Identification and Characterization of Genetic Variation in the Folylpolyglutamate Synthase Gene

Abstract

Folylpolyglutamate synthase (FPGS) catalyzes the polyglutamation of folic acid, methotrexate, and pemetrexed to produce highly active metabolites. To characterize genetic variation in the FPGS gene, FPGS, have resequenced the gene in four different ethnic populations. Thirty-four single nucleotide polymorphisms were identified including five nonsynonymous coding single nucleotide polymorphisms that altered the FPGS protein sequence: F13L and V22I polymorphisms in the mitochondrial isoform of FPGS, and R466/424C, A489/ 447V, and S499/457F polymorphisms, which exist in both the mitochondrial and cytosolic isoforms. When expressed in AuxB1 cells, the A447V cytosolic variant was functionally similar to the wild-type cytosolic (WT Cyt) allozyme, whereas the R424C and S457F cytosolic variants were reduced by f2-fold in protein expression compared with WT Cyt (P < 0.01). The intrinsic clearance of glutamate was reduced by 12.3-fold (R424C, P < 0.01) and 6.2-fold (S457F, P < 0.01), whereas the intrinsic clearance of methotrexate was reduced by 4.2-fold (R424C, P < 0.05) and 5.4-fold (S457F, P < 0.05) in these two cytosolic variants when compared with the WT Cyt isoform. Additionally, the in vitro enzyme velocity at saturating pemetrexed concentrations was reduced by 1.6-fold (R424C, P < 0.05) and 2.6-fold (S457F, P < 0.01) compared with WT Cyt. AuxB1 cells harboring these same cytosolic variant allozymes displayed significant increases in the EC 50 for folic acid and in the IC 50 values for both methotrexate and pemetrexed relative to the WT Cyt form of FPGS. These observations suggest that genetic variations in FPGS may alter the efficacy of antifolate therapy in cancer patients. [Cancer Res 2007;67(18):8772-82]

Folate Biosynthesis - Reappraisal of Old and Novel Targets in the Search for New Antimicrobials

“…Although the sequence similarity is high between FPGS and DHFS, there is a growing body of structural evidence to suggest that it may well be feasible to design selective inhibitors against DHFS at least. FPGS may represent a potential target in its own right; compounds targeting FPGS may have utility in preventing cell proliferation and cancers [126][127][128][129][130]. Fig.…”

Warfarin pharmacogenetics: it matters if you’re black or white

“…1 FPGS catalyses the polyglutamation of folic acid and of certain antifolate drugs, 10 but its connection with warfarin is unknown. The rs7856096 variant is common in African Americans with an allele frequency of ;20%, which is why it has the potential to be important in this population.…”

Exosome complex and erythropoiesis

“…However, thrombocytosis was observed in 2 mouse models with decreased Mpl expression on differentiated megakaryocytes and platelets as a first hint that the main function of Mpl on megakaryocytes and platelets could be to down-regulate Tpo availability. 9,10 The studies by Ng et al and Meyer et al both use Pf4-Cre mice, which express the Cre-recombinase primarily in megakaryocytes and platelets, allowing lineage-specific deletion of conditional alleles during late megakaryocyte maturation but preserving expression in HSCs and progenitors. Both studies now firmly demonstrate that the absence of Mpl and Jak2 in megakaryocytes and platelets does not interfere with terminal differentiation and platelet formation.…”