Determinants of human apolipoprotein [a] secretion from mouse hepatocyte cultures

Jin Wang, Jennifer Boedeker, Helen H. Hobbs, Ann L. White

Research output: Contribution to journalArticle

10 Scopus citations

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 languageEnglish (US)
Pages (from-to)60-69
Number of pages10
JournalJournal of lipid research
Volume42
Issue number1
StatePublished - Feb 21 2001

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Keywords

  • Apolipoprotein B
  • Endoplasmic reticulum
  • Lipoprotein [a]
  • Proteasome
  • Transcription
  • Transformed liver cell lines

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology
  • Cell Biology

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