ATGL and CGI-58 are lipid droplet proteins of the hepatic stellate cell line HSC-T6.
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.
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Thomas O
TO
Eichmann
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Lukas
L
Grumet
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Ulrike
U
Taschler
Bioinformatics, Institute for Knowledge Discovery, Graz University of Technology, Graz, Austria.
Jürgen
J
Hartler
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Christoph
C
Heier
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Aaron
A
Woblistin
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Laura
L
Pajed
Institute of Forensic Medicine, Medical University of Graz, Graz, Austria.
Manfred
M
Kollroser
Institute of Molecular Biosciences, University of Graz, Graz, Austria BioTechMed-Graz, Graz, Austria OMICS Center, Graz, Austria.
Gerald
G
Rechberger
Bioinformatics, Institute for Knowledge Discovery, Graz University of Technology, Graz, Austria BioTechMed-Graz, Graz, Austria OMICS Center, Graz, Austria.
Gerhard G
GG
Thallinger
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Rudolf
R
Zechner
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Günter
G
Haemmerle
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Robert
R
Zimmermann
Institute of Molecular Biosciences, University of Graz, Graz, Austria.
Achim
A
Lass
D000217:Acyltransferases / Q000378:metabolism*; D017667:Adipocytes / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D055166:Hepatic Stellate Cells / Q000378:metabolism*; D008049:Lipase / Q000378:metabolism*; D066292:Lipid Droplets / Q000378:metabolism*; D008066:Lipolysis; D008074:Lipoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D000070780:Perilipin-2; D020543:Proteome / Q000378:metabolism; D051381:Rats; D012177:Retinol-Binding Proteins / Q000378:metabolism; D000084562:Retinyl Esters; D014280:Triglycerides / Q000378:metabolism; D014801:Vitamin A / Q000494:pharmacology
C520594:Abhd5 protein, rat; D008074:Lipoproteins; D008565:Membrane Proteins; D000070780:Perilipin-2; D020543:Proteome; D012177:Retinol-Binding Proteins; D000084562:Retinyl Esters; D014280:Triglycerides; C022081:retinyl ester lipoprotein complex; D014801:Vitamin A; D000217:Acyltransferases; D008049:Lipase; C571275:PNPLA2 protein, rat
adipose triglyceride lipase; lipidome; neutral lipid hydrolase; proteome