The present invention relates to nucleic acids encoding peripheral-type benzodiazepine receptor (PBR)-associated proteins (PAPs), and nucleic acids that hybridize or are variant of nucleic acids encoding the peripheral-type benzodiazepine receptor (PBR)-associated proteins (PAPs), which are capable of encoding proteins that regulate the function of PBRs affecting both steroid biosynthesis and mediating cholesterol delivery as well as other PBR-mediated functions.