Original Article

Vimentin-dependent utilization of LDL-cholesterol in human adrenal tumor cells is not associated with the level of expression of apoE, sterol carrier protein-2, or caveolin

Correspondence to: Robert M. Evans

SW-13 adrenal tumor cells that lack detectable intermediate filaments (IF-free) exhibit an impaired capacity to esterify lipoprotein-derived cholesterol compared with cells that contain vimentin filaments. IF-free cells were found to synthesize and secrete significant amounts of apoE, while apoE secretion was nearly undetectable in cell lines that spontaneously express vimentin. However, stable transfectants that express a mouse vimentin cDNA exhibited elevated levels of cholesterol esterification and apoE secretion compared with untransfected IF-free cells, indicating that apoE secretion is not directly related to the capacity of these cells to esterify cholesterol. Some of the cell lines that differed in the level of apoE synthesis and secretion had similar levels of apoE mRNA, suggesting that the differences in expression involve a post-transcriptional mechanism. Treatment of these cells with forskolin and IBMX, 8br-cAMP, or TPA had no effect on apoE secretion. The level of sterol carrier protein-2 (SCP₂) synthesis and the distribution of SCP₂ between membrane and soluble cellular fractions was not observably different in cells that contained or lacked vimentin. SW-13 cell lines contained little or no detectable caveolin-1 or caveolin-2.

These studies demonstrate that the difference in the capacity of these adrenal tumor cells that contain or lack vimentin filaments to esterify low density lipoprotein-cholesterol is not obviously associated with the level of expression or distribution of apoE, SCP₂, or caveolins.—Holwell, T. A., S. C. Schweitzer, M. E. Reyland, and R. M. Evans. Vimentin-dependent utilization of LDL-cholesterol in human adrenal tumor cells is not associated with the level of expression of apoE, sterol carrier protein-2, or caveolin. J. Lipid Res. 1999. 40: 1440;–1452.

Supplementary key words: apolipoprotein E, sterol carrier protein-2, caveolins, cholesterol esterification, vimentin, intermediate filaments, adrenal cortical cells

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