OSBP and OSBPL1–11/ORP1–11
During early studies on the regulation of cellular cholesterol homeostasis, oxysterols such as 25-hydroxycholesterol (25-OHC) were found to potently reduce the activity of HMGCoA reductase, a rate-limiting enzyme in cholesterol biosynthesis. These findings motivated search for proteins mediating the effects of oxysterols on cholesterol homeostatic machinery, resulting in the isolation of protein fractions with oxysterol-binding activity. Taylor, Kandutsch, and coworkers identified in the 1980s a cytosolic oxysterol-binding protein (OSBP), which was purified (Taylor et al. 1984; Dawson et al. 1989), and cDNAs were cloned from different species....