Elevated cholesterol and decreased sterol carrier protein-2 in peroxisomes from AS-30D hepatoma compared to normal rat liver.
Peroxisomes were isolated from AS-30D hepatoma and compared to normal rat liver cells for the purpose of investigating the cholesterol accumulation in the hepatoma cells. Cholesterol was found to be approximately 10-fold higher relative to protein in AS-30D peroxisomes as compared to peroxisomes from normal liver. The peroxisomes from the hepatoma cells were found to be more stable; catalase was not released from these peroxisomes during isolation or osmotic shock of the peroxisomal fraction. The elevated cholesterol level may stabilize the peroxisomal membrane. Sterol carrier protein-2 (SCP-2) levels were measured using a radioimmunoassay (RIA), which indicated the highest concentration of SCP-2 to be in peroxisomes. Hepatoma peroxisomes had a lower concentration of SCP-2 (2.5 micrograms/mg) than normal liver peroxisomes (8 micrograms/mg). Approximately half of all SCP-2 detected was found to be soluble in both hepatoma and normal rat liver cells. Immunoblots from both rat liver and AS-30D fractions demonstrated the presence of the 14-kDa form of SCP-2. The liver fractions also had a 57-kDa immunoreactive protein, which was barely detectable in the AS-30D fractions. The low abundance of the high molecular weight form of SCP-2 from hepatoma peroxisomes and the lower amounts of SCP-2 detected in the AS-30D peroxisomes may be related to the accumulation of cholesterol in the cells.
Lyons
H T
HT
Department of Biological Sciences, George Washington University, Washington, D.C. 20052.
Kharroubi
A
A
Wolins
N
N
Tenner
S
S
Chanderbhan
R F
RF
Fiskum
G
G
Donaldson
R P
RP
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D002784:Cholesterol / Q000378:metabolism*; D005260:Female; D015151:Immunoblotting; D008099:Liver / Q000648:ultrastructure*; D008114:Liver Neoplasms, Experimental / Q000648:ultrastructure*; D008830:Microbodies / Q000201:enzymology / Q000378:metabolism*; D010940:Plant Proteins; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D010940:Plant Proteins; C072087:sterol carrier proteins; D002784:Cholesterol