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(Na+ + K+)-adenosinetriphosphatase in the brain of Shiverer (Shi/Shi) mice
H J Sheedlo1, G J Siegel, T J Desmond
1Department of Neurology, University of Michigan, Ann Arbor 48109.
Abstract:
The myelin-deficient Shiverer (Shi/Shi) mutant mouse may be a useful model in assessing the dependence of brain (Na+ + K+)-ATPase concentration and composition on myelin membrane formation. Brain microsomal membranes from age-matched control (+/+) and Shiverer (Shi/Shi) mice were fractionated by differential centrifugation and sucrose gradient sedimentation. No reduction in (Na+ + K+)-ATPase specific activity was measured in whole homogenates, high- and low-speed fractions or gradient fractions from brains of Shi/Shi mice as compared to those of +/+ mice. In addition, sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting with antisera specific for mouse brain (Na+ + K+)-ATPase revealed no significant difference in catalytic subunit composition between fractions of +/+ and Shi/Shi brains. The similar results obtained for both +/+ and myelin-deficient Shi/Shi mice suggest that myelin contributes little to total brain (Na+ + K+)-ATPase.
Insights
Myelin-deficient Shiverer mice show no change in brain sodium-potassium ATPase concentration or composition. This suggests myelin formation is not crucial for this important brain enzyme.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- The Shiverer (Shi/Shi) mutant mouse lacks myelin, offering a model to study myelin's role in brain function.
- Brain (Na+ + K+)-ATPase is a critical enzyme for maintaining neuronal ion gradients.
Purpose of the Study:
- To investigate the dependence of brain (Na+ + K+)-ATPase concentration and composition on myelin membrane formation using the Shiverer mouse model.
Main Methods:
- Differential centrifugation and sucrose gradient sedimentation were used to fractionate brain microsomal membranes.
- Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting were employed to analyze enzyme composition.
Main Results:
- No significant reduction in (Na+ + K+)-ATPase specific activity was observed in Shiverer mice compared to controls.
- SDS-PAGE and immunoblotting revealed no significant differences in catalytic subunit composition between Shiverer and control brains.
Conclusions:
- Myelin formation appears to contribute minimally to the total brain (Na+ + K+)-ATPase concentration and composition.
- The Shiverer mouse model is useful for studying enzyme dependence on myelin, but this specific enzyme is largely independent of myelin.