Format

Send to

Choose Destination
Biochem Biophys Res Commun. 2013 Nov 29;441(4):941-6. doi: 10.1016/j.bbrc.2013.11.013. Epub 2013 Nov 9.

Inactivation of lipoprotein lipase in 3T3-L1 adipocytes by angiopoietin-like protein 4 requires that both proteins have reached the cell surface.

Author information

1
Department of Medical Biosciences, Physiological Chemistry, Umeå University, SE-901 87 Umeå, Sweden.

Abstract

Lipoprotein lipase (LPL) and angiopoietin-like protein 4 (Angptl4) were studied in 3T3-L1 adipocytes. Transfections of the adipocytes with Angptl4 esiRNA caused reduction of the expression of Angptl4 to about one fourth of that in cells treated with vehicle only. This resulted in higher levels of LPL activity both on cell surfaces (heparin-releasable) and in the medium, while LPL activity within the cells remained unaffected. This demonstrated that even though both proteins are made in the same cell, Angptl4 does not inactivate LPL during intracellular transport. Most of the Angptl4 protein was present as covalent dimers and tetramers on cell surfaces, while within the cells there were only monomers. LPL gradually lost activity when incubated in medium, but there was no marked difference between conditioned medium from normal cells (rich in Angptl4) and medium after knockdown of Angptl4. Hence Angptl4 did not markedly accelerate inactivation of LPL in the medium. Experiments with combinations of different cells and media indicated that inactivation of LPL occurred on the surfaces of cells producing Angptl4.

KEYWORDS:

10mM phosphate, 0.15M NaCl, pH 7.4; 3-Isobutyl-1-methylxantine; 3T3-L1; Adipocytes; Angiopoietin-like protein 4; Angptl4; BSA; DEX; DMEM; Dulbecco’s modified Eagle’s medium; HI-FCS; Heparin-releasable; LPD; LPL; Lipoprotein lipase; MIX; PBS; RNAi; angiopoietin-like protein 4; bovine serum albumin; dexamethasone; endoribonuclease-prepared siRNA pools comprised of a heterogeneous mixture of siRNAs that all target the same mRNA sequence; esiRNA; heat-inactivated fetal calf serum; lipoprotein lipase; lipoprotein-deficient

PMID:
24220340
DOI:
10.1016/j.bbrc.2013.11.013
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center