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PMID:2307668

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Citation

Goldberg, IJ, Scheraldi, CA, Yacoub, LK, Saxena, U and Bisgaier, CL (1990) Lipoprotein ApoC-II activation of lipoprotein lipase. Modulation by apolipoprotein A-IV. J. Biol. Chem. 265:4266-72

Abstract

Lipoprotein lipase (LPL)-mediated hydrolysis of triglycerides (TG) contained in chylomicrons requires the presence of a cofactor, apolipoprotein (apo) C-II. The physiological mechanism by which chylomicrons gain apoC-II necessary for LPL activation in whole plasma is not known. Using a gum arabic stabilized TG emulsion, activation of LPL by lipoprotein apoC-II was studied. Hydrolysis of TG by LPL was greater in the presence of serum than with addition of either high density lipoproteins (HDL) or very low density lipoproteins (VLDL). LPL activation by either VLDL or HDL increased with addition of the lipoprotein-free fraction of plasma. A similar increase in LPL activity by addition of the lipoprotein-free fraction together with HDL or VLDL was observed when another TG emulsion (Intralipid) or TG-rich lipoproteins from an apoC-II deficient subject were used as a substrate. Human apoA-IV, apoA-I, apoE, and cholesteryl ester transfer protein were assessed for their ability to increase LPL activity in the presence of VLDL. At and below physiological concentrations, only apoA-IV increased LPL activity. One hundred percent of LPL activity measured in the presence of serum was achieved using VLDL plus apoA-IV. In the absence of an apoC-II source, apoA-IV had no effect on LPL activity. Removal of greater than 80% of the apoA-IV from the nonlipoprotein-containing fraction of plasma by incubation with Intralipid markedly reduced its ability to activate LPL in the presence of VLDL or HDL. Gel filtration chromatography demonstrated that incubation of the nonlipoprotein-containing fraction of plasma with HDL and the TG emulsion caused increased transfer of apoC-II to the emulsion and association of apoA-IV with HDL. Our studies demonstrate that apoA-IV increases LPL activation in the presence of lipoproteins. We hypothesize that apoA-IV is required for efficient release of apoC-II from either HDL or VLDL, which then allows for LPL-mediated hydrolysis of TG in nascent chylomicrons.

Links

PubMed

Keywords

Apolipoprotein C-II; Apolipoproteins A/pharmacology; Apolipoproteins C/pharmacology; Emulsions; Enzyme Activation/drug effects; Humans; Hydrolysis; Lipoprotein Lipase/metabolism; Lipoproteins, HDL/pharmacology; Lipoproteins, VLDL/pharmacology; Triglycerides/metabolism

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

HUMAN:APOA4

involved_in

GO:0045723: positive regulation of fatty acid biosynthetic process

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

HUMAN:APOA4

involved_in

GO:0034372: very-low-density lipoprotein particle remodeling

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

HUMAN:APOA4

involved_in

GO:0034371: chylomicron remodeling

ECO:0000305: curator inference used in manual assertion

GO:0051006

P

Seeded From UniProt

complete

HUMAN:APOA4

involved_in

GO:0010898: positive regulation of triglyceride catabolic process

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

HUMAN:APOA4

involved_in

GO:0051006: positive regulation of lipoprotein lipase activity

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete


See also

References

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