Ubiquitinated protein conjugates are specifically enriched in the lysosomal system of fibroblasts

Lajos Laszlo, Fergus J. Doherty, Natasha U. Osborn, R. John Mayer

Research output: Contribution to journalArticle

71 Citations (Scopus)


Ubiquitin-protein conjugates are found by imniunogold electron microscopy to be enriched (12-fold) in the lysosomal compartment of 3T3-L1 fibroblasts. Treatment of fibroblasts with the cysteine protease inhibitor E-64 leads to an expansion of the lysosomal compartment and as a result an increase in the cellular content of ubiquitin-protein conjugates. There is no change in the specific enrichment of ubiquitin-protein conjugates in the lysosomal compartment following E-64 treatment. The results suggest that some ubiquitin-protein conjugates may normally be degraded lysosomally following sequestration by microautophagy and imply that protein ubiquitination may be one of the signals for protein uptake into lysosomes.

Original languageEnglish
Pages (from-to)365-368
Number of pages4
JournalFEBS letters
Issue number2
Publication statusPublished - Feb 26 1990


  • (3T3-L1 fibroblasts)
  • Electron microscopy
  • Epoxysuccinyl-leucylamido-(4-guanadino)butane
  • Lysosome
  • Ubiquitin

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology

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