Mutations associated with a congenital form of ichthyosis (NCIE) inactivate the epidermal lipoxygenases 12R-LOX and eLOX3.
Non-bullous congenital ichthyosiform erythroderma (NCIE) is one of the main clinical forms of ichthyosis. Genetic studies indicated that 12R-lipoxygenase (12R-LOX) or epidermal lipoxygenase-3 (eLOX3) was mutated in six families affected by NCIE [F. Jobard, C. Lefevre, A. Karaduman, C. Blanchet-Bardon, S. Emre, J. Weissenbach, M. Ozguc, M. Lathrop, J.F. Prud'homme, J. Fischer, Lipoxygenase-3 (ALOXE3) and 12(R)-lipoxygenase (ALOX12B) are mutated in non-bullous congenital ichthyosiform erythroderma (NCIE) linked to chromosome 17p13.1, Hum. Mol. Genet. 11 (2002) 107-113.], but the impact of these mutations on LOX function has not been defined. To explore this, we overexpressed the wild-type or mutated enzymes in E. coli and COS7 cells and then analyzed the essential catalytic properties. We showed recently that human eLOX3 is a hydroperoxide isomerase (hepoxilin synthase) that converts the product of 12R-LOX, 12R-hydroperoxyeicosatetraenoic acid (12R-HPETE) to a specific epoxyalcohol. Using incubations with [(14)C]-labeled substrates and HPLC analyses, we found that the naturally occurring mutations totally eliminate the lipoxygenase activity of 12R-LOX and the hydroperoxide isomerase activity of eLOX3. We further demonstrate that the 12R-LOX/eLOX3-derived 8R-hydroxy-11R,12R-epoxide is converted by an epoxide hydrolase in COS7 cells and in human keratinocytes to a single isomer of 8,11,12-trihydroxyeicosa-5,9,14-trienoic acid. Taken together, the results support the hypothesis that 12R-LOX, eLOX3, and perhaps an epoxide hydrolase function together in the normal process of skin differentiation, and that the loss of function mutations are the basis of the LOX-dependent form of NCIE.
Yu
Zheyong
Z
Department of Pharmacology, Vanderbilt University School of Medicine, 23rd Ave. at Pierce, Nashville, TN 37232-6602, USA.
Schneider
Claus
C
Boeglin
William E
WE
Brash
Alan R
AR
D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid / Q000378:metabolism; D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000235:genetics* / Q000378:metabolism*; D019556:COS Cells; D002522:Chlorocebus aethiops; D006801:Humans; D017490:Ichthyosis, Lamellar / Q000175:diagnosis / Q000201:enzymology / Q000235:genetics*; D008084:Lipoxygenase / Q000235:genetics* / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation / Q000235:genetics; D011487:Protein Conformation
D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; C095864:lipoxygenase 3; D008084:Lipoxygenase; D001092:Arachidonate 12-Lipoxygenase