title: Pharmacologic rescue of an enzyme-trafficking defect in primary hyperoxaluria 1.
abstract: Primary hyperoxaluria 1 (PH1; Online Mendelian Inheritance in Man no. 259900), a typically lethal biochemical disorder, may be caused by the AGT(P11LG170R) allele in which the alanine:glyoxylate aminotransferase (AGT) enzyme is mistargeted from peroxisomes to mitochondria. AGT contains a C-terminal peroxisomal targeting sequence, but mutations generate an N-terminal mitochondrial targeting sequence that directs AGT from peroxisomes to mitochondria. Although AGT(P11LG170R) is functional, the enzyme must be in the peroxisome to detoxify glyoxylate by conversion to alanine; in disease, amassed glyoxylate in the peroxisome is transported to the cytosol and converted to oxalate by lactate dehydrogenase, leading to kidney failure. From a chemical genetic screen, we have identified small molecules that inhibit mitochondrial protein import. We tested whether one promising candidate, Food and Drug Administration (FDA)-approved dequalinium chloride (DECA), could restore proper peroxisomal trafficking of AGT(P11LG170R). Indeed, treatment with DECA inhibited AGT(P11LG170R) translocation into mitochondria and subsequently restored trafficking to peroxisomes. Previous studies have suggested that a mitochondrial uncoupler might work in a similar manner. Although the uncoupler carbonyl cyanide m-chlorophenyl hydrazone inhibited AGT(P11LG170R) import into mitochondria, AGT(P11LG170R) aggregated in the cytosol, and cells subsequently died. In a cellular model system that recapitulated oxalate accumulation, exposure to DECA reduced oxalate accumulation, similar to pyridoxine treatment that works in a small subset of PH1 patients. Moreover, treatment with both DECA and pyridoxine was additive in reducing oxalate levels. Thus, repurposing the FDA-approved DECA may be a pharmacologic strategy to treat PH1 patients with mutations in AGT because an additional 75 missense mutations in AGT may also result in mistrafficking.
authors.affiliation: Department of Chemistry and Biochemistry.
authors.forename: Non
authors.initials: N
authors.lastname: Miyata
authors.affiliation: Department of Chemistry and Biochemistry.
authors.forename: Janos
authors.initials: J
authors.lastname: Steffen
authors.affiliation: Department of Chemistry and Biochemistry.
authors.forename: Meghan E
authors.initials: ME
authors.lastname: Johnson
authors.affiliation: Department of Cell and Developmental Biology, Division of Biosciences, University College London, London WC1E 6BT, United Kingdom.
authors.forename: Sonia
authors.initials: S
authors.lastname: Fargue
authors.affiliation: Department of Cell and Developmental Biology, Division of Biosciences, University College London, London WC1E 6BT, United Kingdom.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Danpure
authors.affiliation: Department of Chemistry and Biochemistry, Molecular Biology Institute, and Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA 90095; and koehler@chem.ucla.edu.
authors.forename: Carla M
authors.initials: CM
authors.lastname: Koehler
mesh_terms: D000818:Animals; D000891:Anti-Infective Agents, Local / Q000494:pharmacology; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003868:Dequalinium / Q000494:pharmacology*; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000196:embryology; D006801:Humans; D006960:Hyperoxaluria, Primary / Q000235:genetics / Q000378:metabolism* / Q000517:prevention & control; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D009154:Mutation; D010070:Oxalates / Q000378:metabolism; D020675:Peroxisomes / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics; D011736:Pyridoxine / Q000494:pharmacology; D000637:Transaminases / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology
chemical_list: D000891:Anti-Infective Agents, Local; D010070:Oxalates; D003868:Dequalinium; D000637:Transaminases; C019635:Alanine-glyoxylate transaminase; D011736:Pyridoxine