Studies on the assembly of apolipoprotein B-100- and B-48-containing very low density lipoproteins in McA-RH7777 cells.

摘要: The mechanisms by which apolipoprotein B-100 (apoB-100) and apoB-48 assemble lipoproteins have been studied in the McA-RH7777 cell line. After incubation for 2 h with 360 microM oleic acid, cells secreted apoB-100 mainly on very low density lipoprotein (VLDL) particles, as judged from sucrose gradient sequential ultracentrifugation. ApoB-48 was both VLDL denser, high (HDL)-like lipoproteins. Both occurred particles luminal content of total microsomal fraction. In addition, proteins were present denser particular, those that banded HDL region. containing cells, whereas retained degraded. Pulse-chase experiments showed secretory pathway already after a labeling period short 3 min. Thus, this particle first apoB-100-containing could be detected fraction cell. assembly labeled acutely (within min) completely blocked cycloheximide, if cycloheximide added pulse period. If, other hand, 15-min chase introduced period, there no effect VLDL. A is enough to allow pulse-labeled apoB nascent polypeptides completed apoB-100. These results indicated dependent upon ongoing protein biosynthesis during time when polypeptide elongate. secretion are independent biosynthesis. apoB-48-containing seen HDL-like particle. well different lengths radioactive formation delayed compared also relation including 30-min [35S]methionine followed 120-min depleted almost all except particle.(ABSTRACT TRUNCATED AT 400 WORDS)