Linked Life Data

15328361

Source:http://linkedlifedata.com/resource/pubmed/id/15328361

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
45
pubmed:dateCreated
2004-11-1
pubmed:abstractText
The degradation of cellular proteins by proteasomes generates peptides 2-24 residues long, which are hydrolyzed rapidly to amino acids. To define the final steps in this pathway and the responsible peptidases, we fractionated by size the peptides generated by proteasomes from beta-[14C]casein and studied in HeLa cell extracts the degradation of the 9-17 residue fraction and also of synthetic deca- and dodecapeptide libraries, because peptides of this size serve as precursors to MHC class I antigenic peptides. Their hydrolysis was followed by measuring the generation of smaller peptides or of new amino groups using fluorescamine. The 14C-labeled peptides released by 20 S proteasomes could not be degraded further by proteasomes. However, their degradation in the extracts and that of the peptide libraries was completely blocked by o-phenanthroline and thus required metallopeptidases. One such endopeptidase, thimet oligopeptidase (TOP), which was recently shown to degrade many antigenic precursors in the cytosol, was found to play a major role in degrading proteasome products. Inhibition or immunodepletion of TOP decreased their degradation and that of the peptide libraries by 30-50%. Pure TOP failed to degrade proteasome products 18-24 residues long but degraded the 9-17 residue fraction to peptides of 6-9 residues. When aminopeptidases in the cell extract were inhibited with bestatin, the 9-17 residue proteasome products were also converted to peptides of 6-9 residues, instead of smaller products. Accordingly, the cytosolic aminopeptidase, leucine aminopeptidase, could not degrade the 9-17 residue fraction but hydrolyzed the peptides generated by TOP to smaller products, recapitulating the process in cell extracts. Inactivation of both TOP and aminopeptidases blocked the degradation of proteasome products and peptide libraries nearly completely. Thus, degradation of most 9-17 residue proteasome products is initiated by endoproteolytic cleavages, primarily by TOP, and the resulting 6-9 residue fragments are further digested to amino acids by aminopeptidases.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
5
pubmed:volume
279
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
46723-32
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed-meshheading:15328361-Aminopeptidases, pubmed-meshheading:15328361-Antigens, pubmed-meshheading:15328361-Caseins, pubmed-meshheading:15328361-Catalysis, pubmed-meshheading:15328361-Chromatography, pubmed-meshheading:15328361-Chromatography, High Pressure Liquid, pubmed-meshheading:15328361-Cytosol, pubmed-meshheading:15328361-Endopeptidases, pubmed-meshheading:15328361-Gene Library, pubmed-meshheading:15328361-HeLa Cells, pubmed-meshheading:15328361-Humans, pubmed-meshheading:15328361-Hydrolysis, pubmed-meshheading:15328361-Leucyl Aminopeptidase, pubmed-meshheading:15328361-Metalloendopeptidases, pubmed-meshheading:15328361-Peptides, pubmed-meshheading:15328361-Protease Inhibitors, pubmed-meshheading:15328361-Proteasome Endopeptidase Complex, pubmed-meshheading:15328361-Protein Structure, Tertiary, pubmed-meshheading:15328361-Time Factors
pubmed:year
2004
pubmed:articleTitle
Pathway for degradation of peptides generated by proteasomes: a key role for thimet oligopeptidase and other metallopeptidases.
pubmed:affiliation
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.