FUNCTIONAL EXPRESSION AND CELLULAR-LOCALIZATION OF A MOUSE EPIDERMAL LIPOXYGENASE

Three distinct murine lipoxygenase genes have been functionally charac terized: 5-lipoxygenase (Chen, X.-S., Naumann, T. A., Kurre, U., Jenki ns, N. A., Copeland, N. G., and Funk, C. D. (1995) J. Biol. Chem. 270, 17993-17999), platelet-type 12-lipoxygenase and leukocyte-type 12-lip oxygenase (Chen, X.-S., Kurre, U., Jenkins, N. A., Copeland, N. G., an d Funk, C. D. (1994) J. Biol. Chem. 269, 13979-13987). Here, we descri be the cloning and functional characterization of a fourth lipoxygenas e gene in mice. Using a polymerase chain reaction-based approach toget her with partial sequence information from a genomic clone, we isolate d a novel lipoxygenase cDNA hom the RNA of 3-6-day old mouse epidermis . The open reading frame predicts a 662-amino acid lipoxygenase that d isplays 60% identity with both murine 12-lipoxygenase isozymes and 40% identity to 5-lipoxygenase; the sequence is identical to a genomic se quence reported recently (van Dijk, K. W., Steketee, K., Havekes, L., Frants, R., and Hofker, M. (1995) Biochim. Biophys. Acta 1259, 4-8). A full-length clone was expressed in human embryonic kidney 293 cells a nd homogenates from disrupted cells produced 12 hydroxyeicosatetraenoi c acid (12-HETE) and minor amounts of 15-HETE from arachidonic acid. C hiral phase analysis indicated that the 12-HETE is exclusively the 12S enantiomer. In situ hybridization revealed highly specific expression of epidermal lipoxygenase in differentiated keratinocytes of the epid ermis and in restricted regions of the root sheath and bulb of hair fo llicles. High expression was also detected in conjunctiva of the eyeli d and in cells of Meibomian and preputial (sebaceous) glands. A 2.4-ki lobase mRNA was detected in mouse epidermis by Northern blot analysis and its abundance was not affected by phorbol ester treatment. The epi dermal lipoxygenase gene (Aloxe) resides on mouse chromosome 11 closel y linked with the two 12-lipoxygenase genes (Alox12p and Alox12l).