Yeast PI31 inhibits the proteasome by a direct multisite mechanism

Rawson, Shaun; Walsh, Richard M.; Velez, Benjamin; Schnell, Helena M.; Jiao, Fenglong; Blickling, Marie; Ang, Jessie; Bhanu, Meera K.; Huang, Lan; Hanna, John

doi:10.1038/s41594-022-00808-5

Cited by 13 publications

(49 citation statements)

References 55 publications

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“…1 ), indicating that binding occurs symmetrically and specifically. Interestingly, the observed peptide-like densities share some similarities with a recently published yeast 20S structure containing the proteasome inhibitor PI31 10 . Using the yeast version of PI31 as a starting point, we utilized a combination of motif searches and structural homology searches to identify divergent PI31-like proteins in microsporidians (Supplementary Fig.…”

Section: Resultssupporting

confidence: 76%

“…The β-subunits are shown as surfaces colored as in ( a ), with the active-site threonine highlighted in yellow and PI31L as red cartoon with selected residues as sticks. The yeast PI31 structure (PDB-7TEO 10 [ https://www.rcsb.org/structure/7TEO ]) is superimposed and shown in shades of green. e A schematic representation of proteolytic active sites and specificity sites, with active site threonines shown in yellow and PI31 orientations shown in red ( V. necatrix ) or green ( S. cerevisiae ).…”

Section: Resultsmentioning

confidence: 99%

“…For example, when carbon is limiting, proteasomes reversibly accumulate in cytoplasmic puncta known as proteasome storage granules (PSGs) 7 , which are thought to act as a reservoir from which proteasomes can be efficiently recovered once carbon is plentiful 8 . In other cases, proteasomes are inactivated through interactions with inhibitory proteins 9 , 10 .…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly, structural characterizations of the complex required the use of a mutated strain lacking the α3 subunit due to the low occupancy of PI31 in wild-type proteasomes. This mutation leads to the incorporation of two α4 subunits per alpha ring, and results in an aberrantly opened 20S gate conformation 10 , 14 . The increased interactions with open or incorrectly folded proteasomes suggest that PI31 may recognize and inhibit CPs with dysfunctional conformations in yeast 10 .…”

Section: Introductionmentioning

confidence: 99%

“…This mutation leads to the incorporation of two α4 subunits per alpha ring, and results in an aberrantly opened 20S gate conformation 10 , 14 . The increased interactions with open or incorrectly folded proteasomes suggest that PI31 may recognize and inhibit CPs with dysfunctional conformations in yeast 10 . It is unclear, however, whether PI31 plays a role outside of interactions with defective proteasomes, and if this function and mechanism are conserved across eukaryotes.…”

Section: Introductionmentioning

confidence: 99%

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Structure of the reduced microsporidian proteasome bound by PI31-like peptides in dormant spores

et al. 2022

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Proteasomes play an essential role in the life cycle of intracellular pathogens with extracellular stages by ensuring proteostasis in environments with limited resources. In microsporidia, divergent parasites with extraordinarily streamlined genomes, the proteasome complexity and structure are unknown, which limits our understanding of how these unique pathogens adapt and compact essential eukaryotic complexes. We present cryo-electron microscopy structures of the microsporidian 20S and 26S proteasome isolated from dormant or germinated Vairimorpha necatrix spores. The discovery of PI31-like peptides, known to inhibit proteasome activity, bound simultaneously to all six active sites within the central cavity of the dormant spore proteasome, suggests reduced activity in the environmental stage. In contrast, the absence of the PI31-like peptides and the existence of 26S particles post-germination in the presence of ATP indicates that proteasomes are reactivated in nutrient-rich conditions. Structural and phylogenetic analyses reveal that microsporidian proteasomes have undergone extensive reductive evolution, lost at least two regulatory proteins, and compacted nearly every subunit. The highly derived structure of the microsporidian proteasome, and the minimized version of PI31 presented here, reinforce the feasibility of the development of specific inhibitors and provide insight into the unique evolution and biology of these medically and economically important pathogens.

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Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 99%