We have previously identified a deletion mutant of human apoB [apoB (Thr26-Tyr27del)] in a subject with primary hypobetalipoproteinemia. The present study determined the effect of Thr26-Tyr27del mutation on apoB secretion using transfected McA-RH7777 cells. Transient or stable transfection of apoB-48 containing the Thr26-Tyr27del mutation showed drastically reduced secretion of the mutant as compared to wild-type apoB-48. No lipoproteins containing the mutant apoB-48 were secreted into the medium. Incubation of transfected cells in a lipid-rich medium in the presence of cycloheximide showed rapid turnover of cell-associated mutant apoB-48 as compared to that of wild-type apoB-48. Immunofluorescence experiments showed that the mutant apoB-48 was mostly localized in the endoplasmic reticulum. Treatment with the proteasomal inhibitor MG132 markedly attenuated the turnover of cell-associated mutant apoB-48, whereas treatment with inhibitors of autophagosomal/lysosomal function (e.g. 3-MA or ammonium chloride) had no effect. Taken together, these results indicated that the defective secretion of the Thr26-Tyr27del mutant was associated with increased intracellular degradation of apoB through the proteasome-dependent pathway.
|Number of pages||9|
|Journal||BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR AND CELL BIOLOGY OF LIPIDS|
|Publication status||Published - 2016|
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology