Localization of Lipid Raft Proteins to the Plasma Membrane Is a Major Function of the Phospholipid Transfer Protein Sec14

Abstract

The Sec14 protein domain is a conserved tertiary structure that binds hydrophobic ligands. The Sec14 protein from Saccharomyces cerevisiae is essential with studies of S. cerevisiae Sec14 cellular function facilitated by a sole temperature sensitive allele, sec14ts. The sec14ts allele encodes a protein with a point mutation resulting in a single amino acid change, Sec14G266D. In this study results from a genome-wide genetic screen, and pharmacological data, provide evidence that the Sec14G266D protein is present at a reduced level compared to wild type Sec14 due to its being targeted to the proteosome. Increased expression of the sec14ts allele ameliorated growth arrest, but did not restore the defects in membrane accumulation or vesicular transport known to be defective in sec14ts cells. We determined that trafficking and localization of two well characterized lipid raft resident proteins, Pma1 and Fus-Mid-GFP, were aberrant in sec14ts cells. Localization of both lipid raft proteins was restored upon increased expression of the sec14ts allele. We suggest that a major function provided by Sec14 is trafficking and localization of lipid raft proteins. © 2013 Curwin et al.