Transfection of the ketogenic mitochondrial 3-hydroxy-3-methylglutaryl-coenzyme A synthase cDNA into Mev-1 cells corrects their auxotrophy for mevalonate.

A somatic cell mutant of the Chinese hamster ovary (CHO)-K1 (called Mev-1), auxotrophic for mevalonate by virtue of a complete lack of detectable cytosolic 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) synthase activity, was transfected with a plasmid containing the cDNA for ketogenic mitochondrial HMG-CoA synthase under the control of SV40 early promoter. The resulting stable cell line (Mev-SM) was able to grow in the absence of mevalonate. Analysis of Western blot showed that the new cell line strongly expressed mitochondrial HMG-CoA synthase protein. Immunocytochemical studies using specific antibodies against mitochondrial HMG-CoA synthase showed that the protein was located exclusively inside the mitochondria. The prototroph cell line Mev-SM can incorporate labeled acetate into cholesterol in the absence of mevalonate. These results show that the new cell line may circumvent the lack of cytosolic HMG-CoA synthase activity by producing cholesterol-convertible HMG-CoA inside the mitochondria.