Inhibition of cholesteryl ester formation in human fibroblasts by an analogue of 7-ketocholesterol and by progesterone

Goldstein, Joseph L.; Faust, Jerry R.; Dygos, John H.; Chorvat, Robert J.; Brown, M.

doi:10.1073/pnas.75.4.1877

Cited by 71 publications

(21 citation statements)

References 16 publications

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“…Additionally, preputial gland size in both male and female rats is increased by progesterone, while estrogen stimulates lipid synthesis, including that of sterol esters, in female rat preputial gland cells (42). At this point we do not know how steroid hormone administration affects mouse ACAT mRNA levels in vivo, but progesterone has been shown to inhibit ACAT activity in cultured fibroblasts (43), rabbit ovary (44), and rat liver microsomes (14,45). Thus it is possible that ACAT expression is steroid hormone-responsive in vivo and that hormonal regulation of ACAT is involved in the development of certain specialized cells such as the sebocyte.…”

Section: Figmentioning

confidence: 94%

Tissue-specific Expression and Cholesterol Regulation of Acylcoenzyme A:Cholesterol Acyltransferase (ACAT) in Mice

Uelmen

Oka

Sullivan

et al. 1995

Journal of Biological Chemistry

118

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The 3.7-kilobase cDNA clone isolated contains a 1620-base pair open reading frame which encodes a protein of 540 amino acids. The predicted mouse ACAT protein is 87% identical to the protein product of human ACAT K1 and shares many of the same secondary structural features, including two transmembrane domains, a leucine heptad motif consistent with dimer or multimer formation, and five regions homologous to the "signature sequences" found in other enzymes that catalyze acyl adenylation followed by acyl thioester formation and acyl transfer. Using the cDNA as a hybridization probe, we mapped the gene encoding mouse ACAT to chromosome 1 in a region syntenic to human chromosome 1 where the ACAT gene is located. Northern blot analysis and RNase protection assays of mouse tissues revealed that ACAT mRNA is expressed most highly in the adrenal gland, ovary, and preputial gland and is least abundant in skeletal muscle, adipose tissue, heart, and brain. To study the dietary regulation of ACAT mRNA expression in mouse tissues, we fed C57BL/6J mice a high-fat, highcholesterol (HF/HC) atherogenic diet for 3 weeks and measured ACAT mRNA levels in various tissues by RNase protection. The HF/HC diet had little effect on ACAT mRNA levels in the small intestine, aorta, adrenal, or peritoneal macrophages, whereas hepatic ACAT mRNA levels were doubled in mice fed the atherogenic diet. ACAT activity in liver microsomes was similarly increased in cholesterol-fed mice, suggesting that mouse ACAT is regulated at least in part at the level of mRNA abundance. Additionally, a significant positive correlation was observed between ACAT activity and microsomal free cholesterol levels in chow-and cholesterol-fed mice, supporting the concept of cholesterol availability as a regulator of ACAT. To further investigate the regulation of ACAT activity under controlled conditions, ACAT-deficient Chinese hamster ovary cells were stably transfected with the mouse ACAT cDNA clone driven by a cytomegalovirus promoter. Two transfected Chinese hamster ovary cell lines that expressed the mouse ACAT transgene regained the ability to esterify cholesterol. Cholesterol esterification activity in both of these cell lines was further increased by exposure of these cells to low density lipoprotein. Thus we have demonstrated that mouse ACAT expression in vivo and in vitro is regulated by at least two mechanisms: control of mRNA abundance and post-transcriptional regulation of the enzyme activity, probably by cholesterol availability.The process of cholesterol homeostasis in extrahepatic tissues such as the fibroblast involves the uptake of lipoproteins by cell surface receptors, lysosomal hydrolysis of lipoproteinderived cholesteryl esters to yield free cholesterol, and reesterification of free cholesterol in the endoplasmic reticulum for storage in cytoplasmic lipid droplets. The re-esterification step is crucial to prevent excess free cholesterol from disrupting cell membranes and is carried out by the enzyme acyl-CoA: cholesterol acyltransferase (ACAT) 1 (for...

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Section: Figmentioning

confidence: 94%

Tissue-specific Expression and Cholesterol Regulation of Acylcoenzyme A:Cholesterol Acyltransferase (ACAT) in Mice

Uelmen

Oka

Sullivan

et al. 1995

Journal of Biological Chemistry

118

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“…In addition, cholesterol esterification in vitro varies with the availability of cholesterol to the undersaturated enzyme (3,25,26). Furthermore, a parallel has been demonstrated between the rate of cholesterol esterification in vivo and that in the corresponding unfractionated membranes from cells treated with LDL (6), acetylated LDL (27), progesterone (28), or oxysterols such as 25-HC (6,29). While these results are consistent with the premise that in vitro esterification manifests the pool of cholesterol in the ER, other mechanisms could obscure this relationship.…”

mentioning

confidence: 99%

Quantitation of the Pool of Cholesterol Associated with Acyl-CoA:Cholesterol Acyltransferase in Human Fibroblasts

Lange

Steck

1997

Journal of Biological Chemistry

113

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“…Chloroquine also prevented the activation of ACAT by VLDL (Table 1). These findings indicate that VLDL are degraded in the lysosomes similar to LDL degradation in human skin fibroblasts (Goldstein et al, 1978). The experiments with preadipocytes from human fat tissue showed that these cells bind and metabolize LDL more efficiently than VLDL.…”

Section: Resultsmentioning

confidence: 55%

“…The results shown in Table 2 indicate that the rat preadipocytes bind, internalize, and degrade human VLDL nearly three times more than human LDL. To investigate the involvement oflysosomal degradation in the metabolism of lipoproteins in these cells, the effect of chloroquine, which is known to inhibit the lysosomal enzymes by increasing the intralysosomal pH, was studied (Goldstein et al, 1978). When After the preadipocytes were incubated with medium containing LPDS for 48 h, the medium was removed and replaced with fresh medium.…”

Section: Resultsmentioning

confidence: 99%

“…The binding of 1251-labelled LDL and VLDL was studied at 4 'C for 3 h. After incubation, the monolayers were washed three times using phosphate-buffered saline containing bovine serum albumin and three times using the same buffer without albumin and then dissolved in 0.2 M-NaOH, and the radioactivity was determined. To study the degradation of the lipoproteins, the cells were incubated with 1251-labelled LDL and VLDL at 37 'C for 5 h. The medium was collected, and the trichloroacetic acidsoluble non-iodide radioactivity was determined as described elsewhere (Goldstein et al, 1977). In the same experiment, the cell-associated radioactivity was determined after extensive washing of the monolayers.…”

Section: Binding and Degradation Of Lipoproteins In Preadipocytesmentioning

confidence: 99%

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Metabolism of apolipoprotein E-containing human plasma lipoproteins by rat and human cells in culture

Ranganathan¹,

Matsuura²,

Yamamoto³

et al. 1986

Biochemical Journal

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Cultured preadipocytes from rat epididymal fat pads were able to bind, internalize, and degrade human plasma very-low-density lipoproteins (VLDL) more efficiently than low-density lipoproteins (LDL). VLDL, but not LDL, activated acyl-CoA: cholesterol acyltransferase (ACAT) and increased cholesterol accumulation in these cells. However, trypsin-treated VLDL (T-VLDL) lost the capacity to bind, activate ACAT, and increase cholesterol accumulation. After the treatment of VLDL with trypsin, SDS/polyacrylamide-gel electrophoresis and immunoblotting showed that apolipoprotein E (apo E) was completely degraded, whereas apolipoprotein CII (apo C-II) was preserved. ApoE complexed with dimyristoyl phosphatidylcholine (DMPC) was able to complete with VLDL for binding to the cells. Although T-VLDL did not bind to the preadipocytes, these cells accumulate triacylglycerols from T-VLDL, presumably after lipolysis, as efficiently as from native VLDL. Rat smooth muscle cells and skin fibroblasts also bind and metabolize human VLDL better than LDL. However, human skin fibroblasts and omental preadipocytes metabolized LDL better than VLDL. These studies indicate that rat tissues can recognize and metabolize apoE-containing human plasma VLDL although they cannot recognize human LDL.

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Inhibition of cholesteryl ester formation in human fibroblasts by an analogue of 7-ketocholesterol and by progesterone

Abstract: The synthesis of cholesteryl esters in cultured human fibroblasts is catalyzed by a microsomal acyl-coenzyme A:cholesterol acyltransferase (EC 2.3.1.26

Cited by 71 publications

References 16 publications

Tissue-specific Expression and Cholesterol Regulation of Acylcoenzyme A:Cholesterol Acyltransferase (ACAT) in Mice

Tissue-specific Expression and Cholesterol Regulation of Acylcoenzyme A:Cholesterol Acyltransferase (ACAT) in Mice

Quantitation of the Pool of Cholesterol Associated with Acyl-CoA:Cholesterol Acyltransferase in Human Fibroblasts

Metabolism of apolipoprotein E-containing human plasma lipoproteins by rat and human cells in culture

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