title: CYP4V2 in Bietti's crystalline dystrophy: ocular localization, metabolism of ω-3-polyunsaturated fatty acids, and functional deficit of the p.H331P variant.
abstract: Bietti's crystalline corneoretinal dystrophy (BCD) is a recessive degenerative eye disease caused by germline mutations in the CYP4V2 gene. More than 80% of mutant alleles consist of three mutations, that is, two splice-site alterations and one missense mutation, c.992C>A, which translates to p.H331P. In the present study, we analyzed the expression of CYP4 family members in human tissues and conducted functional studies with the wild-type and p.H331P enzymes, to elucidate the link between CYP4V2 activity and BCD. Expression analysis of 17 CYP1 to CYP4 genes showed CYP4V2 to be a major cytochrome P450 in ARPE-19 cells (a human cell line spontaneously generated from normal human retinal pigmented epithelium) and the only detectable CYP4 transcript. Immunohistochemical analyses demonstrated that CYP4V2 protein was present in epithelial cells of the retina and cornea and the enzyme was localized to endoplasmic reticulum. Recombinant reconstituted CYP4V2 protein metabolized eicosapentaenoic acid and docosahexaenoic acid (an important constituent of the retina) to their respective ω-hydroxylated products at rates similar to those observed with purified CYP4F2, which is an established hepatic polyunsaturated fatty acid (PUFA) hydroxylase. The disease-associated p.H331P variant was undetectable in Western blot analyses of HepG2 cells stably transduced with lentiviral expression vectors. Finally, overexpression of functional CYP4V2 in HepG2 cells altered lipid homeostasis. We demonstrated that CYP4V2 protein is expressed at high levels in ocular target tissues of BCD, that the enzyme is metabolically active toward PUFAs, and that the functional deficit among patients with BCD who carry the H331P variant is most likely a consequence of the instability of the mutant protein.
authors: Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Washington, USA.
authors: Mariko
authors: M
authors: Nakano
authors: Edward J
authors: EJ
authors: Kelly
authors: Constanze
authors: C
authors: Wiek
authors: Helmut
authors: H
authors: Hanenberg
authors: Allan E
authors: AE
authors: Rettie
mesh_terms: D002460:Cell Line; D003315:Cornea / Q000378:metabolism*; D003317:Corneal Dystrophies, Hereditary / Q000201:enzymology*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D000072470:Cytochrome P450 Family 4; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D015118:Eicosapentaenoic Acid / Q000378:metabolism*; D056945:Hep G2 Cells; D006801:Humans; D050356:Lipid Metabolism; D020125:Mutation, Missense; D009928:Organ Specificity; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012160:Retina / Q000378:metabolism*; D012164:Retinal Diseases / Q000201:enzymology*; D055213:Retinal Pigment Epithelium / Q000166:cytology
chemical_list: D012333:RNA, Messenger; D011994:Recombinant Proteins; D004281:Docosahexaenoic Acids; D003577:Cytochrome P-450 Enzyme System; D015118:Eicosapentaenoic Acid; C505357:CYP4V2 protein, human; D000072470:Cytochrome P450 Family 4