Sørensen DM, Holen HW, Pedersen JT, Martens HJ, Silvestro D, Stanchev LD, Costa SR, Günther Pomorski T, López-Marqués RL, Palmgren M. The P5A ATPase Spf1p is stimulated by phosphatidylinositol 4-phosphate and influences cellular sterol homeostasis.
Mol Biol Cell 2019;
30:1069-1084. [PMID:
30785834 PMCID:
PMC6724510 DOI:
10.1091/mbc.e18-06-0365]
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Abstract
P5A ATPases are expressed in the endoplasmic reticulum (ER) of all eukaryotic cells, and their disruption results in severe ER stress. However, the function of these ubiquitous membrane proteins, which belong to the P-type ATPase superfamily, is unknown. We purified a functional tagged version of the Saccharomyces cerevisiae P5A ATPase Spf1p and observed that the ATP hydrolytic activity of the protein is stimulated by phosphatidylinositol 4-phosphate (PI4P). Furthermore, SPF1 exhibited negative genetic interactions with SAC1, encoding a PI4P phosphatase, and with OSH1 to OSH6, encoding Osh proteins, which, when energized by a PI4P gradient, drive export of sterols and lipids from the ER. Deletion of SPF1 resulted in increased sensitivity to inhibitors of sterol production, a marked change in the ergosterol/lanosterol ratio, accumulation of sterols in the plasma membrane, and cytosolic accumulation of lipid bodies. We propose that Spf1p maintains cellular sterol homeostasis by influencing the PI4P-induced and Osh-mediated export of sterols from the ER.
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