Probable lipid transporter involved in lipid countertransport between the endoplasmic reticulum and the plasma membrane. Its ability to bind phosphatidylserine, suggests that it specifically exchanges phosphatidylserine with phosphatidylinositol 4-phosphate (PI4P), delivering phosphatidylserine to the plasma membrane in exchange for PI4P. Plays a role in negative regulation of lipid biosynthesis. Negatively regulates APOB secretion from hepatocytes. Binds cholesterol and acidic phospholipids. Also binds 25-hydroxycholesterol. Binds phosphatidylserine. Interacts with OSBPL9. Interacts with DIAPH1. Associates with microtubules. The C-terminal region binds cholesterol, 25-hydroxysterol and acidic phospholipids and is required for localization to microtubules. The PH domain selectively interacts with phosphatidylinositol-4-phosphate.