Expression of the human apolipoprotein E gene in cultured mammalian cells

C. A. Reardon, Y. F. Lau, Y. K. Paik, K. H. Weisgraber, R. W. Mahley, J. M. Taylor

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Abstract

The gene for human apolipoprotein (apo-) E was isolated from a human genomic library constructed in the cosmid shuttle vector pCV108. The transient expression of the apo-E gene was examined in cultured mammalian cells 48 h following calcium phosphate-mediated gene transfer. The expression of the cloned human apo-E gene, which contained between 0.7 and 29 kilobases of 5'-flanking DNA, was not restricted to human cells or to cultured cells derived from tissues that have been shown to synthesize apo-E. Several independent mouse L cell stable transfectants with the human apo-E gene integrated into their genome were selected on the basis of G418 resistance, which is conferred by the selectable gene marker in the cosmid vector. The levels of human apo-E mRNA found in the stable transfected mouse L cells ranged from undetectable to a level comparable to that found in the human liver. The size of the apo-E mRNA observed in the stable transfectants was identical to that found in the liver, indicating that the mouse L cells were capable of correctly processing the human apo-E gene transcripts. The integrated human apo-E genes had not undergone major rearrangements or deletions during transfer, and the level of apo-E mRNA found in the different stable transfectants correlated directly with the number of integrated copies of the human apo-E gene. The stable transfected L cells secreted authentic human apo-E into the medium. The secreted protein interacted specifically with antibodies to human plasma apo-E and had a apparent M(r) = 35,000 to 36,000, which is slightly larger than that of plasma apo-E. The secreted human apo-E was associated with lipid (presumably phospholipids), floated at d ~ 1.09 g/ml, and bound with high affinity to the apo-B,E(LDL) receptor on fibroblasts.

Original languageEnglish
Pages (from-to)9858-9864
Number of pages7
JournalJournal of Biological Chemistry
Volume261
Issue number21
Publication statusPublished - 1986

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Reardon, C. A., Lau, Y. F., Paik, Y. K., Weisgraber, K. H., Mahley, R. W., & Taylor, J. M. (1986). Expression of the human apolipoprotein E gene in cultured mammalian cells. Journal of Biological Chemistry, 261(21), 9858-9864.