathogenic effector proteins.

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The C-Terminus of the PSMA3 Proteasome Subunit Preferentially Traps Intrinsically Disordered Proteins for Degradation

Cited by 6 publications

References 57 publications

Allosteric regulation of the 20S proteasome by the Catalytic Core Regulators (CCRs) family

Allosteric regulation of the 20S proteasome by the Catalytic Core Regulators (CCRs) family

Method of Monitoring 26S Proteasome in Cells Revealed the Crucial Role of PSMA3 C-Terminus in 26S Integrity

Ubiquitin-Dependent and Independent Proteasomal Degradation in Host-Pathogen Interactions

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