Differential translational effects of myristic acid and eicosapentaenoic acid on 3-hydroxy-3-methylglutaryl-CoA reductase from Reuber H35 hepatoma cells.
The mechanisms by which saturated and polyunsaturated fatty acids may exert their effects on levels of blood cholesterol and human atherosclerosis have not been fully established. In this work, we studied the translational effects of myristic (14:0) and eicosapentaenoic (20:5) acids on 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase from Reuber H35 hepatoma cells. This enzyme is an intrinsic membrane, 96-kDa protein whose proteolysis releases an enzymatically active, 52- to 56-kDa, soluble fragment. We optimized an immunoblot procedure for quantifying small amounts of both the native and the soluble forms of HMG-CoA reductase from Reuber H35 hepatoma cells. We demonstrated that the upregulation of HMG-CoA reductase by a acid is due to an increase of the HMG-CoA reductase protein; therefore, protein synthesis would be required for the increase of HMG-CoA reductase activity caused by this fatty acid. In contrast, the downregulation of HMG-CoA reductase caused by eicosapentaenoic acid is not due to decreased protein synthesis, since similar levels of protein were found in the presence and absence of this fatty acid. Results obtained with cycloheximide as a protein-synthesis inhibitor confirm these findings.
García-Pelayo
M Carmen
MC
Department of Biochemistry and Molecular Biology, University of Granada, Polígono de Cartuja s/n, 18071 Granada, Spain.
García-Peregrín
Eduardo
E
Martínez-Cayuela
Marina
M
D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006903:Hydroxymethylglutaryl CoA Reductases / Q000235:genetics*; D008113:Liver Neoplasms; D019814:Myristic Acid; D014176:Protein Biosynthesis / Q000187:drug effects*; D051381:Rats
D001095:Arachidonic Acids; D019814:Myristic Acid; D006903:Hydroxymethylglutaryl CoA Reductases