An Allosteric Interaction Network Promotes Conformation State-Dependent Eviction of the Nas6 Assembly Chaperone from Nascent 26S Proteasomes

Nemec, Antonia A.; Peterson, Anna K.; Warnock, Jennifer L.; Reed, Randi G.; Tomko, Robert J.

doi:10.1016/j.celrep.2018.12.042

Cited by 17 publications

(50 citation statements)

References 61 publications

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“…Despite their lower degradation activity, Rpn5-VTENKIF mutant proteasomes show an elevated ATPase rate in the absence of substrate that increases in response to substrate processing, albeit to a lesser extent than for wild type (Figure 1—figure supplement 1D). In agreement with recent findings (Nemec et al, 2019), proteasomes containing the Rpn5-VTENKIF mutation more strongly retained the Nas6 assembly chaperone during holoenzyme reconstitution (Figure 1—figure supplement 1E). However, this presence of Nas6 is not the main cause for the observed decrease in degradation rate, as purified endogenous proteasomes from S. cerevisiae carrying the same Rpn5 mutations also exhibit major deficiencies in single-turnover degradation reactions (Figure 1C), despite containing only negligible amounts of Nas6 (Figure 1—figure supplement 1F).…”

Section: Resultssupporting

confidence: 92%

Specific lid-base contacts in the 26s proteasome control the conformational switching required for substrate degradation

Greene

Goodall

Peña

et al. 2019

eLife

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The 26S proteasome is essential for proteostasis and the regulation of vital processes through ATP-dependent degradation of ubiquitinated substrates. To accomplish the multi-step degradation process, the proteasome’s regulatory particle, consisting of lid and base subcomplexes, undergoes major conformational changes whose origin is unknown. Investigating the Saccharomyces cerevisiae proteasome, we found that peripheral interactions between the lid subunit Rpn5 and the base AAA+ ATPase ring are important for stabilizing the substrate-engagement-competent state and coordinating the conformational switch to processing states upon substrate engagement. Disrupting these interactions perturbs the conformational equilibrium and interferes with degradation initiation, while later processing steps remain unaffected. Similar defects in early degradation steps are observed when eliminating hydrolysis in the ATPase subunit Rpt6, whose nucleotide state seems to control proteasome conformational transitions. These results provide important insight into interaction networks that coordinate conformational changes with various stages of degradation, and how modulators of conformational equilibria may influence substrate turnover.

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Section: Resultssupporting

confidence: 92%

Specific lid-base contacts in the 26s proteasome control the conformational switching required for substrate degradation

Greene

Goodall

Peña

et al. 2019

eLife

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“…Despite their lower degradation activity, Rpn5-VTENKIF mutant proteasomes show an elevated ATPase rate in the absence of substrate that increases in response to substrate processing, albeit to a lesser extent than for wild type (Supplemental Figure 1D). In agreement with recent findings (27), proteasomes containing the Rpn5-VTENKIF mutation more strongly retained the Nas6 assembly chaperone during holoenzyme reconstitution. However, this presence of Nas6 is not responsible for the observed decrease in degradation rate, as purified endogenous proteasomes from S. cerevisiae carrying the same Rpn5 mutations are similarly deficient in degradation, but contain negligible amounts of bound Nas6 ( Figure 1C; Supplemental Figure 1E).…”

Section: Figure 1: the Proteasome Lid Subcomplex Is Required For Protsupporting

confidence: 93%

Specific lid-base contacts in the 26S proteasome control the conformational switching required for substrate engagement and degradation

et al. 2019

Preprint

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The 26S proteasome is essential for protein homeostasis and the regulation of vital cellular processes through ATP-dependent degradation of ubiquitinated substrates. To accomplish the multi-step reaction of protein degradation, the proteasome's regulatory particle, consisting of the lid and base subcomplexes, undergoes major conformational changes whose origin and control are largely unknown. Investigating the Saccharomyces cerevisiae 26S proteasome, we found that peripheral interactions between the lid subunit Rpn5 and the base AAA+ ATPase ring play critical roles in stabilizing the substrateengagement-competent state and coordinating the conformational switch to processing states after a substrate has been engaged. Disrupting these interactions perturbs the conformational equilibrium and interferes with degradation initiation, while later steps of substrate processing remain unaffected. Similar defects in the early degradation steps are also observed when eliminating hydrolysis in the ATPase subunit Rpt6, whose nucleotide state seems to control conformational transitions of the proteasome. These results provide important insight into the network of interactions that coordinate conformational changes with various stages of proteasomal degradation, and how modulators of conformational equilibria may influence substrate turnover.

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“…The base appears to exploit ATP-dependent conformational changes in the Rpt subunits to evict the chaperones and allow stable RP-CP association (Roelofs et al, 2009; Park et al, 2013). This mechanism was recently described in detail for Nas6 (Nemec et al, 2019); upon lid-base association, interaction of Rpn5 with the base promotes an ATP-dependent conformational change in Rpt3 that drives release of Nas6 from the nascent proteasome.…”

Section: Regulated Assembly Of the Proteasome Regulatory Particlementioning

confidence: 87%

Dynamic Regulation of the 26S Proteasome: From Synthesis to Degradation

Marshall

Vierstra

2019

Front. Mol. Biosci.

181

178

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All eukaryotes rely on selective proteolysis to control the abundance of key regulatory proteins and maintain a healthy and properly functioning proteome. Most of this turnover is catalyzed by the 26S proteasome, an intricate, multi-subunit proteolytic machine. Proteasomes recognize and degrade proteins first marked with one or more chains of poly-ubiquitin, the addition of which is actuated by hundreds of ligases that individually identify appropriate substrates for ubiquitylation. Subsequent proteasomal digestion is essential and influences a myriad of cellular processes in species as diverse as plants, fungi and humans. Importantly, dysfunction of 26S proteasomes is associated with numerous human pathologies and profoundly impacts crop performance, thus making an understanding of proteasome dynamics critically relevant to almost all facets of human health and nutrition. Given this widespread significance, it is not surprising that sophisticated mechanisms have evolved to tightly regulate 26S proteasome assembly, abundance and activity in response to demand, organismal development and stress. These include controls on transcription and chaperone-mediated assembly, influences on proteasome localization and activity by an assortment of binding proteins and post-translational modifications, and ultimately the removal of excess or damaged particles via autophagy. Intriguingly, the autophagic clearance of damaged 26S proteasomes first involves their modification with ubiquitin, thus connecting ubiquitylation and autophagy as key regulatory events in proteasome quality control. This turnover is also influenced by two distinct biomolecular condensates that coalesce in the cytoplasm, one attracting damaged proteasomes for autophagy, and the other reversibly storing proteasomes during carbon starvation to protect them from autophagic clearance. In this review, we describe the current state of knowledge regarding the dynamic regulation of 26S proteasomes at all stages of their life cycle, illustrating how protein degradation through this proteolytic machine is tightly controlled to ensure optimal growth, development and longevity.

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An Allosteric Interaction Network Promotes Conformation State-Dependent Eviction of the Nas6 Assembly Chaperone from Nascent 26S Proteasomes

Cited by 17 publications

References 61 publications

Specific lid-base contacts in the 26s proteasome control the conformational switching required for substrate degradation

Specific lid-base contacts in the 26s proteasome control the conformational switching required for substrate degradation

Specific lid-base contacts in the 26S proteasome control the conformational switching required for substrate engagement and degradation

Dynamic Regulation of the 26S Proteasome: From Synthesis to Degradation

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