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J Lipid Res. 2015 Oct;56(10):1972-84. doi: 10.1194/jlr.M062372. Epub 2015 Aug 31.

ATGL and CGI-58 are lipid droplet proteins of the hepatic stellate cell line HSC-T6.

Author information

1
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
2
Bioinformatics, Institute for Knowledge Discovery, Graz University of Technology, Graz, Austria.
3
Institute of Forensic Medicine, Medical University of Graz, Graz, Austria.
4
Institute of Molecular Biosciences, University of Graz, Graz, Austria BioTechMed-Graz, Graz, Austria OMICS Center, Graz, Austria.
5
Bioinformatics, Institute for Knowledge Discovery, Graz University of Technology, Graz, Austria BioTechMed-Graz, Graz, Austria OMICS Center, Graz, Austria.

Abstract

Lipid droplets (LDs) of hepatic stellate cells (HSCs) contain large amounts of vitamin A [in the form of retinyl esters (REs)] as well as other neutral lipids such as TGs. During times of insufficient vitamin A availability, RE stores are mobilized to ensure a constant supply to the body. To date, little is known about the enzymes responsible for the hydrolysis of neutral lipid esters, in particular of REs, in HSCs. In this study, we aimed to identify LD-associated neutral lipid hydrolases by a proteomic approach using the rat stellate cell line HSC-T6. First, we loaded cells with retinol and FAs to promote lipid synthesis and deposition within LDs. Then, LDs were isolated and lipid composition and the LD proteome were analyzed. Among other proteins, we found perilipin 2, adipose TG lipase (ATGL), and comparative gene identification-58 (CGI-58), known and established LD proteins. Bioinformatic search of the LD proteome for α/β-hydrolase fold-containing proteins revealed no yet uncharacterized neutral lipid hydrolases. In in vitro activity assays, we show that rat (r)ATGL, coactivated by rat (r)CGI-58, efficiently hydrolyzes TGs and REs. These findings suggest that rATGL and rCGI-58 are LD-resident proteins in HSCs and participate in the mobilization of both REs and TGs.

KEYWORDS:

adipose triglyceride lipase; lipidome; neutral lipid hydrolase; proteome

PMID:
26330055
PMCID:
PMC4583087
DOI:
10.1194/jlr.M062372
[Indexed for MEDLINE]
Free PMC Article
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