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

Thomas Eichmann, Lukas Grumet, Ulrike Taschler, Jürgen Hartler, Christoph Heier, Aaron Woblistin, Laura Pajed, Manfred Kollroser, Gerald Rechberger, Gerhard G. Thallinger, Rudolf Zechner, Guenter Haemmerle, Robert Zimmermann, Achim Lass

Research output: Contribution to journalArticle

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.
Original languageEnglish
Pages (from-to)1972-1984
JournalJournal of lipid research
Volume56
DOIs
Publication statusPublished - 2015

Fields of Expertise

  • Human- & Biotechnology

Treatment code (Nähere Zuordnung)

  • Basic - Fundamental (Grundlagenforschung)

Cooperations

  • BioTechMed-Graz

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