The Saccharomyces cerevisiae YLL012/YEH1, YLR020/YEH2, and TGL1 genes encode a novel family of membrane-anchored lipases that are required for steryl ester hydrolysis.
Sterol homeostasis in eukaryotic cells relies on the reciprocal interconversion of free sterols and steryl esters. The formation of steryl esters is well characterized, but the mechanisms that control steryl ester mobilization upon cellular demand are less well understood. We have identified a family of three lipases of Saccharomyces cerevisiae that are required for efficient steryl ester mobilization. These lipases, encoded by YLL012/YEH1, YLR020/YEH2, and TGL1, are paralogues of the mammalian acid lipase family, which is composed of the lysosomal acid lipase, the gastric lipase, and four novel as yet uncharacterized human open reading frames. Lipase triple-mutant yeast cells are completely blocked in steryl ester hydrolysis but do not affect the mobilization of triacylglycerols, indicating that the three lipases are required for steryl ester mobilization in vivo. Lipase single mutants mobilize steryl esters to various degrees, indicating partial functional redundancy of the three gene products. Lipase double-mutant cells in which the third lipase is expressed from the inducible GAL1 promoter have greatly reduced steady-state levels of steryl esters, indicating that overexpression of any of the three lipases is sufficient for steryl ester mobilization in vivo. The three yeast enzymes constitute a novel class of membrane-anchored lipases that differ in topology and subcellular localization.
Köffel
René
R
University of Fribourg, Department of Medicine, Division of Biochemistry, Chemin du Musée 5, CH-1700 Fribourg, Switzerland.
Tiwari
Rashi
R
Falquet
Laurent
L
Schneiter
Roger
R
D000595:Amino Acid Sequence; D002265:Carboxylic Ester Hydrolases / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000737:chemistry / Q000201:enzymology; D004952:Esters / Q000378:metabolism; D005800:Genes, Fungal / Q000502:physiology; D006801:Humans; D006868:Hydrolysis; D008563:Membrane Lipids / Q000378:metabolism*; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D002787:Sterol Esterase; D013261:Sterols / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
D004952:Esters; D008563:Membrane Lipids; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; D013261:Sterols; D014280:Triglycerides; D002265:Carboxylic Ester Hydrolases; C498187:TGL1 protein, S cerevisiae; D002787:Sterol Esterase; C498185:YEH1 protein, S cerevisiae; C498186:YEH2 protein, S cerevisiae