Expression of specific high capacity mevalonate transport in a Chinese hamster cell variant.
A variant of a low density lipoprotein receptor-negative Chinese hamster ovary (CHO) cell mutant was isolated using a nutritional selection called MeLoCo. The variant, designated met-18b-2, internalized and metabolized mevalonate at rates 10-40 times greater than the progenitor cells from which they were derived. The extent of incorporation of radioactivity from [3H]mevalonate into steroidal and nonsteroidal mevalonate derivatives, including modified proteins, was much greater in met-18b-2 cells than in their progenitors. Much of the internalized [3H]mevalonate was converted to nonpolar lipids. Unlike wild type CHO cells or the receptor-negative progenitors, met-18b-2 cells were killed by high concentrations of mevalonate (greater than 6 mM) in the culture medium. Regulation of 3-hydroxy-3-methylglutaryl-CoA reductase activity and cholesterol esterification was dramatically more sensitive to mevalonate in met-18b-2 cells than in progenitor cells. In cell extracts, both the rates of conversion of [3H]mevalonate to cholesterol and mevalonate kinase activities were similar for met-18b-2 and progenitor cells. In contrast to progenitor cells, met-18b-2 cells internalized [3H]mevalonate with high capacity (Km approximately 0.3 mM) kinetics. The increased uptake of [3H]mevalonate was temperature dependent and highly specific. These results suggest that met-18b-2 cells express a mevalonate transport activity that is not normally expressed by CHO cells. This activity may be due to a specific mevalonate transporter that is differentially expressed in specialized tissues. Because intracellular mevalonate in met-18b-2 cells can be labeled to high specific activity, these cells should prove very useful in further characterizing the structures of mevalonate derivatives and their metabolism.
D000818:Animals; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D005260:Female; D006888:Hydroxycholesterols / Q000494:pharmacology; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007700:Kinetics; D007810:Lanosterol / Q000378:metabolism; D008148:Lovastatin; D008798:Mevalonic Acid / Q000378:metabolism*; D009154:Mutation; D009281:Naphthalenes / Q000494:pharmacology; D010053:Ovary / Q000166:cytology / Q000378:metabolism*; D010641:Phenotype; D011973:Receptors, LDL / Q000172:deficiency; D013696:Temperature
D006888:Hydroxycholesterols; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D009281:Naphthalenes; D011973:Receptors, LDL; D007810:Lanosterol; C007997:25-hydroxycholesterol; D002784:Cholesterol; D008148:Lovastatin; D008798:Mevalonic Acid