Sterol carrier protein2 (SCP2)-like protein in rat aorta

: Immunoblot analysis using affinity-purified antibody against sterol carrier protein2 (SCP2) showed that SCP2-like protein exists in 105,000 x g supernatant of rat aorta. Analysis of subcellular distribution of SCP2-like protein in rat aorta was determined with enzyme immunoassay (EIA). The highest level of SCP2-like protein was observed in cytosolic fraction, while the lowest level was in nuclear fraction. Analysis of marker enzymes in subcellular fractions showed that catalase, a marker enzyme of peroxisomes, leaked to cytosolic fraction to a significant extent during subcellular preparation, suggesting that SCP2-like protein in cytosolic fraction of rat aorta might be partially originated from peroxisomes. In vitro addition of homogenous SCP2 purified from rat liver dose-dependently stimulated the formation of [14C]cholesteryl esters from exogenously added [14C]cholesterol by acyl-CoA:cholesterol acyltransferase (ACAT) in microsomal preparation of rat aorta. However the addition of cytosolic fraction did not enhance cholesterol esterification by ACAT, most likely due to a markedly low level of SCP2-like protein in this fraction. The role of SCP2 in the formation of cholesteryl esters by ACAT in rat aorta was discussed.