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Calcium increases apolipoprotein B mRNA editing

Z Chen1, T L Eggerman, D Potosky

  • 1National Heart, Lung and Blood Institute, Bethesda, Maryland, 20892, USA.

Biochemical and Biophysical Research Communications
|October 12, 2000
PubMed

Insights

Calcium significantly enhances apolipoprotein B (apoB) mRNA editing in cultured cells, influencing the production of apoB-100 and apoB-48 proteins. This finding reveals a novel role for calcium in regulating gene expression beyond lipid metabolism.

Area of Science:

  • Molecular Biology
  • Lipid Metabolism
  • Gene Regulation

Background:

  • Apolipoprotein B (apoB) mRNA editing generates distinct apoB-100 and apoB-48 proteins, crucial for lipoprotein assembly.
  • Calcium ions are known regulators of very low-density lipoprotein (VLDL) and apoB synthesis and secretion.

Purpose of the Study:

  • To investigate the effect of calcium on apoB mRNA editing.
  • To elucidate the mechanism by which calcium influences apoB mRNA editing.

Main Methods:

  • Utilized cultured human (Caco-2) and rat (McA7777) cell lines.
  • Manipulated extracellular and intracellular calcium concentrations using various agents (e.g., calcium ionophores, thapsigargin).
  • Quantified apoB mRNA editing levels and APOBEC-1 mRNA expression.

Main Results:

  • Increased extracellular calcium concentrations and elevated intracellular calcium levels markedly increased apoB mRNA editing (up to threefold) in a dose-dependent manner.
  • Calcium ionophores (A23187, ionomycin) and thapsigargin treatment enhanced apoB mRNA editing.
  • Calcium did not directly stimulate apoB mRNA editing in an in vitro system, and the effect was independent of APOBEC-1 mRNA expression levels.

Conclusions:

  • Calcium plays a significant role in regulating apoB mRNA editing.
  • The calcium-mediated increase in apoB mRNA editing is likely an intracellular signaling event, not a direct enzymatic effect.
  • These findings expand the known functions of calcium in cellular processes to include post-transcriptional gene regulation of apolipoprotein B.

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