Inhibition of calcium uptake via the sarco/endoplasmic reticulum Ca2+-ATPase in a mouse model of Sandhoff disease and prevention by treatment with N-butyldeoxynojirimycin.
Gangliosides are found at high levels in neuronal tissues where they play a variety of important functions. In the gangliosidoses, gangliosides accumulate because of defective activity of the lysosomal proteins responsible for their degradation, usually resulting in a rapidly progressive neurodegenerative disease. However, the molecular mechanism(s) leading from ganglioside accumulation to neurodegeneration is not known. We now examine the effect of ganglioside GM2 accumulation in a mouse model of Sandhoff disease (one of the GM2 gangliosidoses), the Hexb-/- mouse. Microsomes from Hexb-/- mouse brain showed a significant reduction in the rate of Ca2+-uptake via the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), which was prevented by feeding Hexb-/- mice with N-butyldeoxynojirimycin (NB-DNJ), an inhibitor of glycolipid synthesis that reduces GM2 storage. Changes in SERCA activity were not due to transcriptional regulation but rather because of a decrease in Vmax. Moreover, exogenously added GM2 had a similar effect on SERCA activity. The functional significance of these findings was established by the enhanced sensitivity of neurons cultured from embryonic Hexb-/- mice to cell death induced by thapsigargin, a specific SERCA inhibitor, and by the enhanced sensitivity of Hexb-/- microsomes to calcium-induced calcium release. This study suggests a mechanistic link among GM2 accumulation, reduced SERCA activity, and neuronal cell death, which may be of significance for delineating the neuropathophysiology of Sandhoff disease.
Pelled
Dori
D
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
Lloyd-Evans
Emyr
E
Riebeling
Christian
C
Jeyakumar
Mylvaganam
M
Platt
Frances M
FM
Futerman
Anthony H
AH
D017485:1-Deoxynojirimycin / Q000031:analogs & derivatives / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D016923:Cell Death; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005678:G(M2) Ganglioside / Q000378:metabolism; D005732:Gangliosides / Q000378:metabolism; D005838:Genotype; D006017:Glycolipids / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D007700:Kinetics; D050356:Lipid Metabolism; D051379:Mice; D008822:Mice, Transgenic; D008861:Microsomes / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012497:Sandhoff Disease / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013053:Spectrophotometry; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors
D004791:Enzyme Inhibitors; D005732:Gangliosides; D006017:Glycolipids; D017485:1-Deoxynojirimycin; D005678:G(M2) Ganglioside; D019284:Thapsigargin; D000255:Adenosine Triphosphate; C059896:miglustat; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium