Title:
Recent therapeutic approaches forlysosomal storage diseases
Kohji Itoh, Ph.D.
Department of Medicinal Biotechnology, Institute for Medicinal Research, Graduate School of Pharmaceutical Sciences, The University of Tokushima, 1-78 Sho-machi, Tokushima 770-8505, Japan.
Abstract:
Lysosomal storage diseases (LSDs) are caused by the genetic defects of lysosomal enzymes and related co-factors, associated with excessive accumulation of undegradednatural substrates and heterogeneous clinical manifestations. Several therapeutic approaches for LSDs, including regenerative therapy and gene therapy, have been developed, and especially enzyme replacement therapy (ERT) with recombinant human lysosomal enzyme produced by mammalian cell lines have been clinically applied as the most effective method. The ERT is mainly based on endocytosis of the recombinant lysosomal enzyme through binding of the attached N-glycans carrying terminal mannose 6-phosphate (M6P) residues with cation-independent M6P receptor ( CI-M6PR) expressed on target cell surface. However, the intravenous ERT requires a large amount of recombinant enzymes and high cost, and also has little effect on the neurological manifestations of the patients.
Amethylotrophic yeast, Ogataeaminuta , strain ( Om ), in which the och1 (encoding a -mannosyltransferase) is deleted, and does not express high mannan-type glycans. We established a genetically engineered Om4 strain overexpressing not only the introduced OmMNN4 (encoding a positive regulator of MNN6 gene product, a phosphomannosyltransferase) but also HEXA andHEXB genes, encoding a – and b -subunits of human b -hexosaminidase A (HexA), respectively, to produce a recombinant Om4 HexA ( ab heterodimer), onto which thehuman-like N-glycans carrying high contents of terminalM6P residues after treatment with bacterial a -mannosidase . Sandhoff disease is a HexA deficiency caused by the germ line mutations of HEXB gene, associated with excessive accumulation of GM2 ganglioside (GM2) in brain and neurological manifestations. We administeredthe purified Om4 HexA i ntracerebroventricularly to Sandhoff disease model mouse ( Hexb-/- mouse), and demonstrated the Om4 HexA was taken up by neural cells in brain parenchyma viacell surface CI-M6PR and degraded the substrates including GM2 and terminal GlcNAc-containing oligosaccharides accumulated in lysosomes . We succeeded in improvement of motor dysfunction as well as prolongation of the life span of Hexb-/- mouse in the manner dependent on the M6P content of the recombinant enzyme.These findings suggest the therapeutic potential of intra-cerebrospinal fluid (CSF) ERT and future cell therapy based on the iPS technology.
References:
1. Highly phosphomannosylated enzyme replacement therapy for GM2 gangliosidosis. Tsuji,D. , Akeboshi,H., Matsuoka,K. , Yasuoka,H., Miyasaki,E., Kasahara,Y., Kawashima,I., Chiba ,Y., Jigami,Y., Taki,T., Sakuraba,H., * Itoh,K., Ann.Neurol . 69,691-701 (2010).
2. Therapeutic potential of intracellular replacement of modified human beta-hexosaminidase B for GM2 gangliosidosis. Matsuoka, K., Tamura, T., Tsuji, D., Dohzono, Y., Kitakaze, K., Saito, S., Sakuraba, H. and * Itoh, K. Mol. Ther . 19, 1017-1024 (2011).
3. Introduction of an N-glycan sequon Into HEXA enhances human b -hexosaminidase cellular uptake in a model of Sandhoff disease. Matsuoka, K., Tsuji,D., Aikawa, S., Matsuzawa, F., Sakuraba, H., *Itoh, K. , Mol.Ther .,18,1519-1526 (2010).
