The impact of nonpolar lipids on the regulation of the steryl ester hydrolases Tgl1p and Yeh1p in the yeast Saccharomyces cerevisiae

• Published in: Biochimica et biophysica acta. Molecular and cell biology of lipids 2017-12, Vol.1862 (12), p.1491-1501
• Main Authors: Klein, Isabella, Korber, Martina, Athenstaedt, Karin, Daum, Günther
• Format: Article
• Language: English
• Subjects: Carboxylic Ester Hydrolases - genetics; Carboxylic Ester Hydrolases - metabolism; Endoplasmic Reticulum - genetics; Endoplasmic Reticulum - metabolism; Hydrolase; Lipid droplets; Lipid Droplets - metabolism; Lipids; Membrane Lipids - genetics; Membrane Lipids - metabolism; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Sterol Esterase - genetics; Sterol Esterase - metabolism; Sterols; Steryl ester(s); Yeast
• ISSN: 1388-1981; 1879-2618
• DOI: 10.1016/j.bbalip.2017.08.009

In the yeast Saccharomyces cerevisiae degradation of steryl esters is catalyzed by the steryl ester hydrolases Tgl1p, Yeh1p and Yeh2p. The two steryl ester hydrolases Tgl1p and Yeh1p localize to lipid droplets, a cell compartment storing steryl esters and triacylglycerols. In the present study we investigated regulatory aspects of these two hydrolytic enzymes, namely the gene expression level, protein amount, stability and enzyme activity of Tgl1p and Yeh1p in strains lacking both or only one of the two major nonpolar lipids, steryl esters and triacylglycerols. In a strain lacking both nonpolar lipids and consequently lipid droplets, Tgl1p as well as Yeh1p were present at low amount, became highly unstable compared to wild-type cells, and lost their enzymatic activity. Under these conditions both steryl ester hydrolases were retained in the endoplasmic reticulum. The lack of steryl esters alone was not sufficient to cause an altered intracellular localization of Tgl1p and Yeh1p. Surprisingly, the stability of Tgl1p and Yeh1p was markedly reduced in a strain lacking triacylglycerols, but their capacity to mobilize steryl esters remained unaffected. We also tested a possible cross-regulation of Tgl1p and Yeh1p by analyzing the behavior of each hydrolase in the absence of its counterpart steryl ester hydrolases. In summary, this study demonstrates a strong regulation of the two lipid droplet associated steryl ester hydrolases Tgl1p and Yeh1p due to the presence/absence of their host organelle. •The two steryl ester hydrolases Tgl1p and Yeh1p are components of lipid droplets.•In a strain lacking lipid droplets Tgl1p-V5 and Yeh1p-V5 are retained in the ER.•The lack of the substrate of Tgl1p and Yeh1p has no impact on their subcellular localization.•Tgl1p-V5 and Yeh1p-V5 are highly unstable in a strain lacking lipid droplets.