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| 26S proteasome | |
|---|---|
| Name | 26S proteasome |
| Organism | Eukaryota |
26S proteasome is a multisubunit eukaryotic protease complex central to intracellular protein quality control, regulated protein turnover, and signal transduction. It functions in ATP-dependent proteolysis, influences cell cycle progression, DNA repair, and antigen presentation, and is conserved across taxa from Saccharomyces cerevisiae to Homo sapiens, shaping responses studied by laboratories at institutions such as Max Planck Society, Howard Hughes Medical Institute, and Cold Spring Harbor Laboratory. Research on the complex intersects with pathways characterized in studies of Andrei Sakharov-era cellular models, clinical work at the National Institutes of Health, and biotechnology platforms from companies like Pfizer and Amgen.
The holoenzyme comprises a 20S core particle capped by one or two 19S regulatory particles, yielding a barrel-shaped proteolytic chamber whose architecture has been resolved by cryo-electron microscopy performed by teams at European Molecular Biology Laboratory, MRC Laboratory of Molecular Biology, and Stanford University; structural models reference homologous assemblies characterized in Thermus thermophilus and Mycobacterium tuberculosis studies. The 20S core is formed by four stacked heptameric rings arranged as α7β7β7α7 with catalytic residues located in β subunits analogous to enzymes studied by researchers at Max Planck Institute for Biochemistry; the 19S particle contains base and lid subcomplexes with six AAA+ ATPases (Rpt1–6) and non-ATPase subunits including Rpn1, Rpn2, Rpn10, and Rpn11 whose arrangement was elucidated in collaborations involving Yale University, University of Oxford, and ETH Zurich. Stoichiometry and paralog variation reflect evolutionary diversification observed in comparative genomic surveys from University of Cambridge and Broad Institute cohorts, and individual subunits are encoded by genes identified in screens by Cold Spring Harbor Laboratory and annotated in databases curated by National Center for Biotechnology Information.
Assembly proceeds via ordered incorporation of subcomplexes facilitated by dedicated chaperones such as p28 and PAC1–PAC4, identified in biochemical purifications carried out at Massachusetts Institute of Technology and University of California, San Francisco; studies employing genetic screens in Drosophila melanogaster and Caenorhabditis elegans defined conserved assembly checkpoints. Maturation includes propeptide processing of β subunits and ATP-dependent conformational transitions mediated by AAA+ motor domains, a sequence of events characterized using pulse-chase assays developed at Johns Hopkins University and in crosslinking mass spectrometry investigations by groups at University of Copenhagen, with regulatory feedback described in reviews from European Research Council-funded consortia.
Substrate engagement often requires polyubiquitin tags attached by E1, E2, and E3 enzymes cataloged in studies at Scripps Research, Columbia University, and The Rockefeller University; ubiquitin receptors in the 19S particle, including Rpn10 and Rpn13, bind chains with linkage preferences delineated by mutational analyses from University of Tokyo and Seoul National University. Deubiquitination by the Rpn11 metalloprotease precedes translocation of unfolded polypeptides through the ATPase ring into the 20S chamber, a translocation mechanism mapped by single-molecule assays from Harvard University and high-resolution cryo-EM by teams at University of California, Berkeley. Proteolysis occurs via N-terminal threonine residues in catalytic β subunits, producing peptide fragments that feed into antigen presentation pathways investigated by immunology groups at Yale School of Medicine and Imperial College London.
Proteasome activity is modulated by phosphorylation, ubiquitination, acetylation, and ADP-ribosylation of subunits documented in phosphoproteomic surveys from European Bioinformatics Institute and mass-spectrometry centers at ProteomeXchange partners; kinases such as casein kinase II and regulatory E3 ligases influence assembly and localization with findings reported from University of Chicago and Karolinska Institutet. Alternate caps such as PA28/11S and PA200 alter substrate selection in contexts studied at Weizmann Institute of Science and Utrecht University, while proteasome inhibitors and activators from pharmaceutical research at Novartis and Celgene demonstrate therapeutic modulation, with activity control also described during oxidative stress responses in reports from University of Milan and Johns Hopkins University.
The complex enforces proteostasis, controls cyclin degradation during cell cycle transitions characterized in landmark studies by Tim Hunt and Paul Nurse-inspired research, and regulates transcription factor turnover implicated in pathways studied at Columbia University and University of Pennsylvania. It participates in DNA damage responses coordinated with ATM kinase and ATR kinase signaling cascades analyzed by investigators at Memorial Sloan Kettering Cancer Center and Dana-Farber Cancer Institute, and it generates peptides for major histocompatibility complex class I presentation central to immunology work at Scripps Research Institute. Roles in development and neuronal proteostasis have been probed in models from Stanford University and Max Planck Institute for Brain Research.
Dysfunction links to cancer, neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, and immune dysregulation documented in clinical and translational studies at Mayo Clinic and Cleveland Clinic. Proteasome inhibitors like bortezomib and carfilzomib, developed through collaborations involving Millennium Pharmaceuticals and Johnson & Johnson, are approved therapies for multiple myeloma and mantle cell lymphoma, while resistance mechanisms have been explored by consortia including European Organisation for Research and Treatment of Cancer and International Myeloma Working Group. Emerging strategies include immunoproteasome-selective inhibitors and proteasome activators pursued in programs at Merck and academic groups at University of Toronto.
Structural studies use cryo-EM, X-ray crystallography, and crosslinking mass spectrometry performed at facilities like Diamond Light Source, Argonne National Laboratory, and EMBL-EBI; biochemical assays exploit fluorogenic peptide substrates, ATPase assays, and ubiquitination assays standardized in protocols from Addgene and core facilities at Broad Institute. Cellular studies employ genetic knockouts via CRISPR–Cas9 developed at Massachusetts Institute of Technology and reporter systems for proteasome activity used in high-throughput screens by groups at Novartis Institutes for BioMedical Research and academic screening centers. Proteasome-targeted chemical probes, activity-based probes, and selective inhibitors are available through collaborations between academic laboratories and biotech firms including Genentech.
Category:Proteasomes