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Mutations in demyelinating peripheral neuropathies support molecular model of myelin P0-glycoprotein extracellular
1Laboratory for the Study of Skeletal Disorders, Children's Hospital, Boston, Massachusetts 02115.
Abstract:
Homophilic interactions of the major integral membrane protein of peripheral nerve myelin, P0-glycoprotein, are thought to mediate membrane adhesion and compaction. Molecular modeling of its extracellular domain (P0-ED), based on its resemblance to an immunoglobulin variable domain and on X-ray diffraction measurements of inter-membrane spacings of myelin, has suggested which amino acid sidechains may be involved in the homophilic adhesion. Recently identified point-mutations in the human P0 gene result in amino acid substitutions in P0 protein and correlate with demyelinating motor and sensory neuropathies. The molecular model explains how these changes result in disrupted P0-P0 interactions; indicates how compensatory changes in amino acids, as occur in P0-ED of other species, preserve normal homophilic interactions; and predicts what other residue substitutions might underlie additional cases of demyelinating neuropathies.
Insights
Homophilic interactions of P0-glycoprotein are crucial for myelin compaction. Molecular modeling explains how mutations cause neuropathies and predicts others, aiding understanding of demyelinating diseases.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- P0-glycoprotein is the major integral membrane protein in peripheral nerve myelin.
- Homophilic interactions of P0-glycoprotein are essential for myelin adhesion and compaction.
- Mutations in the P0 gene are linked to demyelinating neuropathies.
Purpose of the Study:
- To investigate the molecular mechanisms of P0-glycoprotein homophilic interactions.
- To understand how P0 gene mutations lead to demyelinating neuropathies.
- To predict potential new mutations causing demyelinating neuropathies.
Main Methods:
- Molecular modeling of the P0-glycoprotein extracellular domain (P0-ED).
- Analysis of X-ray diffraction data of myelin inter-membrane spacing.
- Correlation of identified human P0 gene point-mutations with disease phenotypes.
Main Results:
- The molecular model identified specific amino acid sidechains involved in P0-P0 homophilic adhesion.
- The model explains how disease-associated mutations disrupt P0-P0 interactions.
- The model accounts for compensatory mutations in P0-ED from other species that maintain normal interactions.
Conclusions:
- Molecular modeling provides a framework for understanding P0-glycoprotein function in myelin.
- The study elucidates the molecular basis of P0-related neuropathies.
- This research predicts novel P0 residue substitutions associated with demyelinating neuropathies.