Expression in Xenopus oocytes of rat liver mRNA coding for a bile salt-dependent cholesteryl ester hydrolase.

Zolfaghari, Reza; Harrison, Earl H.; Ross, Alastair; Fisher, Edward A.

doi:10.1073/pnas.86.18.6913

Cited by 20 publications

(13 citation statements)

References 19 publications

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“…The identity of a second cytosolic cholesterol esterase as being CEL was first established by Camulli et al (6), who purified the protein from rat liver and showed that it was identical to the pancreatic enzyme based on immunoreactivity with CEL-specific antibodies, bile salt activation, and N-terminal amino acid sequencing. These results were subsequently confirmed by RNA analysis (4,7,65). The hepatic CEL was found to be present in specific endosomal compartments of hepatocytes (127).…”

Section: Hepatic Lipoprotein Metabolismsupporting

confidence: 67%

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Carboxyl ester lipase

Hui

Howles

2002

Journal of Lipid Research

196

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Carboxyl ester lipase (CEL), previously named cholesterol esterase or bile salt-stimulated (or dependent) lipase, is a lipolytic enzyme capable of hydrolyzing cholesteryl esters, tri-, di-, and mono-acylglycerols, phospholipids, lysophospholipids, and ceramide. The active site catalytic triad of serine-histidine-aspartate is centrally located within the enzyme structure and is partially covered by a surface loop. The carboxyl terminus of the protein regulates enzymatic activity by forming hydrogen bonds with the surface loop to partially shield the active site. Bile salt binding to the loop domain frees the active site for accessibility by water-insoluble substrates. CEL is synthesized primarily in the pancreas and lactating mammary gland, but the enzyme is also expressed in liver, macrophages, and in the vessel wall. In the gastrointestinal tract, CEL serves as a compensatory protein to other lipolytic enzymes for complete digestion and absorption of lipid nutrients. Importantly, CEL also participates in chylomicron assembly and secretion, in a mechanism mediated through its ceramide hydrolytic activity. Cell culture studies suggest a role for CEL in lipoprotein metabolism and oxidized LDL-induced atherosclerosis. Thus, this enzyme, which has a wide substrate reactivity and diffuse anatomic distribution, may have multiple functions in lipid and lipoprotein metabolism, and atherosclerosis. Carboxyl ester lipase (CEL), previously named pancreatic cholesterol esterase and also known as bile salt-stimulated (or -dependent) lipase, is a nonspecific lipolytic enzyme capable of hydrolyzing cholesteryl esters, tri-, di-, and mono-acylglycerols, phospholipids, lysophospholipids, and ceramide (1-3). The hydrolysis of water-insoluble carboxyl esters with long chain fatty acyl groups by CEL requires its activation by bile salt. However, CEL hydrolysis of water-soluble substrates such as carboxyl esters with short chain fatty acids or lysophospholipids does not have an absolute dependence on bile salt activation. The CEL protein is synthesized primarily in the pancreatic acinar cells and lactating mammary glands of higher mammals. Small amounts of CEL are found in other tissues, particularly the liver, macrophages, endothelial cells, and eosinophils (4-10). Extensive research has been performed in recent years on the structure-function relationship of this protein as well as its physiological role in lipid metabolism. A significant body of work has also been devoted to studying CEL processing and transport in pancreatic acinar cells. The latter topic was reviewed recently (11) and will be discussed only briefly in this article when appropriate. This article will present an updated review on the structure-function studies of CEL as well as an in-depth discussion on the current understanding of its role in lipid metabolism. PROTEIN STRUCTURE-FUNCTION RELATIONSHIP Active siteThe nucleotide sequence of CEL from various species shows that it is a highly conserved protein belonging to the ␣ / ␤ hydrolase family. The carb...

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Section: Hepatic Lipoprotein Metabolismsupporting

confidence: 67%

“…In addition to its presence in the digestive tract, CEL is synthesized in liver (4,7,65), macrophages (9,46), endothelial cells (10), and heart (116). CEL protein and enzyme activity are also found in the circulation (117)(118)(119).…”

Section: Lipoprotein Metabolism and Atherosclerosismentioning

confidence: 99%

Carboxyl ester lipase

Hui

Howles

2002

Journal of Lipid Research

196

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“…8 -11 In subsequent studies, however, we showed that RNA extracted from a pool of rat livers contained CEH mRNA, indicating at least in some cases, a capacity for hepatic synthesis of the enzyme. 12 These findings were confirmed and extended by Hui, Brockman, and their colleagues (Kissel et al 2 and Camulli et al 13 ), who reported that the rat liver can contain both mRNA and protein species indistinguishable from pCEH message and protein. However, Schotz and his colleagues (Reue et al u ) have recently reported that rat liver does not contain CEH mRNA.…”

supporting

confidence: 76%

“…12 Briefly, for each RNA sample, 25-50 oocytes collected from Xenopus laevis were injected with 50 nl of a solution of either mRNA (2 mg/ml in water) or total RNA (3 mg/ml). Oocytes were incubated at 19°C for 3-5 days.…”

Section: Preparation and Microinjection Of Xenopus Laevis Oocytesmentioning

confidence: 99%

Tissue and species differences in bile salt-dependent neutral cholesteryl ester hydrolase activity and gene expression.

Zolfaghari

Harrison

Han

et al. 1992

Arterioscler Thromb

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Enzymatic activity and raRNA abundance for neutral bile salt-dependent cholesteryl ester hydrolase (CEH) were determined in rat and rabbit tissues. In rat liver and intestine, enzyme activity and mRNA levels varied independently. Particularly striking in most tissue samples was the absence of detectable CEH mRNA in the presence of enzymatic activity, suggesting that there was an exogenous source of enzyme. Rabbits differed from rats in four ways. First, neither CEH activity nor mRNA was present in any liver sample. Second, CEH mRNA was present in nearly all intestinal samples, and its abundance tended to correlate with enzymatic activity. Third, rabbit CEH mRNA was approximately 250 bases shorter than the rat message. Fourth, we have previously shown that rat plasma contains CEH activity, whereas in the present studies, rabbit plasma did not contain such activity. Overall, our studies indicate that CEH activity in rat liver, intestine, and plasma can be derived exogenously, most likely from the uptake and transport of pancreatic enzyme. In contrast, in rabbit the lack of CEH activity in plasma and liver and the capacity of the intestine for in situ synthesis of CEH suggest that this animal does not have the same ability to distribute pancreatic CEH. These species differences in CEH metabolism may partly explain the greater susceptibility of rabbit tissues to accumulate cholesteryl esters. The regulation of this process is not well defined. For example, only one enzyme present in these organs and having significant hydrolytic activity against cholesteryl esters at neutral pH, bile salt-dependent cholesteryl ester hydrolase (CEH), has been characterized at the molecular level. 1 -3 In previous studies, we have reported that CEH activity in the rat liver and intestine is quite variable among individual animals. Moreover, the properties of the enzymatic activity in both tissues were remarkably similar to purified pancreatic CEH (pCEH) and were, in fact, specifically and completely inhibited by an antibody to pCEH. 4 It has been known for some time that pCEH is secreted into the intestinal lumen, where it participates in the processing of dietary lipid. In addition, there is evidence that pCEH is internalized by the intestinal mucosal cells and participates in the intracellular metabolism of cholesteryl esters (for example, see

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“…Total RNA was isolated from hepatic cells at the conclusion of the experiments using a guanidinium thiocyanate-based procedure ( 19) as previously described (20). RNA samples were blotted onto nylon membranes (Nytran, Schleicher & Schuell, Inc., Keene, NH), using a Bio-Rad Laboratories (Richmond, CA) manifold following the manufacturer's protocol.…”

Section: Rna Isolation and Quantitationmentioning

confidence: 99%

N-3 fatty acids stimulate intracellular degradation of apoprotein B in rat hepatocytes.

Wang¹,

Chen²,

Fisher³

1993

J. Clin. Invest.

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131

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When rat hepatocytes were incubated with albumin complexed to the n-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), rather than to oleic acid (OA), the secretion of newly synthesized apoprotein B100 (apoB100) or B48 (apoB48) was reduced, despite stimulation of cellular triglyceride synthesis by all three fatty acids. When pulse-chase studies of apoB synthesis and secretion were performed in the presence of OA, EPA, or DHA, there were no significant changes in the initial synthetic rates of either apoB species. However, during the chase period, the total recovery of labeled apoB100 and apoB48 from the cell and medium was less in the n-3 fatty acid groups, so that by 150 min, approximately half as much labeled apoB was recovered as in the OA group. Overall, the decreased accumulation in medium of labeled apoB in the presence of EPA and DHA could be quantitatively accounted for by increased degradation of intracellular apoB. Thus, in the primary hepatocyte, apoB degradation is not constitutive, but can be regulated by n-3 fatty acids. (J. Clin. Invest. 1993.

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Expression in Xenopus oocytes of rat liver mRNA coding for a bile salt-dependent cholesteryl ester hydrolase.

Abstract: BiochemistryExpression in Xenopus oocytes of rat liver mRNA coding for a bile salt-dependent cholesteryl ester hydrolase (pancreatic cholesteryl esterase/neutral cholesteryl esterase/sodium cholate)

Cited by 20 publications

References 19 publications

Carboxyl ester lipase

Carboxyl ester lipase

Tissue and species differences in bile salt-dependent neutral cholesteryl ester hydrolase activity and gene expression.

N-3 fatty acids stimulate intracellular degradation of apoprotein B in rat hepatocytes.

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