Maturation of Lipoprotein Lipase in the Endoplasmic Reticulum

Ben-Zeev, Osnat; Mao, Hui Z.; Doolittle, Mark H.

doi:10.1074/jbc.m108128200

Cited by 60 publications

(45 citation statements)

References 77 publications

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“…The half-time for LPL activity was about 12 h, which did not indicate rapid unfolding/degradation, and no LPL aggregates were found in the media by sucrose density centrifugation. The LPL protein seemed to be properly coreglycosylated, which in other systems has been shown to be a prerequisite for activity (12)(13)(14)(15)(16)(17)(18). Furthermore, secretion of the LPL protein was probably not limiting, because the ratio between active and inactive LPL was similar inside and outside the cells.…”

Section: Table II Effect Of Co-expression With Crt On Lpl Dimermentioning

confidence: 97%

“…There were at least two possible explanations for these results. One was that the low synthesis was only apparent and due to rapid degradation of misfolded/ aggregated LPL protein (18). Another was that the activation and/or the secretion processes were impaired.…”

Section: Table II Effect Of Co-expression With Crt On Lpl Dimermentioning

confidence: 99%

“…Therefore, chromatography on heparin-Sepharose is widely used to separate inactive forms of LPL from active dimers (18,37). The extended molecular shape of the LPL subunits precludes separation of monomers and dimers by gel permeation chromatography (7).…”

Section: Glycosylated Human Lpl Was Expressed In the Baculovirusmentioning

confidence: 99%

“…This suggests that N-linked carbohydrate chains play important roles in the initial folding of LPL. Doolittle and co-workers (25) demonstrated that the chaperone CNX is downregulated in mice with functional LPL and HL deficiency due to the cld/cld mutation and more recently (18) that ER chaperones may be involved in prevention of aggregation of newly synthesized LPL. In accordance, Boedeker et al (26) found that CNX increased the efficiency of export of active human HL from the ER of transfected Chinese hamster ovary cells and also demonstrated interaction of HL with the chaperone.…”

mentioning

confidence: 99%

“…Studies using site-directed mutagenesis and inhibitors of transport between ER and Golgi have shown that core glycosylation at residue Asn 43 is necessary for activation and release of LPL from the ER, but glycosylation at Asn 359 is not necessary (9 -11). A number of studies have suggested that proper folding, dimerization, and activation of LPL occurs already in the ER (12)(13)(14)(15)(16)(17)(18), but no specific factors involved in the acquisition of the active conformation have yet been identified.…”

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confidence: 99%

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Calreticulin Promotes Folding/Dimerization of Human Lipoprotein Lipase Expressed in Insect Cells (Sf21)

Zhang

Tate

et al. 2003

Journal of Biological Chemistry

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Lipoprotein lipase (LPL) is a non-covalent, homodimeric, N-glycosylated enzyme important for metabolism of blood lipids. LPL is regulated by yet unknown post-translational events affecting the levels of active dimers. On co-expression of LPL with human molecular chaperones, we found that calreticulin had the most pronounced effects on LPL activity, but calnexin was also effective. Calreticulin caused a 9-fold increase in active LPL, amounting to about 50% of the expressed LPL protein. The total expression of LPL protein was increased less than 20%, and the secretion rates for active and inactive LPL were not significantly changed by the chaperone. Thus, the main effect was an increased specific activity of LPL both in cells and media. Chromatography on heparin-Sepharose and sucrose density gradient centrifugation demonstrated that most of the inactive LPL was monomeric and that calreticulin promoted formation of active dimers. Higher oligomers of inactive LPL were present in cell extracts, but only monomers and dimers were secreted to the medium. Interaction between LPL and calreticulin was demonstrated, and the effect of the chaperone was prevented by castanospermine, an inhibitor of N-glycan glucose trimming. Our data indicate an important role of endoplasmic reticulum-based chaperones for the folding/ dimerization of LPL. Lipoprotein lipase (LPL)1 hydrolyzes triglycerides in the circulating plasma lipoproteins, such as chylomicrons and very low density lipoproteins (1-3). The enzyme is produced and secreted mainly by adipocytes and muscle cells, but it is also produced in other cells such as macrophages and certain neurons. LPL is transported by yet unclear mechanisms to the vascular endothelium, where it is attached to cell surfaces through interaction with heparan sulfate proteoglycans (HSPG). The products of lipolysis are taken up for storage or oxidation in adjacent tissues. In addition, LPL can mediate internalization of intact lipoproteins by bridging them to cell surface receptors like the LDL receptor-like protein or HSPG.LPL, along with pancreatic lipase, hepatic lipase (HL), and endothelial lipase, belongs to the gene family of mammalian triglyceride lipases (2, 4). The three-dimensional structure of LPL has not yet been determined. Based on homology with pancreatic lipase, it has been proposed that LPL has two structurally distinct regions, a larger N-terminal domain containing the active site and a smaller C-terminal domain with other important functions, such as binding to lipids, LDL receptorlike protein, and HSPG (5, 6).Catalytically active LPL is a non-covalent, homodimeric glycoprotein (7, 8). In the rough endoplasmic reticulum (ER), human LPL is co-translationally glycosylated at amino acid residues Asn 43 and Asn 359 . Studies using site-directed mutagenesis and inhibitors of transport between ER and Golgi have shown that core glycosylation at residue Asn 43 is necessary for activation and release of LPL from the ER, but glycosylation at Asn 359 is not necessary (9 -11). A number of studies...

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Section: Table II Effect Of Co-expression With Crt On Lpl Dimermentioning

confidence: 97%

Section: Table II Effect Of Co-expression With Crt On Lpl Dimermentioning

confidence: 99%

Section: Glycosylated Human Lpl Was Expressed In the Baculovirusmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Calreticulin Promotes Folding/Dimerization of Human Lipoprotein Lipase Expressed in Insect Cells (Sf21)

Zhang

Tate

et al. 2003

Journal of Biological Chemistry

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Effect of pu‐erh tea on body fat and lipid profiles in rats with diet‐induced obesity

Cao

Lin

et al. 2011

Phytotherapy Research

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The antiobesity and antihyperlipidaemic effects of pu-erh tea in rats with high fat diet (HFD)-induced obesity were investigated. Male Sprague-Dawley rats were randomly divided into five groups and fed varying diets for an 8-week period: control diet, HFD, and HFD supplemented with low, moderate or high doses of pu-erh tea extract (0.5 g, 2 g and 4 g/kg BW/day, respectively). Pu-erh tea significantly reduced the total body weight and the weight of various adipose pads. Pu-erh tea administration also significantly lowered plasma total cholesterol, triglyceride concentrations and low-density lipoprotein-cholesterol levels in rats with HFD-induced obesity, but did not affect high-density lipoprotein-cholesterol levels. Moreover, pu-erh tea significantly increased lipoprotein lipase, hepatic lipase and hormone-sensitive lipase activities in epididymal fat tissue in rats with HFD-induced obesity. Analysis of real-time reverse transcription-polymerase chain reaction results indicated that pu-erh tea significantly enhanced mRNA levels of hormone-sensitive lipase in rats with HFD-induced obesity. These results suggest that pu-erh tea attenuated visceral fat accumulation and improved hyperlipidemia in a rat model of HFD-induced obesity.

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The Ins and Outs of Adipose Tissue

Olivecrona

2009

Cellular Lipid Metabolism

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Maturation of Lipoprotein Lipase in the Endoplasmic Reticulum

Cited by 60 publications

References 77 publications

Calreticulin Promotes Folding/Dimerization of Human Lipoprotein Lipase Expressed in Insect Cells (Sf21)

Calreticulin Promotes Folding/Dimerization of Human Lipoprotein Lipase Expressed in Insect Cells (Sf21)

Effect of pu‐erh tea on body fat and lipid profiles in rats with diet‐induced obesity

The Ins and Outs of Adipose Tissue

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