The effect of proteasome inhibitors on mammalian erythroid terminal differentiation.
OBJECTIVE
Murine erythroblasts infected with the anemia-inducing strain of Friend virus (FVA cells) terminally differentiate to the reticulocyte stage after 48 hours of culture in vitro in response to erythropoietin (EPO). The objective of this study was to determine the possible role of proteasome-mediated proteolysis during the terminal differentiation of FVA cells.


METHODS
The proteasome inhibitors MG132 and lactacystin were used to perturb the normal function of proteasomes during terminal differentiation. Effects of proteasome inhibitors on terminal differentiation were quantitated by evaluation of cellular morphology after benzidine staining and by Western blot analyses.


RESULTS
Treatment of EPO-stimulated FVA cells with lactacystin or MG132 at later periods of culture increased accumulations of nuclear and cytosolic ubiquitinated proteins and decreased nuclear extrusion to less than 40% of controls.


CONCLUSIONS
Our results suggest that the proteasomal degradation of ubiquitinated proteins plays an important role in the enucleation of mammalian erythroblasts.
Department of Biotechnical and Clinical Laboratory Sciences, State University of New York at Buffalo, Buffalo, NY, USA
Cheng Yao
CY
Chen
Lynne
L
Pajak
Judith
J
Tamburlin
Diane
D
Bofinger
Stephen T
ST
Koury
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects; D002461:Cell Line, Transformed / Q000187:drug effects / Q000201:enzymology; D002472:Cell Transformation, Viral; D003546:Cysteine Endopeptidases; D003593:Cytoplasm / Q000378:metabolism; D015672:Erythroid Precursor Cells / Q000187:drug effects* / Q000201:enzymology; D004920:Erythropoiesis / Q000187:drug effects*; D005622:Friend murine leukemia virus; D007976:Leupeptins / Q000494:pharmacology*; D051379:Mice; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D009687:Nuclear Proteins / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012156:Reticulocytes / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D025801:Ubiquitin / Q000378:metabolism
D007976:Leupeptins; D009097:Multienzyme Complexes; D009687:Nuclear Proteins; D011480:Protease Inhibitors; D025801:Ubiquitin; C067713:lactacystin; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D000111:Acetylcysteine