Apolipoprotein (apo) B-100 is an essential component of atherogenic plasma lipoproteins. Previous studies have demonstrated that the production of apoB-100 is regulated largely by intracellular degradation at both the co-translational and post-translational levels and that proteasome-mediated and non-proteasome-mediated pathways are involved in this process. ApoB-100 is a glycoprotein. The present study was undertaken to address the question of whether the inhibition of N-linked glycosylation with tunicamycin would interfere with apoB-100 production. We demonstrated that the treatment of HepG2 cells with tunicamycin decreased the net production of apoB-100 by enhancing co-translational degradation of the protein. This effect of tunicamycin was partly prevented by lactacystin, a specific proteasome inhibitor. Because lactacystin only partly reversed the effects of tunicamycin on apoB biogenesis, tunicamycin seemed also to induce apoB co-translational degradation in HepG2 cells by one or more non-proteasomal pathways. Furthermore, tunicamycin increased apoB ubiquitination approx. 4-fold. The proportion of the newly synthesized apoB-100 that was secreted and incorporated into the nascent lipoprotein particles was unaffected by tunicamycin. Thus the tunicamycin-mediated inhibition of N-linked glycosylation interferes with the production of apoB-100 that is mediated by both proteasomal and non-proteasomal pathways.
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February 2001
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Research Article|
January 25 2001
Tunicamycin induces ubiquitination and degradation of apolipoprotein B in HepG2 cells
Wei LIAO
;
Wei LIAO
1Departments of Molecular and Cellular Biology and Medicine, 1 Baylor Plaza, Baylor College of Medicine, Houston, TX 77030-3498, U.S.A.
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Lawrence CHAN
Lawrence CHAN
1
1Departments of Molecular and Cellular Biology and Medicine, 1 Baylor Plaza, Baylor College of Medicine, Houston, TX 77030-3498, U.S.A.
1To whom correspondence should be addressed (e-mail lchan@bcm.tmc.edu).
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Biochem J (2001) 353 (3): 493–501.
Article history
Received:
August 03 2000
Revision Received:
October 25 2000
Accepted:
November 13 2000
Citation
Wei LIAO, Lawrence CHAN; Tunicamycin induces ubiquitination and degradation of apolipoprotein B in HepG2 cells. Biochem J 1 February 2001; 353 (3): 493–501. doi: https://doi.org/10.1042/bj3530493
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