Control of Endocytic Trafficking and Recycling Pathways by Phosphatidylserine in S. cerevisiae

Abstract

Phosphatidylserine (PS) is the most abundant anionic phospholipid in cells. Consequently, it plays important roles in intracellular function, including in the endocytic trafficking pathway. Specifically, PS is involved in retrograde transport pathways that facilitate recycling from endosomes to the trans Golgi network (TGN). The role of PS in retrograde transport from early endosomes to TGN has been studied in some detail, however, its role in transport from late endosomes to TGN, a pathway mediated by the retromer complex, has been less well studied. This work characterizes the effects of PS-deficiency in S. cerevisiae on proteins involved in retrograde transport from late endosomes to the TGN. Protein localization data show that the retromer system is dysfunctional in PS-deficient cells. Additionally, PS transport and distribution in the cell is largely mediated by the lipid transfer proteins, Osh6 and Osh7. This work characterises the effects of Osh6 and Osh7 on PS distribution and metabolism and shows that there are compensatory mechanisms for distributing PS.