The identification of threonine-95 as the major site of glycosylation in normal human myelin basic protein.
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ABSTRACT:
SUBMITTER: Cruz TF
PROVIDER: S-EPMC1153705 | biostudies-other | 1984 Jun
REPOSITORIES: biostudies-other
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Project description:Compact myelin comprises most of the dry weight of myelin, and its insulative nature is the basis for saltatory conduction of nerve impulses. The major dense line (MDL) is a 3-nm compartment between two cytoplasmic leaflets of stacked myelin membranes, mostly occupied by a myelin basic protein (MBP) phase. MBP is an abundant myelin protein involved in demyelinating diseases, such as multiple sclerosis. The association of MBP with lipid membranes has been studied for decades, but the MBP-driven formation of the MDL remains elusive at the biomolecular level. We employed complementary biophysical methods, including atomic force microscopy, cryo-electron microscopy, and neutron scattering, to investigate the formation of membrane stacks all the way from MBP binding onto a single membrane leaflet to the organisation of a stable MDL. Our results support the formation of an amorphous protein phase of MBP between two membrane bilayers and provide a molecular model for MDL formation during myelination, which is of importance when understanding myelin assembly and demyelinating conditions.
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Project description:An insulating myelin sheath ensures saltatory conduction of mechanosensory A afferents. Myelin damage results in the electrical instability of A fibers and the ability to generate pain in response to light touch/pressure (mechanical allodynia). We have hypothesized and then established that the release of T cell epitopes of myelin basic protein (MBP) enables nociceptive circuitry in myelinated fibers. Thus, mass spectrometry analysis of the rat sciatic nerve proteome followed by bioinformatics examination of the datasets revealed a loss of MBP and activation of T-helper cell signaling in the nerves undergoing chronic constriction injury (CCI). Matrix metalloproteinase-9 (MMP-9) proteolysis resulted in the MBP digest peptides, including the MBP84-104 and MBP68-86 regions, which exhibit prominent immunogenic epitopes. Myelin-forming Schwann cells and paranodal areas accumulated MHCII, MMP-9 and the degraded MBP at the sciatic nerve injury site. Administration of the immunodominant MBP84-104 and MBP68-86 peptides but not of the control peptides in a naïve rat sciatic nerve produced robust mechanical allodynia. Allodynia was accompanied by the T cell infiltration and an increase in MHCII, IL-17A and TNF- levels at the nerve injection site and the segmental ganglia. The pro-nociceptive activity of the synthetic MBP84-104 diminished in athymic nude rats lacking T cells. SB-3CT, an antagonist of MMP-9, inhibited mechanical allodynia, neuroinflammation and spinal sensitization after CCI. Collectively, our novel data implicate, for the first time, MMP-mediated cleavage of MBP and the resulting MBP digest fragments as a major cause of neuropathic pain.
2012-03-03 | GSE34868 | GEO
Project description:An insulating myelin sheath ensures saltatory conduction of mechanosensory A afferents. Myelin damage results in the electrical instability of A fibers and the ability to generate pain in response to light touch/pressure (mechanical allodynia). We have hypothesized and then established that the release of T cell epitopes of myelin basic protein (MBP) enables nociceptive circuitry in myelinated fibers. Thus, mass spectrometry analysis of the rat sciatic nerve proteome followed by bioinformatics examination of the datasets revealed a loss of MBP and activation of T-helper cell signaling in the nerves undergoing chronic constriction injury (CCI). Matrix metalloproteinase-9 (MMP-9) proteolysis resulted in the MBP digest peptides, including the MBP84-104 and MBP68-86 regions, which exhibit prominent immunogenic epitopes. Myelin-forming Schwann cells and paranodal areas accumulated MHCII, MMP-9 and the degraded MBP at the sciatic nerve injury site. Administration of the immunodominant MBP84-104 and MBP68-86 peptides but not of the control peptides in a naïve rat sciatic nerve produced robust mechanical allodynia. Allodynia was accompanied by the T cell infiltration and an increase in MHCII, IL-17A and TNF- levels at the nerve injection site and the segmental ganglia. The pro-nociceptive activity of the synthetic MBP84-104 diminished in athymic nude rats lacking T cells. SB-3CT, an antagonist of MMP-9, inhibited mechanical allodynia, neuroinflammation and spinal sensitization after CCI. Collectively, our novel data implicate, for the first time, MMP-mediated cleavage of MBP and the resulting MBP digest fragments as a major cause of neuropathic pain. Gene extression profiling of total RNAs extracted from rat sciatic nerves, dorsal root ganglion and spinal cords after MBP84-104 peptide injection
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