Characterization of phosphomevalonate kinase: chromosomal localization, regulation, and subcellular targeting

Abstract

Phosphomevalonate kinase catalyzes the conversion of mevalonate-5-phosphate to mevalonate-5-diphosphate and was originally believed to be a cytosolic enzyme. In this study we have localized the phosphomevalonate kinase gene to chromosome 1p13-1q22-23 and present a genomic map indicating that the gene spans more than 8.4 kb in the human genome. Furthermore, we show that message levels and enzyme activity of rat liver phosphomevalonate kinase are regulated in response to dietary sterol levels and that this regulation is coordinate with 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme of cholesterol biosynthesis. In addition, we demonstrate that phosphomevalonate kinase is a peroxisomal protein which requires the C-terminal peroxisomal targeting signal, Ser-Arg-Leu, for localization to the organelle. -

Absence of functional peroxisomes does not lead to deficiency of enzymes involved in cholesterol biosynthesis

“…The first indication of peroxisomal involvement in the biosynthesis of isoprenoids came from immunoelectron microscopy studies by Keller and coworkers (13), who localized HMG-CoA reductase (RED) in rat liver peroxisomes. Further studies have indicated that also mevalonate kinase (MVK) (14), phosphomevalonate kinase (PMK) (15), mevalonate pyrophosphate decarboxylase (MPD) (16), isopentenyl pyrophosphate isomerase (IPPI) (17), and farnesyl pyrophosphate synthase (FPPS) (18,19) are (partly) peroxisomal. Additional indirect support for a peroxisomal localization came from the observation that several enzymes involved in cholesterol biosynthesis contain consensus peroxisomal targeting sequences (8).…”

Identification of peroxisomal targeting signals in cholesterol biosynthetic enzymes: AA-CoA thiolase, HMG-CoA synthase, MPPD, and FPP synthase

“…As mentioned previously, studies have indicated that a number of the enzymes involved in these reactions are localized to the peroxisomes. However, mechanisms for targeting to peroxisomes have been demonstrated only for PMvK and IPP isomerase (26,27). In the current study we identify the peroxisomal targeting signals required for four other enzymes of the cholesterol biosynthetic pathway: AA-CoA thiolase, HMG-CoA synthase, MPPD, and FPP synthase.…”

“…The human sequence for these amino acids is NS(DVYA)QE. In contrast, a comparison of human and rodent sequences for AA-CoA thiolase (28,40), HMG-CoA synthase (41,42), MvK (43,44), PMvK (26,45), MPPD (46,47), and IPP isomerase (27,48) reveals that the peroxisomal targeting signals are conserved. Therefore, this apparent lack of sequence conservation of FPP synthase between mammalian species might indicate that the sequence is not a specific receptor-binding site.…”

“…While the studies demonstrating activities of AA-CoA thiolase, HMG-CoA synthase, PMvK, MPPD, and IPP isomerase (11)(12)(13)(14)22) and the immunofluorescence and immunoelectron microscopy studies with MvK and FPP synthase (19,20,23) were suggestive of a peroxisomal localization of these enzymes, the specific peroxisomal targeting signals had yet to be identified. However, we have shown that PMvK contains a consensus PTS-1 (SRL), which is required for its localization to peroxisomes (26). Similarly, our group has shown that a Fig.…”

“…Expression vectors were transfected into cultured fibroblasts and processed for immunofluorescence as described (26). The Myc epitope was detected with a mouse anti-Myc antibody (purchased from InVitrogen) at 1:100 dilution, and the HA epitope was detected using a mouse anti-HA antibody at 1:100 dilution.…”