van Zutphen Tim, Todde Virginia, de Boer Rinse, Kreim Martin, Hofbauer Harald F, Wolinski Heimo, Veenhuis Marten, van der Klei Ida J, Kohlwein Sepp D
Molecular Cell Biology, University of Groningen, 9747 AG Groningen, Netherlands Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria.
Mol Biol Cell. 2014 Jan;25(2):290-301. doi: 10.1091/mbc.E13-08-0448. Epub 2013 Nov 20.
Cytosolic lipid droplets (LDs) are ubiquitous organelles in prokaryotes and eukaryotes that play a key role in cellular and organismal lipid homeostasis. Triacylglycerols (TAGs) and steryl esters, which are stored in LDs, are typically mobilized in growing cells or upon hormonal stimulation by LD-associated lipases and steryl ester hydrolases. Here we show that in the yeast Saccharomyces cerevisiae, LDs can also be turned over in vacuoles/lysosomes by a process that morphologically resembles microautophagy. A distinct set of proteins involved in LD autophagy is identified, which includes the core autophagic machinery but not Atg11 or Atg20. Thus LD autophagy is distinct from endoplasmic reticulum-autophagy, pexophagy, or mitophagy, despite the close association between these organelles. Atg15 is responsible for TAG breakdown in vacuoles and is required to support growth when de novo fatty acid synthesis is compromised. Furthermore, none of the core autophagy proteins, including Atg1 and Atg8, is required for LD formation in yeast.
胞质脂滴（LDs）是原核生物和真核生物中普遍存在的细胞器，在细胞和机体脂质稳态中起关键作用。储存在脂滴中的三酰甘油（TAGs）和甾醇酯通常在生长中的细胞中或在激素刺激下，由与脂滴相关的脂肪酶和甾醇酯水解酶动员。在这里，我们表明，在酿酒酵母中，脂滴也可以通过一种形态上类似于微自噬的过程在液泡/溶酶体中被周转。我们鉴定出了一组参与脂滴自噬的独特蛋白质，其中包括核心自噬机制，但不包括Atg11或Atg20。因此，尽管这些细胞器之间联系紧密，但脂滴自噬与内质网自噬、过氧化物酶体自噬或线粒体自噬不同。Atg15负责液泡中TAG的分解，并且在从头脂肪酸合成受损时是支持生长所必需的。此外，包括Atg1和Atg8在内的核心自噬蛋白都不是酵母中脂滴形成所必需的。
