Intracellular degradation of newly synthesized apolipoprotein (apo) B can occur at every
stage of the secretory pathway, from the protein translation, polypeptide translocation across
the membrane of endoplasmic reticulum (ER), to vesicular transport. The prevalence of
apoB degradation at each stage varies in different hepatic cell systems examined.
Proteolysis of nascent apoB can be catalyzed by the ubiquitin-proteasome system in the
cytosol, and probably by unidentified ER resident proteases as well. Cytosolic and ER …