cDNA cloning of MEV, a mutant protein that facilitates cellular uptake of mevalonate, and identification of the point mutation responsible for its gain of function

Abstract

We report the expression cloning of pMev, a cDNA that facilitates cellular uptake of mevalonate. pMev was isolated from the met-18b-2 clone of Chinese hamster ovary (CHO) cells, which were selected for growth in low concentrations of mevalonate when synthesis is blocked by compactin (Faust, J. R., and Krieger, M. (1987) J. Biol. Chem. 262, 1996-2004). pMev encodes a 494-residue protein, Mev, that is predicted to have 12 membrane-spanning regions, consistent with a membrane transporter. Surprisingly, levels of Mev mRNA and protein are similar in CHO and met-18b-2 cells. The Mev gene differs from the wild-type gene by a single base change that substitutes a cysteine for phenylalanine in the 10th membrane-spanning region. met-18b-2 cells are heterozygous for this dominant gain-of-function mutation. Transfection of a cDNA encoding pMev, but not the wild-type cDNA, elicited a marked increase in [3H]mevalonate uptake and incorporation into cellular lipids in stably and transiently transfected cells. The availability of pMev will facilitate studies of [3H]mevalonate incorporation into trace products, including p21ras and other prenylated proteins.