Oxysterol-binding protein 1 (OSBP) is involved in lipid countertransport between the Golgi and the ER membranes. It specifically exchanges sterols such as 25-hydroxycholesterol (25OH-CHOL) with phosphatidylinositol 4-phosphate (PI4P), delivering it to the Golgi in exchange for PI4P, which is degraded by the SAC1/SACM1L phosphatases in the ER. The PH-FFAT region of OSBP is necessary for membrane tethering, which then directs forward sterol and backward PI4P transport by the ORD domain of OSBP (Mesmin et al. 2013).
Moser von Filseck, J, Lacas-Gervais, S, Bigay, J, Drin, G, Mesmin, B, Antonny, B
sterol transporter activity of OSBP [cytosol]
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