Lipid droplet dynamics in budding yeast

Abstract

Eukaryotic cells store excess fatty acids as neutral lipids, predominantly triacylglycerols and sterol esters, in organelles termed lipid droplets (LDs) that bulge out from the endoplasmic reticulum. LDs are highly dynamic and contribute to diverse cellular functions. The catabolism of the storage lipids within LDs is channeled to multiple metabolic pathways, providing molecules for energy production, membrane building blocks, and lipid signaling. LDs have been implicated in a number of protein degradation and pathogen infection processes. LDs may be linked to prevalent human metabolic diseases and have marked potential for biofuel production. The knowledge accumulated on LDs in recent years provides a foundation for diverse, and even unexpected, future research. This review focuses on recent advances in LD research, emphasizing the diverse physiological roles of LDs in the model system of budding yeast.

Fig. 1

The formation of LD. a LD composition. b A simple model of LD formation and growth. Yeast contains four neutral lipid synthesis enzymes. Are1 and Are2 catalyze the synthesis of sterol ester (SE), while Dga1 and Lro1 catalyze the synthesis of triacylglycerol (TAG). Neutral lipids accumulated within the ER bilayer on reaching a critical threshold form lens, and subsequently a nascent LD buds into the cytoplasm. LDs can grow by recruiting Dga1 to the surface of LDs for TAG synthesis

Fig. 2

The metabolic pathways of SE and TAG in S. cerevisiae (adopted from Rajakumari et al. [26] and Currie et al. [105]). Enzymes are indicated in blue. Cyan zone formation of SE. Green zone formation of TAG. Yellow zone formation of FA-CoA. Red zone formation of phospholipids. FA fatty acid, CoA coenzyme A, FA-CoA fatty acyl-CoA, DHAP dihydroxyacetone phosphate, lyso-PA 1-acylglycerol-3-phosphate, PA phosphatidic acid, DAG diacylglycerol, CDP-DAG cytidine diphosphate-diacylglycerol, Ino inositol, PI phosphatidylinositol, PS phosphatidylserine, PE phosphatidylethanolamine, PC phosphatidylcholine, CDP-Eth cytidine diphosphate-ethanolamine, CDP-Cho cytidine diphosphate-choline, Eth ethanolamine, Cho choline, MAG monoacylglycerol, CTP cytidine triphosphate, Pi inorganic phosphate