Players in the Nonpolar Lipid Game: Proteins Involved in Nonpolar Lipid Metabolism in Yeast
Synthesis, storage, and degradation of nonpolar lipids enable cells to continue cell metabolism when nutrients are no longer provided by the environment. Major nonpolar lipids occurring in yeast are triacylglycerols and steryl esters. These hydrophobic molecules are sequestered from the cytosolic environment in the core of special organelles termed lipid droplets (lipid particles). When nutrients are no longer provided by the environment, hydrolytic enzymes catalyze the degradation of triacylglycerols and steryl esters. The respective breakdown products serve as energy source and/or building blocks for membrane formation. Here, enzymes catalyzing nonpolar lipid synthesis and degradation in the budding yeast Saccharomyces cerevisiae are described with special emphasis to their localization and regulation. Furthermore, examples are presented showing that the formation of lipid droplets is not only disturbed in cells defective in polypeptides directly involved in nonpolar lipid synthesis and degradation, but also in a number of mutants defective in polypeptides and pathways which are not obviously linked to nonpolar lipid turnover. Although research over the past decade provided major insights into nonpolar lipid metabolism, many aspects of nonpolar lipid synthesis, storage, and degradation remain to be elucidated. Research needs for a better understanding of nonpolar lipid turnover are outlined at the end of this chapter.
This work was financially supported by the Austrian Science Fund (FWF) project P26308 to K.A.
- Choudhary V, Jacquier N, Schneiter R (2011) The topology of the triacylglycerol synthesizing enzyme Lro1 indicates that neutral lipids can be produced within the luminal compartment of the endoplasmatic reticulum: implications for the biogenesis of lipid droplets. Commun Integr Biol 4:781–784CrossRefGoogle Scholar
- Ghosal A, Banaś A, Ståhl U, Dahlqvist A, Lindqvist Y, Stymne S (2007) Saccharomyces cerevisiae phospholipid:diacylglycerol acyl transferase (PDAT) devoid of its membrane anchor region is a soluble and active enzyme retaining its substrate specificities. Biochim Biophys Acta 1771:1457–1463CrossRefGoogle Scholar
- Ståhl U, Carlsson AS, Lenman M, Dahlqvist A, Wiberg E, Banaś W, Banaś A, Stymne S (2004) Cloning and characterization of a phospholipid:diacylglycerol acyltransferase from Arabidopsis. Plant Physiol 135:1324–1335Google Scholar
- Wolinski H, Hofbauer HF, Hellauer K, Cristobal-Sarramian A, Kolb D, Radulovic M, Knittelfelder OL, Rechberger GN, Kohlwein SD (2015) Seipin is involved in the regulation of phosphatidic acid metabolism at a subdomain of the nuclear envelope in yeast. Biochim Biophys Acta 1851:1450–1464CrossRefGoogle Scholar