Abstract
Efforts to develop an in vitro model system to analyze apolipoprotein [a] (apo[a]) gene transcription, mRNA translation, and protein secretion have been complicated by the limited tissue and species distribution of apo[a] and the presence of regulatory DNA sequences remote from the apo[a] transcription start site. In the current study we examined primary hepatocytes cultured from apo[a] transgenic mice as a model system for analyzing apo[a] biogenesis. Hepatocytes from mice transgenic for a yeast artificial chromosome (YAC) encoding the entire apo[a] gene in its own genomic context (YAC-apo[a] hepatocytes) were unable to maintain apo[a] expression beyond 48 h of culture. Tiffs suggests that the apo[a] promoter was not active in cultured YAC-apo[a] hepatocytes. In contrast, apo[a] expression was maintained for at least 7 days in hepatocytes cultured from mice transgenic for an apo[a] cDNA under control of the mouse transferrin promoter (transferrin-apo[a] hepatocytes). Pulse-chase experiments established that more than 80% of apo[a] synthesized by both transferrin-apo[a] and YAC-apo[a] hepatocytes was degraded prior to secretion, independently of the coexpression of human apoB. Thus, low secretion efficiency appears to be a general characteristic of human apo[a] proteins in mouse liver. Apo[a] secretion was increased somewhat (from 18% to 32%) in the presence of lipoprotein-containing serum. Transformed cell lines derived from transferrin apo[a] hepatocytes retained characteristics of apo[a] secretion similar to those observed in primary cells. Primary and transformed apo[a] transgenic hepatocytes may provide valuable additional models with which to study posttranslational mechanisms regulating apo[a] secretion.
Original language | English (US) |
---|---|
Pages (from-to) | 60-69 |
Number of pages | 10 |
Journal | Journal of lipid research |
Volume | 42 |
Issue number | 1 |
State | Published - 2001 |
Keywords
- Apolipoprotein B
- Endoplasmic reticulum
- Lipoprotein [a]
- Proteasome
- Transcription
- Transformed liver cell lines
ASJC Scopus subject areas
- Biochemistry
- Endocrinology
- Cell Biology