Lipid transporter involved in lipid countertransport between the endoplasmic reticulum and the plasma membrane: specifically exchanges phosphatidylserine with phosphatidylinositol 4-phosphate (PI4P), delivering phosphatidylserine to the plasma membrane in exchange for PI4P, which is degraded by the SAC1/SACM1L phosphatase in the endoplasmic reticulum. Binds phosphatidylserine and PI4P in a mutually exclusive manner (, ). May cooperate with NPC1 to mediate the exit of cholesterol from endosomes/lysosomes . Binds 25-hydroxycholesterol and cholesterol .
Subcellular locations: Endoplasmic reticulum membrane
Localizes to endoplasmic reticulum-plasma membrane contact sites (EPCS). Localizes to the cortical endoplasmic reticulum at the EPCS.
Ubiquitously expressed.