Degradation Of Myelin Basic Protein Research Articles

Fructus mume alleviates chronic cerebral hypoperfusion-induced white matter and hippocampal damage via inhibition of inflammation and downregulation of TLR4 and p38 MAPK signaling.

BackgroundFructus mume (F. mume) has been used as a traditional medicine for many years in Asian countries. The present study was designed to determine the effect of a 70% ethanol extract of F. mume on white matter and hippocampal damage induced by chronic cerebral hypoperfusion.MethodsPermanent bilateral common carotid artery occlusion (BCCAo) was performed on male Wistar rats to induce chronic cerebral hypoperfusion. Daily oral administration of F. mume (200 mg/kg) was initiated 21 days after BCCAo and continued for 42 days. The experimental groups in this study were divided into three groups: a sham-operated group, a BCCAo group, and a BCCAo group that was administered with the F. mume extract. The activation of glial cells, including microglia and astrocytes, and the levels of myelin basic protein (MBP), inflammatory mediators, Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), and p38 mitogen-activated protein kinase (MAPK) phosphorylation were measured in brains from rats subjected to chronic BCCAo.ResultsOur results revealed that F. mume alleviates the reduction in MBP expression caused by chronic BCCAo in the white matter and the hippocampus and significantly attenuates microglial and astrocytic activation induced by chronic BCCAo in the optic tract of white matter. In addition, F. mume treatment reduced the increased expression of cyclooxygenase-2 (COX-2), interleukin-1β (IL-1β) and interleukin-6 (IL-6), as well as the activation of TLR4/MyD88 and p38 MAPK signaling, in the hippocampus of rats subjected to chronic BCCAo.ConclusionTaken together, our findings demonstrate that brain injury induced by chronic BCCAo is ameliorated by the anti-inflammatory effects of F. mume via inhibition of MBP degradation, microglial and astrocytic activation, increased inflammatory mediator expression, and activated intracellular signalings, including TLR4 and p38 MAPK, implying that F. mume is potentially an effective therapeutics for the treatment of vascular dementia.Electronic supplementary materialThe online version of this article (doi:10.1186/s12906-015-0652-1) contains supplementary material, which is available to authorized users.

Allopurinol reduces severity of delayed neurologic sequelae in experimental carbon monoxide toxicity in rats

Approximately half of those who survive severe carbon monoxide (CO) poisoning develop delayed neurologic sequelae. Growing evidence supports the crucial role of free radicals in delayed brain injury associated with CO toxicity. Xanthine oxidase (XO) has been reported to play a pivotal role in the generation of reactive oxygen species (ROS) in CO poisoning. A recent report indicates that allopurinol both attenuated oxidative stress and possessed anti-inflammatory properties in an animal model of acute liver failure. In this study, we aimed to explore the potential of allopurinol to reduce the severity of delayed neurologic sequelae. The rats were first exposed to 1000ppm CO for 40min and then to 3000ppm CO for another 20min. Following CO poisoning, the rats were injected with allopurinol (50mg/kg, i.p.) six times. Results showed that allopurinol significantly reduced neuronal death and suppressed expression of pro-inflammatory factors, including tumor necrosis factor-α, intercellular adhesion molecule-1, ionized calcium-binding adapter molecule 1, and degraded myelin basic protein. Furthermore, behavioral studies revealed an improved performance in the Morris water maze test. Our findings indicated that allopurinol may have protective effects against delayed neurologic sequelae caused by CO toxicity.

Myelin basic protein associates with AβPP, Aβ1-42, and amyloid plaques in cortex of Alzheimer's disease brain.

The goal of this study was to show that myelin and axons in cortical gray matter are damaged in Alzheimer's disease (AD) brain. Superior temporal gyrus gray matter of AD patients (9 male, 14 female) was compared to cognitively normal controls (8 male, 7 female). Myelin basic protein (MBP) and a degraded myelin basic protein complex (dMBP) were quantified by Western blot. Brain sections were immunostained for MBP, dMBP, axonal neurofilament protein (NF), autophagy marker microtubule-associated proteins 1A/B light chain 3B precursor (LC3B), amyloid-β protein precursor (AβPP), and amyloid markers amyloid β1-42 (Aβ1-42) and FSB. Co-immunoprecipitation and mass spectroscopy evaluated interaction of AβPP/Aβ1-42 with MBP/dMBP. Evidence of axonal injury in AD cortex included appearance of AβPP in NF stained axons, and NF at margins of amyloid plaques. Evidence of myelin injury in AD cortex included (1) increased dMBP in AD gray matter compared to control (p < 0.001); (2) dMBP in AD neurons; and (3) increased LC3B that co-localized with MBP. Evidence of interaction of AβPP/Aβ1-42 with myelin or axonal components included (1) greater binding of dMBP with AβPP in AD brain; (2) MBP at the margins of amyloid plaques; (3) dMBP co-localized with Aβ1-42 in the core of amyloid plaques in AD brains; and (4) interactions between Aβ1-42 and MBP/dMBP by co-immunoprecipitation and mass spectrometry. We conclude that damaged axons may be a source of AβPP. dMBP, MBP, and NF associate with amyloid plaques and dMBP associates with AβPP and Aβ1-42. These molecules could be involved in formation of amyloid plaques.

Ubiquitin-independent proteosomal degradation of myelin basic protein contributes to development of neurodegenerative autoimmunity.

Recent findings indicate that the ubiquitin–proteasome system is involved in the pathogenesis of cancer as well as autoimmune and several neurodegenerative diseases, and is thus a target for novel therapeutics. One disease that is related to aberrant protein degradation is multiple sclerosis, an autoimmune disorder involving the processing and presentation of myelin autoantigens that leads to the destruction of axons. Here, we show that brain-derived proteasomes from SJL mice with experimental autoimmune encephalomyelitis (EAE) in an ubiquitin-independent manner generate significantly increased amounts of myelin basic protein peptides that induces cytotoxic lymphocytes to target mature oligodendrocytes ex vivo. Ten times enhanced release of immunogenic peptides by cerebral proteasomes from EAE-SJL mice is caused by a dramatic shift in the balance between constitutive and β1ihigh immunoproteasomes in the CNS of SJL mice with EAE. We found that during EAE, β1i is increased in resident CNS cells, whereas β5i is imported by infiltrating lymphocytes through the blood–brain barrier. Peptidyl epoxyketone specifically inhibits brain-derived β1ihigh immunoproteasomes in vitro (kobs/[I] = 240 M−1s−1), and at a dose of 0.5 mg/kg, it ameliorates ongoing EAE in vivo. Therefore, our findings provide novel insights into myelin metabolism in pathophysiologic conditions and reveal that the β1i subunit of the immunoproteasome is a potential target to treat autoimmune neurologic diseases.—Belogurov Jr., A., Kuzina, E., Kudriaeva, A., Kononikhin, A., Kovalchuk, S., Surina, Y., Smirnov, I., Lomakin, Y., Bacheva, A., Stepanov, A., Karpova, Y., Lyupina, Y., Kharybin, O., Melamed, D., Ponomarenko, N., Sharova, N., Nikolaev, E., Gabibov, A. Ubiquitin-independent proteosomal degradation of myelin basic protein contributes to development of neurodegenerative autoimmunity.

Alcohol binge drinking during adolescence or dependence during adulthood reduces prefrontal myelin in male rats.

Teen binge drinking is associated with low frontal white matter integrity and increased risk of alcoholism in adulthood. This neuropathology may result from alcohol exposure or reflect a pre-existing condition in people prone to addiction. Here we used rodent models with documented clinical relevance to adolescent binge drinking and alcoholism in humans to test whether alcohol damages myelinated axons of the prefrontal cortex. In Experiment 1, outbred male Wistar rats self-administered sweetened alcohol or sweetened water intermittently for 2 weeks during early adolescence. In adulthood, drinking behavior was tested under nondependent conditions or after dependence induced by 1 month of alcohol vapor intoxication/withdrawal cycles, and prefrontal myelin was examined 1 month into abstinence. Adolescent binge drinking or adult dependence induction reduced the size of the anterior branches of the corpus callosum, i.e., forceps minor (CCFM), and this neuropathology correlated with higher relapse-like drinking in adulthood. Degraded myelin basic protein in the gray matter medial to the CCFM of binge rats indicated myelin was damaged on axons in the mPFC. In follow-up studies we found that binge drinking reduced myelin density in the mPFC in adolescent rats (Experiment 2) and heavier drinking predicted worse performance on the T-maze working memory task in adulthood (Experiment 3). These findings establish a causal role of voluntary alcohol on myelin and give insight into specific prefrontal axons that are both sensitive to alcohol and could contribute to the behavioral and cognitive impairments associated with early onset drinking and alcoholism.

Glatiramer acetate and nanny proteins restrict access of the multiple sclerosis autoantigen myelin basic protein to the 26S proteasome.

We recently showed that myelin basic protein (MBP) is hydrolyzed by 26S proteasome without ubiquitination. The previously suggested concept of charge-mediated interaction between MBP and the proteasome led us to attempt to compensate or mimic its positive charge to inhibit proteasomal degradation. We demonstrated that negatively charged actin and calmodulin (CaM), as well as basic histone H1.3, inhibit MBP hydrolysis by competing with the proteasome and MBP, respectively, for binding their counterpart. Interestingly, glatiramer acetate (GA), which is used to treat multiple sclerosis (MS) and is structurally similar to MBP, inhibits intracellular and in vitro proteasome-mediated MBP degradation. Therefore, the data reported in this study may be important for myelin biogenesis in both the normal state and pathophysiological conditions.

Topical application of brain derived neurotrophic factor attenuates spinal cord trauma induced edema and myelin damage

Influence of brain derived neurotrophic factor on spinal cord trauma induced edema formation and myelin damage was examined using immunohistochemical and ultrastructural investigations. A focal trauma to the rat spinal cord (right dorsal horn lesion, T10–/INS;11) induces degradation of myelin basic protein (MBP) immunoreactivity in both spinal cord gray and white matter at 5h. This decrease in MBP immunoreactivity was most pronounced in the vicinity of the injured spinal cord. A general expansion of the cord and swelling of gray and white matter is clearly evident.

SC1/Hevin Identifies Early White Matter Injury After Ischemia and Intracerebral Hemorrhage in Young and Aged Rats

The progression of white matter damage after ischemic and hemorrhagic strokes can exacerbate the initial injury, but little is known about the processes involved. We show that the antiadhesive matricellular glycoprotein SC1 is a novel early marker of white matter damage in 3 models of acute injury in the rat striatum: transient focal ischemia, intracerebral hemorrhage, and a needle penetration wound. SC1 was restricted to the damaged portions of axon bundles that bordered stroke lesions in young-adult and aged rats. SC1 peaked at 1 and 3 days after intracerebral hemorrhage and at 7 days after ischemia. The SC1-positive bundles usually expressed degraded myelin basic protein and amyloid precursor protein, a marker of axonal injury. At the hematoma edge, SC1 was seen in a few axon bundles that retained myelin basic protein staining. In these bundles, punctate SC1 staining filled individual axons, extended beyond a core of pan-axonal neurofilament and NF200 and was inside or overlapped with myelin basic protein staining when it was present. Aged rats had less SC1 (and amyloid precursor protein) after both types of stroke, suggesting a reduced axonal response. SC1 also labeled amyloid precursor protein-positive axon bundles along the needle penetration tract of saline-injected rats; thus, SC1 appears to characterize damaged striatal white matter damage after multiple types of injury.

Hydrogen-rich saline reduces delayed neurologic sequelae in experimental carbon monoxide toxicity

We investigated the feasibility and efficacy of hydrogen-rich saline therapy on delayed neurologic sequelae in a rat model of severe acute carbon monoxide (CO) poisoning. Controlled animal study. University research laboratory for Diving Medicine. Sprague-Dawley rats weighing 250 ± 20 g. The rats were exposed to 1000 ppm CO in air for 40 min and then to 3000 ppm for another 20 min until they lost consciousness. Rats were intraperitoneal injected with hydrogen-rich saline or normal saline (10 mL/kg) for six times after resuscitation at 0, 12, 24, 36, 48, and 60 hrs, respectively. The rats without CO poisoning were used as normal controls. Brain tissue inflammation, cell death, and cognitive dysfunction were observed at one week after CO poisoning. Hydrogen-rich saline treatment significantly reduced the level of degraded myelin basic protein, decreased the expression of ionized calcium-binding adapter molecule 1, Iba1, a microglial marker, reduced DNA oxidation, and suppressed proinflammatory cytokine interleukin-1β, interleukin-6, and tumor necrosis factor-α in the cortex and hippocampal tissues when compared with those in normal saline-treated rats. These histologic and biological improvements were accompanied with an improvement in the Morris water maze test. This observation demonstrated that hydrogen-rich saline peritoneal injection improves histologic and functional assessment in a rat model of CO encephalopathy. Hydrogen saline has potentials as a novel and alternative therapy for severely CO-poisoned patients with delayed neurologic sequelae. The therapeutic effects of hydrogen-rich saline may be related to antioxidant and anti-inflammatory actions.

Matrix Metalloproteinases Are Associated With Increased Blood–Brain Barrier Opening in Vascular Cognitive Impairment

Subcortical ischemic vascular disease (SIVD) is a major form of vascular cognitive impairment (VCI) due to small vessel disease. Matrix metalloproteinases (MMPs) are neutral proteases that disrupt the blood-brain barrier and degrade myelin basic protein under conditions of neuroinflammation. Brain tissues and cerebrospinal fluid (CSF) of patients with VCI have increased levels of MMPs. We hypothesized that patients with SIVD have increased MMPs in the CSF, which are associated with increased CSF albumin. We studied 60 patients with suspected VCI. Twenty-five were classified as SIVD, whereas other groups included mixed Alzheimer disease and VCI, multiple strokes, and leukoaraiosis when white matter lesions were present and the diagnosis of VCI was uncertain. MMP-2 and MMP-9 in CSF and plasma were measured by gel zymography and indexed to CSF and plasma albumin. MMP-3 activity was measured by fluorescent assay. We found reduced MMP-2 index (P<0.001) in the CSF for the full group of patients (SIVD, multiple strokes, mixed Alzheimer disease and VCI, and leukoaraiosis) compared with control subjects, whose CSF was obtained during spinal anesthesia. MMP-3 activity was increased in VCI compared with control subjects (P<0.01). In SIVD, MMP-2 index showed a negative correlation with albumin index, which was absent with the MMP-9 index. Combining MMP-2 index and MMP-3 activity separated the patients with SIVD from the control subjects with high specificity (P<0.0005). Our results support the hypothesis that MMPs are associated with increased CSF albumin and suggest that they may contribute to the pathophysiology of SIVD.

Acrolein induces myelin damage in mammalian spinal cord

Myelin damage can lead to the loss of axonal conduction and paralysis in multiple sclerosis and spinal cord injury. Here, we show that acrolein, a lipid peroxidation product, can cause significant myelin damage in isolated guinea pig spinal cord segments. Acrolein-mediated myelin damage is particularly conspicuous in the paranodal region in both a calcium dependent (nodal lengthening) and a calcium-independent manner (paranodal myelin splitting). In addition, paranodal protein complexes can dissociate with acrolein incubation. Degraded myelin basic protein is also detected at the paranodal region. Acrolein-induced exposure and redistribution of paranodal potassium channels and the resulting axonal conduction failure can be partially reversed by 4-AP, a potassium channel blocker. From this data, it is clear that acrolein is capable of inflicting myelin damage as well as axonal degeneration, and may represent an important factor in the pathogenesis in multiple sclerosis and spinal cord injury.

Functional degradation of myelin basic protein. The proteomic approach

Proteolytic degradation of autoantigens is of prime importance in current biochemistry and immunology. The most fundamental issue in this field is the functional role of peptides produced when the specificity of hydrolysis changes during the shift from health to disease and from normal state to pathology. The identification of specific peptide fragments in many cases proposes the diagnostic and prognostic criterion in the pathology progression. The aim of this work is comparative study of the degradation peculiarities of one of the main neuroantigen, myelin basic protein by proteases, activated during progress of pathological demyelinating process, and by proteasome of different origin. The comparison of specificity of different studied biocatalysts gives reason to discuss the critical change in the set of myelin basic protein fragments capable to be presented by major histocompatibility complex class I during neurodegeneration, which can promote the progress of autoimmune pathological process.

Transient degradation of myelin basic protein in the rat hippocampus following acute carbon monoxide poisoning

The neurotoxicity of carbon monoxide (CO) poisoning is a significant clinical problem, but its mechanisms remain unclear. Previous studies of CO-exposed rats showed spatial memory disturbances and degradation of myelin basic protein (MBP) in the brain; however, regional localization of the degradation was not analyzed. In the present study, we histologically determined the foci of CO effects in the hippocampus. Wistar rats were exposed to CO for 60 min (1000 ppm for 40 min + 3000 ppm for 20 min) and returned into room air. For histological evaluation, the animals were sacrificed 90 min, 1, 7 and 14 days after CO exposure and the brain tissue was analyzed with hematoxylin–eosin (HE), Nissl and Gallyas myelin staining as well as immunohistochemistry for MBP and phosphorylated or nonphosphorylated neurofilament. No histological changes were observed on HE, Nissl or Gallyas staining. In contrast, we detected MBP reduction at 90 min after CO exposure in the dentate gyrus and CA3, and the recovery of MBP was observed after 14 days. The immunoreactivity of neurofilament also changed after CO exposure. Nevertheless, water maze test showed no significant effects of CO exposure on spatial memory. Our findings demonstrate that CO poisoning causes transient degradation of MBP and axonal injury in the hippocampus even though the animals showed no neurological disturbances.

Quantification of myelin loss in frontal lobe white matter in vascular dementia, Alzheimer’s disease, and dementia with Lewy bodies

The aim of this study was to characterize myelin loss as one of the features of white matter abnormalities across three common dementing disorders. We evaluated post-mortem brain tissue from frontal and temporal lobes from 20 vascular dementia (VaD), 19 Alzheimer’s disease (AD) and 31 dementia with Lewy bodies (DLB) cases and 12 comparable age controls. Images of sections stained with conventional luxol fast blue were analysed to estimate myelin attenuation by optical density. Serial adjacent sections were then immunostained for degraded myelin basic protein (dMBP) and the mean percentage area containing dMBP (%dMBP) was determined as an indicator of myelin degeneration. We further assessed the relationship between dMBP and glutathione S-transferase (a marker of mature oligodendrocytes) immunoreactivities. Pathological diagnosis significantly affected the frontal but not temporal lobe myelin attenuation: myelin density was most reduced in VaD compared to AD and DLB, which still significantly exhibited lower myelin density compared to ageing controls. Consistent with this, the degree of myelin loss was correlated with greater %dMBP, with the highest %dMBP in VaD compared to the other groups. The %dMBP was inversely correlated with the mean size of oligodendrocytes in VaD, whereas it was positively correlated with their density in AD. A two-tier regression model analysis confirmed that the type of disorder (VaD or AD) determines the relationship between %dMBP and the size or density of oligodendrocytes across the cases. Our findings, attested by the use of three markers, suggest that myelin loss may evolve in parallel with shrunken oligodendrocytes in VaD but their increased density in AD, highlighting partially different mechanisms are associated with myelin degeneration, which could originate from hypoxic–ischaemic damage to oligodendrocytes in VaD whereas secondary to axonal degeneration in AD.

Analysis of Myelin Basic Protein Fragmentation by Proteasome

The proteasome is a high molecular protein complex whose purpose is specific protein degradation in eukaryotic cells. One of the proteasome functions is to produce peptides, which will then be presented on the outer cell membrane using main histocompatibility complex (MHC) molecules of the first or second class. There are definite reasons to believe that proteasome directly takes part in the specific degradation of myelin basic protein (MBP), which make up to 30% of all proteins in the myelin sheath of neuronal axons. The details of the proteasomal degradation of MBP are still unclear. In this work, the features of specific MBP degradation by proteasome were studied.It was demonstrated that MBP (non-ubiquitinated) is a good substrate for 20S and for the 26S proteasome. This is the first work on detecting the sites of MBP proteolysis by proteasome from brains of SJL/J/J and Balb/C mice's lines. Substantial differences in the degradation pattern of this neuroantigen were found, which could indicate the better presentation MBP parts on MHC molecules in the case of mice predisposed to the development of experimental autoimmune encephalomyelitis.

Neuropathological Correlates of Temporal Pole White Matter Hyperintensities in CADASIL

White matter (WM) hyperintensities on MRI or leukoaraiosis is characteristic of stroke syndromes. Increased MRI signals in the anterior temporal pole are suggested to be diagnostic for cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), with 90% sensitivity and 100% specificity. The structural correlates of these specific WM hyperintensities seen on T2-weighted and FLAIR sequences in the temporal pole of CADASIL are unclear. We assessed pathological changes in postmortem tissue from the temporal pole to reveal the cause of CADASIL-specific WM hyperintensities. A combination of tinctorial and immunostaining approaches and in vitro imaging methods were used to quantify the extent of perivascular space (PVS), arteriosclerosis determined as the sclerotic index, WM myelination as the myelin index, and damage within the WM as accumulated degraded myelin basic protein in samples of the anterior temporal pole from 9 CADASIL and 8 sporadic subcortical ischemic vascular dementia cases, and 5 similarly aged (young) and 5 older controls. Luxol fast blue-stained serial sections from a CADASIL case were also used to reconstruct the temporal pole, which was then compared to the MR images. Luxol fast blue sections used to reconstruct the temporal pole revealed an abundance of enlarged PVS in the WM that topographically appeared as indistinct opaque regions. The mean and total areas of the PVS per WM area (%PVS) were significantly greater in CADASIL compared to the controls. The myelin index was severely reduced in CADASIL in relation to the subcortical ischemic vascular dementia and control sample that was consistent with increased immunoreactivity of degraded myelin basic protein, indicating myelin degeneration. Cerebral microvessels associated with the PVS exhibited a 4.5-fold greater number of basophilic (hyalinized) vessels and a 57% increase in the sclerotic index values in CADASIL subjects compared to young controls. A significant correlation between the quantity of hyalinized vessels and sclerotic index values was also apparent (P<0.05). Our findings suggest that MRI hyperintensities in the temporal pole of CADASIL patients are explained by enlarged PVS and degeneration of myelin accompanied by lack of drainage of the interstitial fluid rather than lacunar infarcts. Consistent with the lack of MR hypersignals in the temporal pole of older subcortical ischemic vascular dementia subjects, our observations imply greater progression of pathological changes in CADASIL patients.

Site-specific degradation of myelin basic protein by the proteasome

Site-specific degradation of myelin basic protein by the proteasome

Studies on the inactivation of encephalitogenic myelin basic protein by serum.

This study confirms previous reports that myelin basic protein loses its encephalitogenic activity when incubated in normal serum at 37 degrees C. The mechanisms for this was studied. 125I-labelled human myelin basic protein was rapidly degraded by normal guinea pig serum to low molecular weight products as shown by polyacrylamide gel electrophoresis. An intermediate product of molecular weight about 6000 daltons was seen. Plasma had a much lower degradative activity than serum; the half life of myelin basic protein was 3.8 hours in plasma compared with 12 minutes in serum. Serum degraded myelin basic protein was no longer capable of suppressing experimental allergic encephalomyelitis in the guinea pig nor of eliciting delayed-type hypersensitivity in guinea pigs sensitized to myelin basic protein.

MMPs initiate Schwann cell-mediated MBP degradation and mechanical nociception after nerve damage

Matrix metalloproteinases (MMPs) emerge as modulators of neuropathic pain. Because myelin protects Aβ afferents from ectopic hyperexcitability and nociception from innocuous mechanical stimuli (or mechanical allodynia), we analyzed the role of MMPs in the development of mechanical allodynia through myelin protein degradation after rat and MMP-9−/− mouse L5 spinal nerve crush (L5 SNC). MMPs were shown to promote selective degradation of myelin basic protein (MBP), with MMP-9 regulating initial Schwann cell-mediated MBP processing after L5 SNC. Acute and long-term therapy with GM6001 (broad-spectrum MMP inhibitor) protected from injury-induced MBP degradation, caspase-mediated apoptosis, macrophage infiltration in the spinal nerve and inhibited astrocyte activation in the spinal cord. The effect of GM6001 therapy on attenuation of mechanical allodynia was robust, immediate and sustained through the course of L5 SNC. In conclusion, MMPs mediate the initiation and maintenance of mechanical nociception through Schwann cell-mediated MBP processing and support of neuroinflammation.

P25α Relocalizes in Oligodendroglia from Myelin to Cytoplasmic Inclusions in Multiple System Atrophy

p25alpha is an oligodendroglial protein that can induce aggregation of alpha-synuclein and accumulates in oligodendroglial cell bodies containing fibrillized alpha-synuclein in the neurodegenerative disease multiple system atrophy (MSA). We demonstrate biochemically that p25alpha is a constituent of myelin and a high-affinity ligand for myelin basic protein (MBP), and in situ immunohistochemistry revealed that MBP and p25alpha colocalize in myelin in normal human brains. Analysis of MSA cases reveals dramatic changes in p25alpha and MBP throughout the course of the disease. In situ immunohistochemistry revealed a cellular redistribution of p25alpha immunoreactivity from the myelin to the oligodendroglial cell soma, with no overall change in p25alpha protein concentration using immunoblotting. Concomitantly, an approximately 80% reduction in the concentration of full-length MBP protein was revealed by immunoblotting along with the presence of immunoreactivity for MBP degradation products in oligodendroglia. The oligodendroglial cell bodies in MSA displayed an enlargement along with the relocalization of p25alpha, and this was enhanced after the deposition of alpha-synuclein in the glial cytoplasmic inclusions. Overall, the data indicate that changes in the cellular interactions between MBP and p25alpha occur early in MSA and contribute to abnormalities in myelin and subsequent alpha-synuclein aggregation and the ensuing neuronal degeneration that characterizes this disease.