PXD061729-1

PXD061729 is an original dataset announced via ProteomeXchange.

Title	Revealing the unexpected interplay between the Proteasome Activator PA200 and the immunoproteasome
Description	The proteasome activator PA200 binds to the catalytic core of the proteasome, the 20S, and activates its proteolytic activities. The cellular function of PA200 is poorly understood and appears to be cell type and differentiation specific. Recent evidence suggests that PA200 not only binds to the standard 20S (s20S) proteasome but also to the specialized immunoproteasome (i20S) which plays a key role in anti-viral and anti-tumor immunity. We here investigated the interaction of PA200 and the immunoproteasome in detail. We show the very first cryo-EM structures of the singly- and doubly-capped i20S-PA200 complexes that revealed no major difference regarding the first binding event of PA200 to the i20S vs. the s20S. However, first PA200 binding triggered a subtle and long-range allosteric bending of the i20S barrel which was not seen in the s20S-PA200 complexes. This resulted in major structural rearrangements in the opposite unbound α ring - the displacement of atoms up to 5.4 Å and the increase in its outer diameter - thereby increasing the occupancy of the second PA200 binding site. Mass photometry confirmed higher occupancy of PA200 to the i20S versus the s20S. Binding of PA200 to the i20S enhanced proteasomal activation compared to the s20S. Co-expression of PA200 and the i20S in cells and tissues, however, is restricted but their interaction is favored upon co-expression. The expression of PA200 and the catalytic subunits of the i20S is differentially regulated depending on the cellular context. Our data also suggest that PA200 has the potential to regulate i20S gene expression whereas the i20S has no effects on PA200 expression. Overall, this work sheds new light on the interaction of PA200 with the i20S from a structural, mechanistic and cellular point of view. Importantly, we identify PA200 as a key regulator of the i20S whenever PA200 and the catalytic subunits of the i20S are co-expressed in the same cell.
HostingRepository	PRIDE
AnnounceDate	2026-06-03
AnnouncementXML	Submission_2026-06-03_12:11:56.204.xml
DigitalObjectIdentifier
ReviewLevel	Peer-reviewed dataset
DatasetOrigin	Original dataset
RepositorySupport	Unsupported dataset by repository
PrimarySubmitter	Julien Marcoux
SpeciesList	scientific name: Homo sapiens (Human); NCBI TaxID: NEWT:9606;
ModificationList	monohydroxylated residue; iodoacetamide derivatized residue
Instrument	timsTOF SCP; Orbitrap Fusion

Revision	Datetime	Status	ChangeLog Entry
0	2025-03-11 19:26:22	ID requested
⏵ 1	2026-06-03 12:11:56	announced

Dataset with its publication pending

submitter keyword: PSME4, LC-MSMS, A549 and H1299 cells, primary human lung fibroblasts,Immunoproteasome

Julien Marcoux
contact affiliation	ProteoToul, Institute of Pharmacology and Structural Biology (IPBS), CNRS, Toulouse
contact email	julien.marcoux@ipbs.fr
lab head
Julien Marcoux
contact affiliation	IPBS
contact email	julien.marcoux@ipbs.fr
dataset submitter

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PRIDE project URI

• PRIDE
  1. PXD061729
     1. Label: PRIDE project
     2. Name: Revealing the unexpected interplay between the Proteasome Activator PA200 and the immunoproteasome