Towards abolition of immunogenic structures in insect cells: characterisation of a honey-bee (Apis mellifera) multi-gene family reveals both an allergy-related core {alpha}1,3-fucosyltransferase and the first insect Lewis-histo-blood group-related antigen-synthesising enzyme
Résumé
Glycoproteins from Apis mellifera, such as phospholipase A 2} and hyaluronidase are well known major bee venom allergens. They carry N-linked oligosaccharide structures with two types of {alpha}1,3-fucosylation: the modification by {alpha}1,3-fucose of the innermost core GlcNAc, which constitutes an epitope recognised by IgE from some bee venom allergic patients, and a antennal Lewis-like GalNAc{beta}1,4(Fuc{alpha}1,3)GlcNAc moiety. We now report the cloning and expression of two cDNAs encoding the relevant active {alpha}1,3-fucosyltransferases. The first sequence, closest to Drosophila melanogaster FucTA, was found to be a core {alpha}1,3-fucosyltransferase (EC 2.4.1.214), as judged by several enzyme and biochemical assays. The second cDNA encoded an enzyme, most related to Drosophila FucTC, was shown to be capable of generating the Le x} epitope in vitro and is the first Lewis-type {alpha}1,3-fucosyltransferase (EC 2.4.1.152) to be described in insects. The transcription levels these two genes in various tissues were examined: FucTA was found to be predominantly expressed in the brain tissue and venom glands, whereas FucTC transcripts were detected at highest levels in venom and hypopharyngeal glands. Very low expression of a third homologue of unknown function, FucTB, was also observed in various tissues. The characterisation of these honeybee gene products not only accounts for the observed {alpha}1,3-fucosylation of bee venom glycoproteins, but is expected to aid the identification and subsequent down-regulation of the fucosyltransferases in insect cell lines of biotechnological importance.
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