Oxysterol-binding protein 1 (OSBP)

Lipid transporter involved in lipid countertransport between the Golgi complex and membranes of the endoplasmic reticulum: namely exchanges sterol with phosphatidylinositol 4-phosphate (PI4P), delivering sterol to the Golgi in exchange for PI4P, which can be degraded by the SAC1/SACM1L phosphatase in the endoplasmic reticulum (PubMed:24209621). Binds cholesterol and a range of oxysterols such as 25-hydroxycholesterol (PubMed:15746430, PubMed:17428193).

Cholesterol binding promotes the formation of a complex with PP2A and a tyrosine phosphatase that dephosphorylates ERK1/2, whereas 25-hydroxycholesterol induces its disassembly (PubMed:15746430). Regulates cholesterol efflux by decreasing ABCA1 equilibrium (PubMed:18450749).