Ubiquitinated protein conjugates are specifically enriched in the lysosomal system of fibroblasts.
Ubiquitin-protein conjugates are found by immunogold 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.
Laszlo
L
L
Department of General Zoology, ELTE University, Budapest, Hungary.
Doherty
F J
FJ
Osborn
N U
NU
Mayer
R J
RJ
D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors; D005347:Fibroblasts / Q000648:ultrastructure*; D007150:Immunohistochemistry; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D008854:Microscopy, Electron; D011506:Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D014452:Ubiquitins / Q000235:genetics / Q000378:metabolism*
D015853:Cysteine Proteinase Inhibitors; D011506:Proteins; D012333:RNA, Messenger; D014452:Ubiquitins; D007770:L-Lactate Dehydrogenase; D007930:Leucine; C024974:E 64