Transport of Cholesterol into Mitochondria Is Rate-limiting for Bile Acid Synthesis via the Alternative Pathway in Primary Rat Hepatocytes

Pandak, William M.; Ren, Shuling; Marques, Dalila; Hall, Elizabeth A. H.; Redford, Kaye; Mallonee, D H; Bohdan, Patricia; Heuman, Douglas M.; Gil, Gregorio; Hylemon, Phillip B.

doi:10.1074/jbc.m205244200

Cited by 117 publications

(107 citation statements)

References 28 publications

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“…Adenovirus DNA from the resulting plaques was further screened by analytical digestions for the presence of the insert. To purify the recombinant virus, the crude supernatant was carefully layered over a two-step CsCl gradient as described (24). For the mouse experiments, a control virus was used that contained the LacZ sequence.…”

Section: Methodsmentioning

confidence: 99%

The Role of α1-Fetoprotein Transcription Factor/LRH-1 in Bile Acid Biosynthesis

Castillo-Olivares

Campos

Pandak

et al. 2004

Journal of Biological Chemistry

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Two key regulatory enzymes in the bile acid biosynthesis pathway are cholesterol 7␣-hydroxylase/CYP7A1 (7␣-hydroxylase) and sterol 12␣-hydroxylase/CYP8B1 (12␣-hydroxylase). It has been shown previously that hepatocyte nuclear factor-4␣ (HNF-4) and the ␣ 1 -fetoprotein transcription factor (FTF) are activators of 7␣-and 12␣-hydroxylase transcription and that the small heterodimer partner (SHP) suppresses bile acid biosynthesis by heterodimerizing with FTF. However, the role of FTF in bile acid biosynthesis has been studied only in tissue culture systems. In heterozygous FTF knockout mice, 7␣-and 12␣-hydroxylase genes were expressed at 5-7-fold higher levels than in wild-type mice, an apparent direct contradiction to previous in vitro observations. This higher expression of the 7␣-and 12␣-hydroxylase genes resulted in a 33% higher bile acid pool in their gallbladders, bile more enriched in cholic acid, and a 13% decrease in plasma cholesterol levels. Adenovirusmediated FTF overexpression in wild-type mice resulted in 10-fold lower expression of the 7␣-and 12␣-hydroxylase genes and up to 8-fold higher SHP expression, highlighting the dual role that FTF plays in different promoters. Shorter overexpression times still resulted in lower 7␣-and 12␣-hydroxylase expression, but unchanged SHP expression, suggesting that two different mechanisms are involved in the FTF-mediated suppression of 7␣-and 12␣-hydroxylase expression. This FTF-mediated suppression of the expression of two bile acid biosynthesis genes resulted in a 3-fold lower rate of bile acid synthesis in a rat bile fistula animal model. Based on these observations and on protein binding studies performed in vitro and by chromatin immunoprecipitation, we hypothesize that FTF has two synergetic effects that contribute to its role in bile acid biosynthesis: 1) it has the ability to activate the expression of SHP, which in turn heterodimerizes and suppresses FTF transactivation activity; and 2) it occupies the FTF/ HNF-4 recognition site within the 7␣-and 12␣-hydroxylase promoters, which can otherwise be occupied by a factor (HNF-4) that cannot be suppressed by SHP.

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Section: Methodsmentioning

confidence: 99%

The Role of α1-Fetoprotein Transcription Factor/LRH-1 in Bile Acid Biosynthesis

Castillo-Olivares

Campos

Pandak

et al. 2004

Journal of Biological Chemistry

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“…Enhanced rates of bile acid synthesis also occur in both rats and mice after overexpression of STARD1 in the liver, providing evidence for an in vivo function (Ren et al 2004a,b). A key finding of these studies is that the transport of cholesterol into the mitochondria is rate-limiting for bile acid synthesis by the CYP27A1 alternative pathway, suggesting that cholesterol transport into hepatic mitochondria may be regulated under normal or pathological conditions (Pandak et al 2002). Importantly, STARD1 expression in human HepG2 hepatoma cells is increased by treatment with 27HC or by induced expression of CYP27A1, the enzyme that metabolizes cholesterol to 27HC.…”

Section: Stard1 and Oxysterol Production In Non-steroidogenic Tissuesmentioning

confidence: 90%

“…One of the first reported roles for STARD1 outside of steroidogenic cells was in cholesterol transfer across the mitochondrial membranes in the liver for initiation of bile acid synthesis by the alternative pathway. Overexpression of STARD1 significantly increases 27HC and bile acid synthesis in primary rat or mouse hepatocytes or human HepG2 hepatoma cells (Pandak et al 2002, Ren et al 2004a,b, Hall et al 2005. Enhanced rates of bile acid synthesis also occur in both rats and mice after overexpression of STARD1 in the liver, providing evidence for an in vivo function (Ren et al 2004a,b).…”

Section: Stard1 and Oxysterol Production In Non-steroidogenic Tissuesmentioning

confidence: 99%

The mammalian START domain protein family in lipid transport in health and disease

Clark¹

2011

Journal of Endocrinology

135

109

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Lipid transfer proteins of the steroidogenic acute regulatory protein-related lipid transfer (START) domain family are defined by the presence of a conserved w210 amino acid sequence that folds into an a/b helix-grip structure forming a hydrophobic pocket for ligand binding. The mammalian START proteins bind diverse ligands, such as cholesterol, oxysterols, phospholipids, sphingolipids, and possibly fatty acids, and have putative roles in non-vesicular lipid transport, thioesterase enzymatic activity, and tumor suppression. However, the biological functions of many members of the START domain protein family are not well established. Recent research has focused on characterizing the cell-type distribution and regulation of the START proteins, examining the specificity and directionality of lipid transport, and identifying disease states associated with dysregulation of START protein expression. This review summarizes the current concepts of the proposed physiological and pathological roles for the mammalian START domain proteins in cholesterol and lipid trafficking.

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“…Twenty- (23) of the culture medium with chloroform/methanol (2:1, v/v). Where indicated, the cells were infected at a multiplicity of infection of 40 of an adenovirus encoding the steroidogenic acute regulatory domain 1 cDNA driven by the cytomegalovirus promoter (24) in 0.5 ml of serum-free medium. After 2 h, the virus was diluted, and […”

Section: Methodsmentioning

confidence: 99%

“…Bile acid levels inside the cells showed a decreasing trend, although it was statistically insignificant. As a positive control we used cells overexpressing steroidogenic acute regulatory domain protein 1, which we have shown to increase bile acid synthesis (24). Bile acids excreted in the medium of steroidogenic acute regulatory domain protein 1-infected cells increased 11-fold compared with control (data not shown).…”

Section: Decreased 7␣-hydroxylase Expression In Primary Rat Hepatocytmentioning

confidence: 99%

Activation of Bile Acid Biosynthesis by the p38 Mitogen-activated Protein Kinase (MAPK)

Tavares-Sanchez

et al. 2007

Journal of Biological Chemistry

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Bile acids are required for intestinal absorption and biliary solubilization of cholesterol and lipids. In addition, bile acids play a crucial role in cholesterol homeostasis. One of the key enzymes in the bile acid biosynthetic pathways is cholesterol 7␣-hydroxylase/cytochrome P450 7␣-hydroxylase (7␣-hydroxylase), which is the rate-limiting and regulatory step of the "classic" pathway. Transcription of the 7␣-hydroxylase gene is highly regulated. Two nuclear receptors, hepatocyte nuclear factor 4␣ (HNF-4␣) and ␣ 1 -fetoprotein transcription factor, are required for both transcription and regulation by different physiological events. It has been shown that some mitogen-activated protein kinases, such as the c-Jun N-terminal kinase and the ERK, play important roles in the regulation of 7␣-hydroxylase transcription. In this study, we show evidence that the p38 kinase pathway plays an important role in 7␣-hydroxylase expression and hence in bile acid synthesis. Inhibition of p38 kinase activity in primary hepatocytes results in ϳ5-10-fold reduction of 7␣-hydroxylase mRNA. This suppression is mediated, at least in part, through HNF-4␣. Inhibition of p38 kinase activity diminishes HNF-4␣ nuclear protein levels and its phosphorylation in vivo and in vitro, and it renders a less stable protein. Induction of the p38 kinase pathway by insulin results in an increase in HNF-4␣ protein and a concomitant induction of 7␣-hydroxylase expression that is blocked by inhibiting the p38 pathway. These studies show a functional link between the p38 signaling pathway, HNF-4␣, and bile acid synthesis.

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Transport of Cholesterol into Mitochondria Is Rate-limiting for Bile Acid Synthesis via the Alternative Pathway in Primary Rat Hepatocytes

Cited by 117 publications

References 28 publications

The Role of α1-Fetoprotein Transcription Factor/LRH-1 in Bile Acid Biosynthesis

The Role of α1-Fetoprotein Transcription Factor/LRH-1 in Bile Acid Biosynthesis

The mammalian START domain protein family in lipid transport in health and disease

Activation of Bile Acid Biosynthesis by the p38 Mitogen-activated Protein Kinase (MAPK)

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