Synthesis and Secretion of Hepatic Lipase by Rat Hepatocytes

Laposata, Elizabeth A.; StraussIII, Jerome F.; Laboda, Henry M.; Glick, Jane M.

doi:10.1007/978-1-4684-5296-9_6

Cited by 8 publications

(13 citation statements)

References 11 publications

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“…Antibody against human EL was generated to a peptide in the N-terminal region of EL, as previously described (33). Antibody to rat HL that cross-reacts with human HL was also previously described (46 I-labeled lipoproteins (5 g of protein/ml) unless otherwise stated. To assess the effects of endogenous expression of lipases on surface binding of lipoproteins, cells were incubated with labeled lipoproteins for 1 h at 4°C.…”

Section: Methodsmentioning

confidence: 99%

Endogenously Produced Endothelial Lipase Enhances Binding and Cellular Processing of Plasma Lipoproteins via Heparan Sulfate Proteoglycan-mediated Pathway

Fuki

Blanchard

Jin

et al. 2003

Journal of Biological Chemistry

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110

124

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Processing of LDL and HDL differed notably after initial binding via EL to the cell surface. More than 90% of the surface-bound125 I-LDL was destined for internalization and degradation, whereas about 70% of the surfacebound 125 I-HDL 3 was released back into the medium. These differences were significantly attenuated after HDL clustering was promoted using antibody against apolipoprotein A-I. At equal protein concentration of added lipoproteins the ratio of HDL 3 to VLDL bridging via EL was 0.092 compared with 0.174 via HL and 0.002 via LpL. In summary, EL mediates binding and uptake of plasma lipoproteins via a process that is independent of its enzymatic activity, requires cellular heparan sulfate proteoglycans, and is regulated by ligand clustering.

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Section: Methodsmentioning

confidence: 99%

Endogenously Produced Endothelial Lipase Enhances Binding and Cellular Processing of Plasma Lipoproteins via Heparan Sulfate Proteoglycan-mediated Pathway

Fuki

Blanchard

Jin

et al. 2003

Journal of Biological Chemistry

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110

124

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“…Rat liver ML in its mature form is a 59 kDa glycoprotein synthesised in hepatocytes and secreted into the blood stream [27,28]. Here it binds to the endothelial plasma membranes of liver, adrenals and ovaries [28][29][30], where it obviously plays an important role in lipoprotein metabolism [31,32].…”

Section: Resultsmentioning

confidence: 99%

Annexin II inhibits calcium‐dependent phospholipase A₁ and lysophospholipase but not triacyl glycerol lipase activities of rat liver hepatic lipase

et al. 1992

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A member of the unnexin family (the heterotctrameric annexin I12pl I2 camptcx purilied from porcine intestinal epithclium) was tcstcd for its ability to affect different calcium-dependent intrinsic lipolytic activities of rat liver hcpatic lipasc (HL). Whereas anncxin II in dc prcscnce of calcium failed to interfere with HL triacyl glycerol lipase (EC 3. I. I .3) activity, it inhibited HL phospholipasc A, (EC 3. I .1.32) and lysophospholipasc (EC 3.1.1.5) activities. Inhibition could be overcome by increasing the substrate concentration. Under phospholipasc A, assay conditions, anncxin II did not bind to the purilicd I-IL enzyme. These results thcrcforc suggest that only inhibitor/substrate interactions lead to inhibition of HL phospholipase A, and lysophospholipasc activities, an obviously general mechanism ofphospholipasc inhibition by annexins. Possible implications of HL inhibition in vivo by annexins are discussed.

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“…The latter enzyme, on the other hand, has three pairs of Cys residues (at positions 4, 10,90,101,103 and 181 in the porcine enzyme) not present in the hepatic or lipoprotein lipases. Furthermore, there are two glycosylation sites [9] known to be used [39] in rat hepatic lipase. They are present also in lipoprotein lipase and most probably used since this enzyme contains about 8% carbohydrate with a composition suggesting the presence of one high-mannose chain and at least one complex oligosaccharide chain [40].…”

Section: Discussionmentioning

confidence: 99%

Structural features of lipoprotein lipase

Persson¹,

Bengtsson‐Olivecrona²,

Enerbäck³

et al. 1989

European Journal of Biochemistry

135

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A structural homology between lipoprotein lipase, pancreatic lipase and hepatic lipase is known and indicates that all three lipases are members of a common protein family. Lipoprotein lipase and pancreatic lipase utilize small protein co-factors, apolipoprotein C-I1 and co-lipase, respectively, but comparisons reveal no homology between the co-factor molecules. Hence, they do not show the same relationship as their target enzymes. Neither do screenings detect any extensive similarities between lipoprotein lipase, serine hydrolases, or apolipoproteins. Scannings against data bank proteins show that a 105-residue segment of lipoprotein lipases exhibits a 35 -40% residue identity with a sub-region of Drosophilu vitellogenins. One fifth of the conserved amino acid residues (8 of 40) are glycine, a pattern which is typical of distantly related forms of protein families. This supports a true relationship between large segments of Drosophila vitellogenins and lipases. Physiological and functional aspects of the vitellogenin/lipoprotein lipase similarities are given. The region concerned is entirely within the N-terminal domain of lipoprotein lipase and constitutes the segment where the similarity to hepatic and pancreatic lipases is most pronounced. Within this lipase region a 10-residue putative lipid-binding site exists for which further similarities have been found to the otherwise not closely related lingual/gastric lipases, prokaryotic lipases and lecithin-cholesterol acyltransferase. Another segment in lipoprotein lipase, where the heparin-binding site has been mapped, exhibits a correlation between strength of heparin binding and extent of basic residues among members of the lipase family. It further exhibits weak similarities with the 'Zn-finger' DNA-binding segment of steroid hormone receptors and may indicate convergence in a binding interaction. Thus, a functional subdivision of lipoprotein lipase into different segments can be distinguished.

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Synthesis and Secretion of Hepatic Lipase by Rat Hepatocytes

Cited by 8 publications

References 11 publications

Endogenously Produced Endothelial Lipase Enhances Binding and Cellular Processing of Plasma Lipoproteins via Heparan Sulfate Proteoglycan-mediated Pathway

Endogenously Produced Endothelial Lipase Enhances Binding and Cellular Processing of Plasma Lipoproteins via Heparan Sulfate Proteoglycan-mediated Pathway

Annexin II inhibits calcium‐dependent phospholipase A₁ and lysophospholipase but not triacyl glycerol lipase activities of rat liver hepatic lipase

Structural features of lipoprotein lipase

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Synthesis and Secretion of Hepatic Lipase by Rat Hepatocytes

Cited by 8 publications

References 11 publications

Endogenously Produced Endothelial Lipase Enhances Binding and Cellular Processing of Plasma Lipoproteins via Heparan Sulfate Proteoglycan-mediated Pathway

Endogenously Produced Endothelial Lipase Enhances Binding and Cellular Processing of Plasma Lipoproteins via Heparan Sulfate Proteoglycan-mediated Pathway

Annexin II inhibits calcium‐dependent phospholipase A1 and lysophospholipase but not triacyl glycerol lipase activities of rat liver hepatic lipase

Structural features of lipoprotein lipase

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Product

Resources

About

Annexin II inhibits calcium‐dependent phospholipase A₁ and lysophospholipase but not triacyl glycerol lipase activities of rat liver hepatic lipase