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PSMB3

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Protein found in humans
PSMB3
Available structures
PDBOrtholog search: PDBe RCSB
List of PDB id codes

4R3O, 4R67, 5A0Q

Identifiers
AliasesPSMB3, HC10-II, proteasome subunit beta 3, proteasome 20S subunit beta 3
External IDsOMIM: 602176; MGI: 1347014; HomoloGene: 2089; GeneCards: PSMB3; OMA:PSMB3 - orthologs
Gene location (Mouse)
Chromosome 11 (mouse)
Chr.Chromosome 11 (mouse)
Chromosome 11 (mouse)Genomic location for PSMB3Genomic location for PSMB3
Band11 D|11 61.07 cMStart97,594,225 bp
End97,604,326 bp
RNA expression pattern
Bgee
HumanMouse (ortholog)
Top expressed in
  • monocyte

  • blood

  • lymph node

  • bone marrow cells

  • right adrenal gland

  • left adrenal gland

  • renal cortex

  • smooth muscle tissue

  • rectum

  • left ventricle
Top expressed in
  • Mesencephalon

  • proximal tubule

  • blastocyst

  • neural tube

  • embryo

  • morula

  • right kidney

  • lens

  • embryo

  • limb
More reference expression data
BioGPS
More reference expression data
Gene ontology
Molecular function
Cellular component
Biological process
Sources:Amigo / QuickGO
Orthologs
SpeciesHumanMouse
Entrez

5691

26446

Ensembl

n/a

ENSMUSG00000069744

UniProt

P49720

Q9R1P1

RefSeq (mRNA)

NM_002795

NM_011971

RefSeq (protein)

NP_002786

NP_036101

Location (UCSC)n/aChr 11: 97.59 – 97.6 Mb
PubMed search
Wikidata
View/Edit HumanView/Edit Mouse

Proteasome subunit beta type-3, also known as 20S proteasome subunit beta-3, is a protein that in humans is encoded by the PSMB3 gene. This protein is one of the 17 essential subunits that contribute to the complete assembly of the 20S proteasome complex. In particular, proteasome subunit beta type-2, along with other beta subunits, assemble into two heptameric rings and subsequently a proteolytic chamber for substrate degradation. The eukaryotic proteasome recognizes degradable proteins, including damaged proteins for protein quality control purpose or key regulatory protein components for dynamic biological processes.

Structure

Protein expression

The gene PSMB3 encodes a member of the proteasome B-type family, also known as the T1B family, that is a 20S core beta subunit. Pseudogenes have been identified on chromosomes 2 and 12. The gene has 6 exons and locates at chromosome band 17q12. The human protein proteasome subunit beta type-3 is 23 kDa in size and composed of 205 amino acids. The calculated theoretical pI of this protein is 6.14.

Complex assembly

The proteasome is a multicatalytic proteinase complex with a highly ordered 20S core structure. This barrel-shaped core structure is composed of 4 axially stacked rings of 28 non-identical subunits: the two end rings are each formed by 7 alpha subunits, and the two central rings are each formed by 7 beta subunits. Three beta subunits (beta1, beta2, and beta5) each contain a proteolytic active site and have distinct substrate preferences. Proteasomes are distributed throughout eukaryotic cells at a high concentration and cleave peptides in an ATP/ubiquitin-dependent process in a non-lysosomal pathway.

Function

Protein functions are supported by its tertiary structure and its interaction with associating partners. As one of 28 subunits of 20S proteasome, protein proteasome subunit beta type-3 contributes to form a proteolytic environment for substrate degradation. Evidences of the crystal structures of isolated 20S proteasome complex demonstrate that the two rings of beta subunits form a proteolytic chamber and maintain all their active sites of proteolysis within the chamber. Concomitantly, the rings of alpha subunits form the entrance for substrates entering the proteolytic chamber. In an inactivated 20S proteasome complex, the gate into the internal proteolytic chamber are guarded by the N-terminal tails of specific alpha-subunit. This unique structure design prevents random encounter between proteolytic active sites and protein substrate, which makes protein degradation a well-regulated process. 20S proteasome complex, by itself, is usually functionally inactive. The proteolytic capacity of 20S core particle (CP) can be activated when CP associates with one or two regulatory particles (RP) on one or both side of alpha rings. These regulatory particles include 19S proteasome complexes, 11S proteasome complex, etc. Following the CP-RP association, the confirmation of certain alpha subunits will change and consequently cause the opening of substrate entrance gate. Besides RPs, the 20S proteasomes can also be effectively activated by other mild chemical treatments, such as exposure to low levels of sodium dodecylsulfate (SDS) or NP-14.

Clinical significance

The proteasome and its subunits are of clinical significance for at least two reasons: (1) a compromised complex assembly or a dysfunctional proteasome can be associated with the underlying pathophysiology of specific diseases, and (2) they can be exploited as drug targets for therapeutic interventions. Recently, more effort has been made to consider the proteasome for the development of novel diagnostic markers and strategies. An improved and comprehensive understanding of the pathophysiology of the proteasome should lead to clinical applications in the future.

The proteasomes form a pivotal component for the ubiquitin–proteasome system (UPS) and corresponding cellular Protein Quality Control (PQC). Protein ubiquitination and subsequent proteolysis and degradation by the proteasome are important mechanisms in the regulation of the cell cycle, cell growth and differentiation, gene transcription, signal transduction and apoptosis. Subsequently, a compromised proteasome complex assembly and function lead to reduced proteolytic activities and the accumulation of damaged or misfolded protein species. Such protein accumulation may contribute to the pathogenesis and phenotypic characteristics in neurodegenerative diseases, cardiovascular diseases, inflammatory responses and autoimmune diseases, and systemic DNA damage responses leading to malignancies.

Several experimental and clinical studies have indicated that aberrations and deregulations of the UPS contribute to the pathogenesis of several neurodegenerative and myodegenerative disorders, including Alzheimer's disease, Parkinson's disease and Pick's disease, Amyotrophic lateral sclerosis (ALS), Huntington's disease, Creutzfeldt–Jakob disease, and motor neuron diseases, polyglutamine (PolyQ) diseases, Muscular dystrophies and several rare forms of neurodegenerative diseases associated with dementia. As part of the ubiquitin–proteasome system (UPS), the proteasome maintains cardiac protein homeostasis and thus plays a significant role in cardiac ischemic injury, ventricular hypertrophy and heart failure. Additionally, evidence is accumulating that the UPS plays an essential role in malignant transformation. UPS proteolysis plays a major role in responses of cancer cells to stimulatory signals that are critical for the development of cancer. Accordingly, gene expression by degradation of transcription factors, such as p53, c-jun, c-Fos, NF-κB, c-Myc, HIF-1α, MATα2, STAT3, sterol-regulated element-binding proteins and androgen receptors are all controlled by the UPS and thus involved in the development of various malignancies. Moreover, the UPS regulates the degradation of tumor suppressor gene products such as adenomatous polyposis coli (APC) in colorectal cancer, retinoblastoma (Rb). and von Hippel–Lindau tumor suppressor (VHL), as well as a number of proto-oncogenes (Raf, Myc, Myb, Rel, Src, Mos, ABL). The UPS is also involved in the regulation of inflammatory responses. This activity is usually attributed to the role of proteasomes in the activation of NF-κB which further regulates the expression of pro inflammatory cytokines such as TNF-α, IL-β, IL-8, adhesion molecules (ICAM-1, VCAM-1, P-selectin) and prostaglandins and nitric oxide (NO). Additionally, the UPS also plays a role in inflammatory responses as regulators of leukocyte proliferation, mainly through proteolysis of cyclines and the degradation of CDK inhibitors. Lastly, autoimmune disease patients with SLE, Sjögren syndrome and rheumatoid arthritis (RA) predominantly exhibit circulating proteasomes which can be applied as clinical biomarkers.

Interactions

PSMB3 has been shown to interact with PLK1.

References

  1. ^ GRCm38: Ensembl release 89: ENSMUSG00000069744Ensembl, May 2017
  2. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  3. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. Nothwang HG, Tamura T, Tanaka K, Ichihara A (Oct 1994). "Sequence analyses and inter-species comparisons of three novel human proteasomal subunits, HsN3, HsC7-I and HsC10-II, confine potential proteolytic active-site residues". Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression. 1219 (2): 361–8. doi:10.1016/0167-4781(94)90060-4. PMID 7918633.
  5. Alongside alpha subunits 1-7, constitutive beta subunits 1-7, and inducible subunits including beta1i, beta2i, beta5i
  6. "Entrez Gene: PSMB3 proteasome (prosome, macropain) subunit, beta type, 3".
  7. Coux O, Tanaka K, Goldberg AL (1996). "Structure and functions of the 20S and 26S proteasomes". Annual Review of Biochemistry. 65: 801–47. doi:10.1146/annurev.bi.65.070196.004101. PMID 8811196.
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  28. Powell SR (Jul 2006). "The ubiquitin–proteasome system in cardiac physiology and pathology". American Journal of Physiology. Heart and Circulatory Physiology. 291 (1): H1 – H19. doi:10.1152/ajpheart.00062.2006. PMID 16501026. S2CID 7073263.
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Further reading

PDB gallery
  • 1iru: Crystal Structure of the mammalian 20S proteasome at 2.75 A resolution 1iru: Crystal Structure of the mammalian 20S proteasome at 2.75 A resolution
Proteasome endopeptidase complex subunits (EC 3.4.25.1)
A (alpha subunits)
B (beta subunits)
C (ATPases)
D (non-ATPases)
E (activator subunits)
F (inhibitor subunit)
Category: