Ablation of mouse phosphomannose isomerase (Mpi) causes mannose 6-phosphate accumulation, toxicity, and embryonic lethality
(2006) In The Journal of biological chemistry 281(9). p.5916-5927- Abstract
MPI encodes phosphomannose isomerase, which interconverts fructose 6-phosphate and mannose 6-phosphate (Man-6-P), used for glycoconjugate biosynthesis. MPI mutations in humans impair protein glycosylation causing congenital disorder of glycosylation Ib (CDG-Ib), but oral mannose supplements normalize glycosylation. To establish a mannose-responsive mouse model for CDG-Ib, we ablated Mpi and provided dams with mannose to rescue the anticipated defective glycosylation. Surprisingly, although glycosylation was normal, Mpi(-/-) embryos died around E11.5. Mannose supplementation even hastened their death, suggesting that man-nose was toxic. Mpi(-/-) embryos showed growth retardation and placental hyperplasia. More than 90% of Mpi(-/-)... (More)
MPI encodes phosphomannose isomerase, which interconverts fructose 6-phosphate and mannose 6-phosphate (Man-6-P), used for glycoconjugate biosynthesis. MPI mutations in humans impair protein glycosylation causing congenital disorder of glycosylation Ib (CDG-Ib), but oral mannose supplements normalize glycosylation. To establish a mannose-responsive mouse model for CDG-Ib, we ablated Mpi and provided dams with mannose to rescue the anticipated defective glycosylation. Surprisingly, although glycosylation was normal, Mpi(-/-) embryos died around E11.5. Mannose supplementation even hastened their death, suggesting that man-nose was toxic. Mpi(-/-) embryos showed growth retardation and placental hyperplasia. More than 90% of Mpi(-/-) embryos failed to form yolk sac vasculature, and 35% failed chorioallantoic fusion. We generated primary embryonic fibroblasts to investigate the mechanisms leading to embryonic lethality and found that mannose caused a concentration- and time-dependent accumulation of Man 6-P in Mpi(-/-) fibroblasts. In parallel, ATP decreased by more than 70% after 24 h compared with Mpi(+/+) controls. In cell lysates, Man-6-P inhibited hexokinase (70%), phosphoglucose isomerase (65%), and glucose-6-phosphate dehydrogenase (85%), but not phosphofructokinase. Incubating intact Mpi(-/-) fibroblasts with 2-[(3)H]deoxyglucose confirmed mannose-dependent hexokinase inhibition. Our results in vitro suggest that mannose toxicity in Mpi(-/-) embryos is caused by Man-6-P accumulation, which inhibits glucose metabolism and depletes intracellular ATP. This was confirmed in E10.5 Mpi(-/-) embryos where Man-6-P increased more than 10 times, and ATP decreased by 50% compared with Mpi(+/+) littermates. Because Mpi ablation is embryonic lethal, a murine CDG-Ib model will require hypomorphic Mpi alleles.
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- author
- DeRossi, Charles ; Bode, Lars ; Eklund, Erik A LU ; Zhang, Fangrong ; Davis, Joseph A ; Westphal, Vibeke ; Wang, Ling ; Borowsky, Alexander D and Freeze, Hudson H
- publishing date
- 2006
- type
- Contribution to journal
- publication status
- published
- keywords
- Adenosine Triphosphate/metabolism, Animals, Carbohydrate Metabolism, Inborn Errors, Cells, Cultured, Embryo Loss, Embryo, Mammalian/anatomy & histology, Female, Fibroblasts/cytology, Gene Targeting, Genotype, Gestational Age, Hexokinase/metabolism, Humans, Male, Mannose/administration & dosage, Mannose-6-Phosphate Isomerase/deficiency, Mannosephosphates/metabolism, Mice, Mice, Knockout, Polysaccharides/biosynthesis, Pregnancy
- in
- The Journal of biological chemistry
- volume
- 281
- issue
- 9
- pages
- 5916 - 5927
- publisher
- American Society for Biochemistry and Molecular Biology
- external identifiers
-
- scopus:33646832614
- pmid:16339137
- ISSN
- 0021-9258
- DOI
- 10.1074/jbc.M511982200
- language
- English
- LU publication?
- no
- id
- 512cad78-e8e6-4a5a-a705-f2385a6b34e0
- date added to LUP
- 2021-10-12 00:04:24
- date last changed
- 2024-04-06 10:58:28
@article{512cad78-e8e6-4a5a-a705-f2385a6b34e0,
abstract = {{<p>MPI encodes phosphomannose isomerase, which interconverts fructose 6-phosphate and mannose 6-phosphate (Man-6-P), used for glycoconjugate biosynthesis. MPI mutations in humans impair protein glycosylation causing congenital disorder of glycosylation Ib (CDG-Ib), but oral mannose supplements normalize glycosylation. To establish a mannose-responsive mouse model for CDG-Ib, we ablated Mpi and provided dams with mannose to rescue the anticipated defective glycosylation. Surprisingly, although glycosylation was normal, Mpi(-/-) embryos died around E11.5. Mannose supplementation even hastened their death, suggesting that man-nose was toxic. Mpi(-/-) embryos showed growth retardation and placental hyperplasia. More than 90% of Mpi(-/-) embryos failed to form yolk sac vasculature, and 35% failed chorioallantoic fusion. We generated primary embryonic fibroblasts to investigate the mechanisms leading to embryonic lethality and found that mannose caused a concentration- and time-dependent accumulation of Man 6-P in Mpi(-/-) fibroblasts. In parallel, ATP decreased by more than 70% after 24 h compared with Mpi(+/+) controls. In cell lysates, Man-6-P inhibited hexokinase (70%), phosphoglucose isomerase (65%), and glucose-6-phosphate dehydrogenase (85%), but not phosphofructokinase. Incubating intact Mpi(-/-) fibroblasts with 2-[(3)H]deoxyglucose confirmed mannose-dependent hexokinase inhibition. Our results in vitro suggest that mannose toxicity in Mpi(-/-) embryos is caused by Man-6-P accumulation, which inhibits glucose metabolism and depletes intracellular ATP. This was confirmed in E10.5 Mpi(-/-) embryos where Man-6-P increased more than 10 times, and ATP decreased by 50% compared with Mpi(+/+) littermates. Because Mpi ablation is embryonic lethal, a murine CDG-Ib model will require hypomorphic Mpi alleles.</p>}},
author = {{DeRossi, Charles and Bode, Lars and Eklund, Erik A and Zhang, Fangrong and Davis, Joseph A and Westphal, Vibeke and Wang, Ling and Borowsky, Alexander D and Freeze, Hudson H}},
issn = {{0021-9258}},
keywords = {{Adenosine Triphosphate/metabolism; Animals; Carbohydrate Metabolism, Inborn Errors; Cells, Cultured; Embryo Loss; Embryo, Mammalian/anatomy & histology; Female; Fibroblasts/cytology; Gene Targeting; Genotype; Gestational Age; Hexokinase/metabolism; Humans; Male; Mannose/administration & dosage; Mannose-6-Phosphate Isomerase/deficiency; Mannosephosphates/metabolism; Mice; Mice, Knockout; Polysaccharides/biosynthesis; Pregnancy}},
language = {{eng}},
number = {{9}},
pages = {{5916--5927}},
publisher = {{American Society for Biochemistry and Molecular Biology}},
series = {{The Journal of biological chemistry}},
title = {{Ablation of mouse phosphomannose isomerase (Mpi) causes mannose 6-phosphate accumulation, toxicity, and embryonic lethality}},
url = {{http://dx.doi.org/10.1074/jbc.M511982200}},
doi = {{10.1074/jbc.M511982200}},
volume = {{281}},
year = {{2006}},
}