Role of N-linked glycosylation in the secretion and activity of endothelial lipase

Miller, Gwen C.; Long, Christopher J.; Bojilova, Ekaterina; Marchadier, Dawn; Badellino, Karen O.; Blanchard, Nadine; Fuki, Ilia V.; Glick, Jane M.; Rader, Daniel J.

doi:10.1194/jlr.m400162-jlr200

Cited by 30 publications

(46 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…4A) and that some of these partially cleaved forms could potentially retain catalytic activity. The lack of enzymatic activity of the N-terminal portion of EL (14) indicates that an interaction with the C-terminal domain is essential to activity. Even if EL is active as a dimer in a head-to-tail conformation, other intermediate forms could potentially also be active as long as an intact active site is present and the contribution of the C-terminal domain is preserved.…”

Section: Table 1 Triglyceride Lipase and Phospholipase Activities Of mentioning

confidence: 99%

“…4 Thus, the presence of the C-terminal domain is necessary for activity. All three enzymes are glycosylated to varying degrees, and two of the glycosylation sites (one each in the N-and C-terminal domains) are common to all three enzymes (14,15). All three enzymes are also heparin-binding proteins, and regions that contribute to heparin binding are found in both the N-and C-terminal domains (16 -18).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Identification of the Active Form of Endothelial Lipase, a Homodimer in a Head-to-Tail Conformation

Griffon

Jin²,

Petty

et al. 2009

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Endothelial lipase (EL) is a member of a subfamily of lipases that act on triglycerides and phospholipids in plasma lipoproteins, which also includes lipoprotein lipase and hepatic lipase. EL has a tropism for high density lipoprotein, and its level of phospholipase activity is similar to its level of triglyceride lipase activity. Inhibition or loss-of-function of EL in mice results in an increase in high density lipoprotein cholesterol, making it a potential therapeutic target. Although hepatic lipase and lipoprotein lipase have been shown to function as homodimers, the active form of EL is not known. In these studies, the size and conformation of the active form of EL were determined. Immunoprecipitation experiments suggested oligomerization. Ultracentrifugation experiments showed that the active form of EL had a molecular weight higher than the molecular weight of a simple monomer but less than a dimer. A construct encoding a covalent head-to-tail homodimer of EL (EL-EL) was expressed and had similar lipolytic activity to EL. The functional molecular weights determined by radiation inactivation were similar for EL and the covalent homodimer EL-EL. We previously showed that EL could be cleaved by proprotein convertases, such as PC5, resulting in loss of activity. In cells overexpressing PC5, the covalent homodimeric EL-EL appeared to be more stable, with reduced cleavage and conserved lipolytic activity. A comparative model obtained using other lipase structures suggests a structure for the head-to-tail EL homodimer that is consistent with the experimental findings. These data confirm the hypothesis that EL is active as a homodimer in head-to-tail conformation.Three members of the triglyceride lipase family, lipoprotein lipase (LPL), 3 hepatic lipase (HL), and endothelial lipase (EL), contribute to lipoprotein catabolism in the plasma compartment. They are all secreted proteins that bind to heparan sulfate proteoglycans on the luminal side of endothelial cells where they interact with their lipoprotein substrates. They have different specificities for lipoproteins, and all hydrolyze triglycerides and phosphatidylcholine at the sn-1 position, albeit with widely differing efficiencies (1). The preferred lipoprotein substrates for LPL are the triglyceride-rich lipoproteins, chylomicrons, and very low density lipoproteins; the triglyceride lipase activity of LPL is more than 100-fold greater than its phospholipase activity. The primary lipoprotein substrates for HL are chylomicron remnants, intermediate density lipoproteins, and large triglyceridase-enriched HDL; its triglyceride lipase activity is about 20-fold higher than its phospholipase activity. EL is much more active on HDL, and its phospholipase activity is quite similar to its triglyceride lipase activity. These three lipolytic enzymes share a number of structural features. By analogy to the crystal structure of pancreatic lipase (2), another member of the triglyceride lipase family, each has a clearly defined N-terminal and C-terminal structural domain, ...

show abstract

Section: Table 1 Triglyceride Lipase and Phospholipase Activities Of mentioning

confidence: 99%

mentioning

confidence: 99%

Identification of the Active Form of Endothelial Lipase, a Homodimer in a Head-to-Tail Conformation

Griffon

Jin²,

Petty

et al. 2009

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

show abstract

“…Miller et al reported that Asn-60 mutation markedly reduced its secretion, Asn-116 mutation increased phospholipase activity, and Asn-373 mutation reduced EL activity and its lipid-binding function. 9 Brown et al reported that the specific hydrolytic activity toward LDL by EL-N116A was significantly greater than wild-type EL in vitro. 40 In addition, adenovirus encoding wild-type EL reduced plasma HDL-C levels dominantly, whereas that encoding Asn-116 mutant EL reduced both HDL-C and LDL-C in LDLR −/− mice.…”

Section: El In Hdl Metabolism Rct and Atherosclerosismentioning

confidence: 99%

“…Mature EL is a 68-kD glycoprotein, 9 and it shares amino acid sequence similarity with lipases, having 44% amino acid identity to LPL and 41% amino acid identity to HL. 10 However, the sequence homology of the lid lesion, which determines the specificity of lipases, largely differs between EL and LPL or HL (Table).…”

Section: El Belongs To the Lpl Familymentioning

confidence: 99%

Update on the Role of Endothelial Lipase in High-Density Lipoprotein Metabolism, Reverse Cholesterol Transport, and Atherosclerosis

Yasuda

Ishida

Rader

2010

Circ J

Self Cite

107

108

View full text Add to dashboard Cite

Endothelial lipase (EL) is a phospholipase that belongs to the lipoprotein lipase (LPL) family, which includes LPL and hepatic lipase (HL). Similar to LPL and HL, EL regulates lipoprotein metabolism, mainly high-density lipoprotein (HDL) metabolism and HDL cholesterol (HDL-C) levels in humans and mice. Existing data strongly suggest that inhibition of EL in humans would be expected to increase the HDL-C level. However, it has not been definitively established whether the effect of EL activity on HDL-C levels translates into effects on reverse cholesterol transport or atherosclerosis. The available data regarding the impact of EL expression and activity on HDL metabolism, reverse cholesterol transport, and atherosclerosis are reviewed. (Circ J 2010; 74: 2263 - 2270

show abstract

“…In particular, N-linked glycosylation at positions 43, 56 and 62 of LPL, HL and EL ( Figure 2A, arrows) is critical for efficient maturation. Studies have demonstrated that removal of these conserved sites by site-directed mutagenesis results in severe maturation defects, as evidenced by ER retention of lipase proteins and, at least for LPL and HL, the abolishment of enzyme activity [77][78][79]. These critical glycosylation sites are adjacent to a pair of cysteine residues forming the first disulfide bridge, and near the lid domain that shields hydrophobic residues within the active site cleft [8,18].…”

Section: Lipase Glycosylation and Processing In The Endoplasmic Reticulummentioning

confidence: 99%

Mechanisms of lipase maturation

Doolittle

Péterfy

2010

Clinical Lipidology

View full text Add to dashboard Cite

Lipases are acyl hydrolases that represent a diverse group of enzymes present in organisms ranging from prokaryotes to humans. This article focuses on an evolutionarily related family of extracellular lipases that include lipoprotein lipase, hepatic lipase and endothelial lipase. As newly synthesized proteins, these lipases undergo a series of co-and post-translational maturation steps occurring in the endoplasmic reticulum, including glycosylation and glycan processing, and protein folding and subunit assembly. This article identifies and discusses mechanisms that direct early and late events in lipase folding and assembly. Lipase maturation employs the two general chaperone systems operating in the endoplasmic reticulum, as well as a recently identified lipase-specific chaperone termed lipase maturation factor 1. We propose that the two general chaperone systems act in a coordinated manner early in lipase maturation in order to help create partially folded monomers; lipase maturation factor 1 then facilitates final monomer folding and subunit assembly into fully functional homodimers. Once maturation is complete, the lipases exit the endoplasmic reticulum and are secreted to extracellular sites, where they carry out a number of functions related to lipoprotein and lipid metabolism.

show abstract

Role of N-linked glycosylation in the secretion and activity of endothelial lipase

Cited by 30 publications

References 33 publications

Identification of the Active Form of Endothelial Lipase, a Homodimer in a Head-to-Tail Conformation

Identification of the Active Form of Endothelial Lipase, a Homodimer in a Head-to-Tail Conformation

Update on the Role of Endothelial Lipase in High-Density Lipoprotein Metabolism, Reverse Cholesterol Transport, and Atherosclerosis

Mechanisms of lipase maturation

Contact Info

Product

Resources

About