Sphingolipids with Very Long-chain Fatty Acids Regulate Vacuole Fusion During Tethering and Docking

Abstract

AbstractThe role of sphingolipids in controlling the endolysosomal membrane trafficking remains unclear. Here, we show that inSaccharomyces cerevisiaesphingolipids containing very long-chain fatty-acids (VLCAs) promote homotypic vacuolar fusion. Yeast that lack the C26 VLCA elongase Elo3p display morphological and vacuolar abnormalities. Vacuoles isolated from these cells displayed reduced levels ofin vitrofusion, which we traced to a block in tethering and docking. We found that C26 VLCFA deficient yeast mislocalize fusion markers, and the small GTPases Rho1p and Ypt7p fail to selectively concentrate at the boundary and vertex domains of vacuoles isolated from these yeasts. Surprisingly, we only observed mild changes to the localization of other regulatory lipids, but membrane fluidity and solubility was significantly altered. Taken together, these results suggest that sphingolipids containing C26 VLCFAs act as regulatory lipids in the homotypic vacuolar fusion cascade by assembling membrane microdomains that promote the protein and lipid machinery required for the tethering and docking of vacuoles.SummaryMany sphingolipids contain very-long chain fatty-acids with 26 carbons. The deletion of Elo3, the elongase that adds the final two carbons results in pleiotropic effects that negatively alter membrane fusion at the tethering and docking stages.