R. Kraemer et al., CHOLESTEROL ENRICHMENT ENHANCES EXPRESSION OF STEROL-CARRIER PROTEIN-2 - IMPLICATIONS FOR ITS FUNCTION IN INTRACELLULAR CHOLESTEROL TRAFFICKING, Journal of lipid research, 36(12), 1995, pp. 2630-2638
Cholesterol enrichment of vascular smooth muscle cells, as occurs unde
r conditions of hypercholesterolemia and atherosclerosis, is accompani
ed by specific changes in cholesterol metabolism and in intracellular
cholesterol trafficking. Sterol-carrier protein-2 (SCP2), an intracell
ular lipid binding protein, enhances the activation of enzymes involve
d in cholesterol metabolism. It may also enhance cholesterol efflux by
regulating the size of the ''fast'' cholesterol pool available for ef
flux to high density lipoproteins. However, a definitive role for SCP2
in arterial cholesterol metabolism is unclear. Therefore, we examined
the expression of SCP2 (13.1 kD), SCPx (58 kD), and p30 (30.8 kD) in
cultured arterial smooth muscle cells under conditions of cholesterol
enrichment. We found that SCP2, SCPx, and p30 are localized principall
y in the cytosolic fraction, with lesser amounts associated with the n
uclear/peroxisomal fraction; the expression of SCP2 protein and mRNA,
but not SCPx, is increased after exposure of smooth muscle cells to ca
tionized LDL. In contrast to the increased expression of SCP2, the exp
ression of p30 decreases after cholesterol enrichment of smooth muscle
cells. Coupled with previous studies demonstrating enhanced cholester
ol efflux from cholesterol-enriched smooth muscle cells in response to
high density lipoproteins, our results suggest that increased express
ion of SCP2 may partly mediate the cholesterol trafficking process.