title: Recent progress in development of transgenic silkworms overexpressing recombinant human proteins with therapeutic potential in silk glands.
abstract: Since 2000, transgenic silkworms have been developed to produce recombinant proteins with therapeutic potential for future clinical use, including antibody preparations. Lysosomal storage diseases (LSDs) are inherited metabolic disorders caused by mutations of lysosomal enzymes associated with excessive accumulation of natural substrates and neurovisceral symptoms. Over the past few years, enzyme replacement therapy (ERT) with human lysosomal enzymes produced by genetically engineered mammalian cell lines has been used clinically to treat several patients with an LSD involving multi-organ symptoms. ERT is based on the incorporation of recombinant glycoenzymes by their binding to glycan receptors on the surface of target cells and their subsequent delivery to lysosomes. However, ERT has several disadvantages, including difficulty mass producing human enzymes, dangers of pathogen contamination, and high costs. Recently, the current authors have succeeded in producing transgenic silkworms overexpressing human lysosomal enzymes in the silk glands and the authors have purified catalytically active enzymes from the middle silk glands. Silk gland-derived human enzymes carrying high-mannose and pauci-mannose N-glycans were endocytosed by monocytes via the mannose receptor pathway and were then delivered to lysosomes. Conjugates with cell-penetrating peptides were also taken up by cultured fibroblasts derived from patients with enzyme deficiencies to restore intracellular catalytic activity and reduce the excessive accumulation of substrates in patient fibroblasts. Transgenic silkworms overexpressing human lysosomal enzymes in the silk glands could serve as future bioresources that provide safe therapeutic enzymes for the treatment of LSDs. Combining recent developments in transglycosylation technology with microbial endoglycosidases will promote the development of therapeutic glycoproteins as bio-medicines.
authors.affiliation: Department of Medicinal Biotechnology, Institute for Medicinal Research, Graduate School of Pharmaceutical Sciences, Tokushima University.
authors.forename: Kohji
authors.initials: K
authors.lastname: Itoh
authors.forename: Isao
authors.initials: I
authors.lastname: Kobayashi
authors.forename: So-Ichiro
authors.initials: S
authors.lastname: Nishioka
authors.forename: Hideki
authors.initials: H
authors.lastname: Sezutsu
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Machii
authors.forename: Toshiki
authors.initials: T
authors.lastname: Tamura
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D012831:Bombyx / Q000196:embryology / Q000201:enzymology* / Q000235:genetics; D043402:Cathepsin A / Q000096:biosynthesis / Q000627:therapeutic use; D056947:Enzyme Replacement Therapy; D057487:Enzyme Therapy; D004798:Enzymes / Q000096:biosynthesis* / Q000235:genetics; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology; D005822:Genetic Vectors; D006801:Humans; D007814:Larva / Q000201:enzymology / Q000235:genetics; D016464:Lysosomal Storage Diseases / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D008247:Lysosomes / Q000201:enzymology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000627:therapeutic use; D015854:Up-Regulation
chemical_list: D004798:Enzymes; D011994:Recombinant Proteins; C468629:CTSA protein, human; D043402:Cathepsin A