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Dynamic association of proteasomal machinery with the centrosome.

Although the number of pathologies known to arise from the inappropriate folding of proteins continues to grow, mechanisms underlying the recognition and ultimate disposition of misfolded polypeptides remain obscure. For example, how and where such substrates are identified and processed is unknown. We report here the identification of a specific subcellular structure in which, under basal conditions, the 20S proteasome, the PA700 and PA28 (700- and 180-kD proteasome activator complexes, respectively), ubiquitin, Hsp70 and Hsp90 (70- and 90-kD heat shock protein, respectively) concentrate in HEK 293 and HeLa cells. The structure is perinuclear, surrounded by endoplasmic reticulum, adjacent to the Golgi, and colocalizes with gamma-tubulin, an established centrosomal marker. Density gradient fractions containing purified centrosomes are enriched in proteasomal components and cell stress chaperones. The centrosome-associated structure enlarges in response to inhibition of proteasome activity and the level of misfolded proteins. For example, folding mutants of CFTR form large inclusions which arise from the centrosome upon inhibition of proteasome activity. At high levels of misfolded protein, the structure not only expands but also extensively recruits the cytosolic pools of ubiquitin, Hsp70, PA700, PA28, and the 20S proteasome. Thus, the centrosome may act as a scaffold, which concentrates and recruits the systems which act as censors and modulators of the balance between folding, aggregation, and degradation.

Pubmed ID: 10225950 RIS Download

Mesh terms: Adenosine Triphosphatases | Animals | Centrosome | Chickens | Cysteine Endopeptidases | Cystic Fibrosis Transmembrane Conductance Regulator | Fetus | Gene Expression Regulation, Enzymologic | HSP70 Heat-Shock Proteins | HeLa Cells | Humans | Kidney | Multienzyme Complexes | Mutagenesis | Proteasome Endopeptidase Complex | Protein Folding | Tubulin

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Associated grants

  • Agency: NIDDK NIH HHS, Id: R01 DK046181
  • Agency: NIDDK NIH HHS, Id: R01 DK049835
  • Agency: NIDCR NIH HHS, Id: DE12309
  • Agency: NIDDK NIH HHS, Id: R56 DK046181
  • Agency: NIDDK NIH HHS, Id: DK49835
  • Agency: NIDCR NIH HHS, Id: R01 DE012309
  • Agency: NIDDK NIH HHS, Id: R37 DK049835
  • Agency: NIDDK NIH HHS, Id: R01 DK038938
  • Agency: NIDDK NIH HHS, Id: DK46181

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