TAILIEUCHUNG - Báo cáo khoa học: The relative contribution of mannose salvage pathways to glycosylation in PMI-deficient mouse embryonic fibroblast cells

Mannose for mammalian glycan biosynthesis can be imported directly from the medium, derived from glucose or salvaged from endogenous or external glycans. All pathways must generate mannose 6-phosphate, the activated form of mannose. | ễFEBS Journal The relative contribution of mannose salvage pathways to glycosylation in PMI-deficient mouse embryonic fibroblast cells Naonobu Fujita1 Ayako Tamura1 Aya Higashidani1 Takashi Tonozuka1 Hudson H. Freeze2 and Atsushi Nishikawa1 1 Department of Applied BiologicalScience Tokyo University of Agriculture and Technology Japan 2 Tumor Microenvironment Program Burnham Institute for MedicalResearch La Jolla CA USA Keywords congenitaldisorders of glycosylation lipid-linked oligosaccharide mannose N-linked oligosaccharide phosphomannose isomerase Correspondence A. Nishikawa Department of Applied BiologicalScience Tokyo University of Agriculture and Technology 3-5-8 Saiwai-cho Fuchu-shi Tokyo 183-8509 Japan Fax 81 42 367 5705 Tel 81 42 367 5905 E-mail nishikaw@ Received 22 October 2007 revised 6 December 2007 accepted 17 December 2007 doi Mannose for mammalian glycan biosynthesis can be imported directly from the medium derived from glucose or salvaged from endogenous or external glycans. All pathways must generate mannose 6-phosphate the activated form of mannose. Imported or salvaged mannose is directly phosphorylated by hexokinase whereas fructose 6-phosphate from glucose is converted to mannose 6-phosphate by phosphomannose isomerase PMI . Normally PMI provides the majority of mannose for glycan synthesis. To assess the contribution of PMI-independent pathways we used PMI-null fibroblasts to study N-glycosylation of DNase I a highly sensitive indicator protein. In PMI-null cells imported mannose and salvaged mannose make a significant contribution to N-glycosylation. When these cells were grown in mannose-free medium along with the mannosidase inhibitor swainso-nine to block the salvage pathways N-glycosylation of DNase I was almost completely eliminated. Adding 13 pM mannose to the medium completely restored normal glycosylation. Treatment with bafilomycin A1 an inhibitor of lysosomal acidification also markedly

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