Regulation of lipoprotein lipase translation by epinephrine in 3T3-L1 cells. Importance of the 3' untranslated region.

Yukht, Ada; Davis, Richard C.; Ong, John M.; Ranganathan, Gouri; Kern, Philip A.

doi:10.1172/jci118301

Cited by 32 publications

(46 citation statements)

References 46 publications

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“…In addition to the presence of potential transcriptional regulatory elements in the 3' region, translational regulatory elements in the 3' region of the LPL gene have also been identified [42][43][44]. A recent study suggests that regulatory polymorphisms are complex and sensitive to modifiers with multiple trans-acting or environmental factors affecting their function [45].…”

Section: Discussionmentioning

confidence: 99%

Functional significance of lipoprotein lipase HindIII polymorphism associated with the risk of coronary artery disease

et al. 2008

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Lipoprotein Lipase (LPL) plays a pivotal role in lipid metabolism by hydrolyzing triglyceride (TG) rich lipoprotein particles. Abnormalities in normal LPL function are associated with the risk of coronary artery disease (CAD). A number of genetic variants have been identified in the LPL gene that affects different functions of the LPL protein. A common HindIII polymorphism in intron 8 (T/ G) of the LPL gene has been found to be associated with altered plasma TG and HDL-cholesterol, and CAD risk in several studies, but its functional significance is unknown. It has been shown that certain intronic sequence contain regulatory elements that are important for transcription and translational regulation of a gene. In this study we tested the hypothesis that this polymorphism affects the binding site of a transcription factor that regulates the transcription of LPL gene. Electrophoretic mobility shift assays revealed that the HindIII site binds to a transcription factor and that the mutant allele has lower binding affinity than the wild type allele. Transcription assays containing the entire intron 8 sequence along with full-length human LPL promoter were carried out in COS-1 and human vascular smooth muscle cells. The mutant allele was associated with significantly decreased luciferase expression level compared to the wild type allele in both the muscle (3.394 ± 0.022 vs. 4.184 ± 0.028; P=4.7 × 10 −6 ) and COS-1 (11.603 ± 0.409 vs. 14.373 ± 1.096; P<0.0001) cells. In conclusion, this study demonstrates for the first time that the polymorphic HindIII site in the LPL gene is functional because it affects the binding of a transcription factor and it also has an impact on LPL expression.

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Section: Discussionmentioning

confidence: 99%

Functional significance of lipoprotein lipase HindIII polymorphism associated with the risk of coronary artery disease

et al. 2008

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“…Polysome Preparation and Reverse Transcription-PCR-The polysome profiles were obtained as described previously (3,6,26). In brief, postmitochondrial supernatants were prepared from control and TPAtreated 3T3-F442A adipocytes and reconstituted with 0.25 M sucrose and layered over a 10 -50% sucrose gradient.…”

Section: Methodsmentioning

confidence: 99%

“…The regulation of LPL is complex and may occur at the level of transcription, translation, or post-translational processing. We have previously described translational regulation of LPL in adipocytes in response to thyroid hormone and catacholamines (3,4). This translational regulation is likely due to the presence of an RNA-binding protein that interacts with the 3Ј-UTR of the LPL mRNA (5).…”

Section: Lipoprotein Lipase (Lpl)mentioning

confidence: 99%

Regulation of Lipoprotein Lipase by Protein Kinase Cα in 3T3-F442A Adipocytes

Ranganathan¹,

Song²,

Dean³

et al. 2002

Journal of Biological Chemistry

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Lipoprotein lipase (LPL) is an important enzyme in adipocyte and lipid metabolism with complex cellular regulation. Previous studies demonstrated an inhibition of LPL activity and synthesis following depletion of protein kinase C (PKC) isoforms with long term treatment of 3T3-F442A adipocytes with 12-O-tetradecanoylphorbol-13-acetate. To identify the specific PKC isoforms involved, we treated cells with antisense oligonucleotides that block expression of specific PKC isoforms. An antisense oligonucleotide to PKC␣ inhibited LPL activity by 78 ؎ 8%, whereas antisense oligonucleotides directed against PKC␦ or PKC⑀ had no effect on LPL activity. The change in LPL activity was maximal at 72 h and was accompanied by a decrease in LPL protein and LPL synthetic rate but no change in LPL mRNA, suggesting regulation at the level of translation. However, PKC depletion resulted in no change in the polysome profile, indicating that translation initiation was not affected. However, the addition of cytoplasmic extracts from adipocytes treated with 12-O-tetradecanoylphorbol-13-acetate or PKC␣ antisense oligomers inhibited LPL translation in vitro. This inhibition of LPL translation in vitro was lost when the LPL mRNA transcript did not contain nucleotides 1599 -3200, thus implicating the 3-untranslated region of LPL in the regulation of translation by PKC depletion. Both LPL activity and Raf1 activity were decreased in parallel following depletion of either total PKC or specific inhibition of PKC␣. An antisense oligonucleotide to RAF1, which inhibited RAF1 activity, also inhibited LPL activity by 48 ؎ 10%, and this decrease in LPL activity was not accompanied by a change in LPL mRNA. Cells were treated with U0126, a specific inhibitor of the ERK-activating kinases MEK1 and MEK2. Although U0126 inhibited ERK1 and ERK2 phosphorylation, U0126 had no effect on LPL activity, indicating that MEK/ERK pathways were not involved in this mechanism of LPL regulation. Together, these data indicate that PKC␣ and RAF1 are important in the translational regulation of LPL in adipocytes and that the mechanism of regulation is probably through an ERK-independent pathway.

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“…This up-regulation of hLPLe translation is likely due to the absence of the 3Ј-UTR of the hLPLe construct. As described in previous studies, LPL translation is inhibited by epinephrine and thyroid hormone due to the stimulation of an RNAbinding protein that interacts with the first 24 -40 nucleotides of the 3Ј-UTR (39,40). Both epinephrine and thyroid hormone are constitutively present, and hypothyroid rats demonstrate a translational up-regulation of LPL (41).…”

Section: Fig 10mentioning

confidence: 75%

“…In in vitro studies, this regulation is dependent on the presence of the first 24 nucleotides of the 3Ј-UTR of LPL (39) and occurs at the level of translation. Thus, mice expressing LPL in adipose tissue with the hLPLe construct described herein would be predicted to have up-regulated LPL translation.…”

Section: Fig 10mentioning

confidence: 99%

Transgenic Mice Expressing Lipoprotein Lipase in Adipose Tissue

Hensley

Ranganathan

Wagner

et al. 2003

Journal of Biological Chemistry

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Lipoprotein lipase (LPL) is a key enzyme in lipoprotein and adipocyte metabolism. Defects in LPL can lead to hypertriglyceridemia and the subsequent development of atherosclerosis. The mechanisms of regulation of this enzyme are complex and may occur at multiple levels of gene expression. Because the 3 -untranslated region (UTR) is involved in LPL translational regulation, transgenic mice were generated with adipose tissue expression of an LPL construct either with or without the proximal 3 -UTR and driven by the aP2 promoter. Both transgenic mouse colonies were viable and expressed the transgene, resulting in a 2-fold increase in LPL activity in white adipose tissue. Neither mouse colony exhibited any obvious phenotype in terms of body weight, plasma lipids, glucose, and non-esterified fatty acid levels. In the mice expressing hLPL with an intact 3 -UTR, hLPL mRNA expression approximately paralleled hLPL activity. However in the mice without the proximal 3 -UTR, hLPL mRNA was low in the setting of large amounts of hLPL protein and LPL activity. In previous studies, the 3 -UTR of LPL was critical for the inhibitory effects of constitutively expressed hormones, such as thyroid hormone and catecholamines. Therefore, these data suggest that the absence of the 3 -UTR results in a translationally unrepressed LPL, resulting in a moderate overexpression of adipose LPL activity.Lipoprotein lipase (LPL) 1 is a central enzyme in lipid metabolism. The enzyme is synthesized and secreted by adipocytes and muscle cells, and transported to the capillary endothelium, where hydrolysis of the triglyceride core of circulating VLDL and chylomicrons takes place. Although the changes in LPL activity with different physiologic states have been well described (1), the mechanism of LPL regulation is complex and occurs at levels of transcription (2-6), translation (7-11), and post-translational processing (12-15) in response to both cell type and regulatory factors. Previous studies have demonstrated translational regulation of LPL. In response to glucose (7), thyroid hormone (8), and catecholamines (9), there were significant changes in LPL protein synthesis, with no changes in adipocyte LPL mRNA levels. In addition, the decrease in LPL activity in both diabetic patients, and rats is due predominantly to decreased LPL translation (10, 16).LPL is an important marker of adipocyte differentiation, and LPL expression increases in parallel with cellular triglyceride accumulation in preadipocytes (17, 18). Although adipose tissue can synthesize non-esterified fatty acids (NEFA) de novo, NEFA for lipid storage are preferentially obtained from LPLmediated hydrolysis of plasma lipoproteins (19). Hence, LPL has been called "the gatekeeper of the adipocyte" (20), and has been implicated in the development of obesity.Based on LPL's putative role as an adipocyte "gatekeeper," one might expect that transgenic mice would become obese if LPL were overexpressed in adipose tissue, and lean if LPL were overexpressed in muscle. Several recent studies have ...

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Regulation of lipoprotein lipase translation by epinephrine in 3T3-L1 cells. Importance of the 3' untranslated region.

Cited by 32 publications

References 46 publications

Functional significance of lipoprotein lipase HindIII polymorphism associated with the risk of coronary artery disease

Functional significance of lipoprotein lipase HindIII polymorphism associated with the risk of coronary artery disease

Regulation of Lipoprotein Lipase by Protein Kinase Cα in 3T3-F442A Adipocytes

Transgenic Mice Expressing Lipoprotein Lipase in Adipose Tissue

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