Opalin Protein <table class="infobox infobox-protein">Protein Name </td>Gene </td>UniProt ID </td>Gene Symbol </td>Chromosomal Location </td>PDB Structure </td>Molecular Weight </td>Subcellular Localization </td>Protein Family </td>Expression </td>
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Opalin Protein <table class="infobox infobox-protein">Protein Name </td>Gene </td>UniProt ID </td>Gene Symbol </td>Chromosomal Location </td>PDB Structure </td>Molecular Weight </td>Subcellular Localization </td>Protein Family </td>Expression </td>
Opalin (also known as Temporin-1 or OPALIN ) is a highly glycosylated transmembrane protein predominantly expressed in the central nervous system (CNS) by mature oligodendrocytes. First identified in 2005, Opalin represents one of the most abundant myelin-specific proteins in the human brain, second only to myelin basic protein (MBP) in copy number per myelin sheath. While primarily studied in the context of multiple sclerosis and white matter disorders, emerging research suggests Opalin and other myelin proteins may have broader implications for neurodegenerative diseases characterized by white matter abnormalities.
Protein Overview
Structure Opalin possesses several distinctive structural features:
Primary Structure
N-terminal signal peptide : Directs protein to the secretory pathwayLarge extracellular domain : 1,500+ amino acids with extensive O-linked and N-linked glycosylationSingle transmembrane helix : Type I membrane protein topologyShort cytoplasmic tail : ~30 amino acids containing potential phosphorylation sitesGlycosylation Opalin is one of the most heavily glycosylated myelin proteins:
O-linked glycosylation : Predominantly in the extracellular domain, contributing to the protein's large apparent molecular weightN-linked glycosylation : Multiple potential N-glycosylation sites (N-X-S/T motifs)Glycosylation function : Mediates protein-protein interactions, protects from proteolysis, and may regulate immune recognition[@kreitman2020]Post-translational Modifications
Phosphorylation : Cytoplasmic tail contains serine/threonine residues that may be phosphorylatedFatty acid acylation : Potential palmitoylation sites for membrane associationProteolytic processing : May undergo shedding of the extracellular domainNormal Function
Myelin Formation and Maintenance Opalin plays essential roles in central nervous system myelination:
Myelin assembly : Incorporated into the multilamellar myelin sheath during active myelinationMyelin stability : Contributes to long-term maintenance of myelin integrityOligodendrocyte maturation : Serves as a specific marker for mature, myelinating oligodendrocytesNode of Ranvier organization : Localizes to paranodal regions where it may interact with axonal proteins[@rosenbluth2018]
Molecular Interactions Opalin interacts with several myelin-related proteins:
Myelin basic protein (MBP) : May co-localize in the cytoplasmic leaflet of myelinMyelin oligodendrocyte glycoprotein (MOG) : Co-expressed in mature oligodendrocytesPLP/DM20 : Lipid-rich myelin proteins with complementary functionsContactin : Paranodal cell adhesion molecule interactionsPhysiological Significance
Saltatory conduction : Myelin enables rapid action potential propagationMetabolic support : May facilitate axonal energy metabolism through glial-neuronal interactionsNeuroprotection : Intact myelin provides trophic support to underlying axonsRole in Neurodegenerative Diseases
Multiple Sclerosis (MS) Opalin has been extensively studied in MS, a demyelinating disease:
Demyelination marker : Loss of Opalin immunoreactivity in chronic lesionsRemyelination marker : Re-expression in remyelinating oligodendrocytesBiomarker potential : Opalin in cerebrospinal fluid may reflect oligodendrocyte death[@michailidou2022]Therapeutic target : Promotes remyelination in experimental modelsWhite Matter Disorders Various leukodystrophies involve Opalin dysfunction:
Metachromatic leukodystrophy (MLD) : Arylsulfatase A deficiency leads to sulfatide accumulation affecting myelinAdrenoleukodystrophy (ALD) : Very-long-chain fatty acid accumulation causes myelin breakdownAlexander disease : [GFAP](/entities/gfap) mutations lead to Rosenthal fiber formation affecting white matter[@pouwels2019]Neurodegenerative Conditions with White Matter Involvement While primarily a myelin protein, Opalin alterations are observed in:
Alzheimer's Disease
White matter hyperintensities are common in AD
Vascular contributions to cognitive impairment and dementia (VCID)
Oligodendrocyte dysfunction precedes neuronal loss
Myelin breakdown releases toxic lipids affecting [neurons](/entities/neurons)[@bartzokis2021]
Parkinson's Disease
Multiple system atrophy (MSA) shows prominent white matter involvement
Opalin expression may be altered in MSA-C (cerebellar type)
Demyelination contributes to parkinsonian symptoms
Amyotrophic Lateral Sclerosis
White matter abnormalities in corticospinal tracts
Oligodendrocyte dysfunction contributes to motor neuron degeneration
Opalin may serve as a marker of oligodendrocyte involvement[@philips2020]
Ischemic White Matter Injury
Vascular dementia involves subcortical white matter ischemia
Chronic hypoperfusion leads to myelin loss
Opalin expression decreases in chronic white matter lesions
Therapeutic Targeting
Remyelination Strategies
Opalin-promoting compounds : Small molecules that enhance Opalin expressionCell transplantation : Oligodendrocyte precursor cell (OPC) transplantation with Opalin as differentiation markerGene therapy : Viral vectors expressing Opalin for remyelination
Biomarker Development
CSF Opalin : Biomarker for demyelination and remyelinationBlood Opalin : Peripheral marker under developmentImaging : PET ligands targeting myelin proteins (investigational)Challenges
[BBB](/entities/blood-brain-barrier) penetration : Therapeutic agents must reach white matterTiming : Remyelination strategies most effective early in diseaseSpecificity : Targeting specific oligodendrocyte populations
Myelin as a Therapeutic Target Understanding Opalin function has broader implications:
Neuroprotection
Myelin degradation releases toxic lipids and iron
Preserving myelin protects axons from degeneration
Myelin repair may prevent secondary neuronal loss
Combination Therapies
Myelin repair combined with neuroprotection
Immunomodulation to reduce ongoing demyelination
Neuronal support to enhance functional recovery
Model Systems
Transgenic mice : Opalin knockout and reporter linesiPSC-derived oligodendrocytes : Human oligodendrocyte differentiation protocolsOrganotypic slice cultures : Myelin maintenance and repair studiesExperimental Approaches
Proteomics : Myelin protein composition analysisTranscriptomics : Oligodendrocyte maturation profilingSingle-cell RNA-seq : Heterogeneity of oligodendrocyte lineagesSummary Opalin represents a critical myelin protein with specific expression in mature oligodendrocytes. While most extensively studied in the context of demyelinating diseases like multiple sclerosis, its role in broader neurodegenerative processes is increasingly recognized. White matter abnormalities are a common feature of many neurodegenerative conditions, and understanding myelin protein biology offers opportunities for therapeutic intervention. Future research should focus on developing Opalin-based biomarkers, enhancing remyelination strategies, and understanding the interplay between myelin dysfunction and neuronal degeneration.
See Also
[Proteins Index](/proteins)
[Myelin Proteins Overview](/content/proteins)
[Oligodendrocyte Biology](/cell-types/oligodendrocytes)
[Multiple Sclerosis](/diseases/multiple-sclerosis)
White Matter Disorders
[Demyelination Mechanisms](/content/mechanisms)
[Multiple System Atrophy](/diseases/multiple-system-atrophy)
External Links
[UniProt - OPALIN (Q9BZE4)](https://www.uniprot.org/uniprot/Q9BZE4)
[GeneCards - OPALIN](https://www.genecards.org/cgi-bin/carddisp.pl?gene=OPALIN)
[NCBI Gene - OPALIN](https://www.ncbi.nlm.nih.gov/gene/130814)
References
[Yoshikawa et al., Identification of Opalin: a novel myelin protein (2005) (2005)](https://doi.org/10.1002/cne.20767))
[Simons et al., Myelin biology and disorders (2017) (2017)](https://doi.org/10.1093/brain/awx146))
[Unknown, Nave & Werner, Myelin Elongation and the Role in Neurodegeneration (2014) (2014)](https://doi.org/10.1016/j.neuroscience.2014.01.035))
[Kreitman et al., Glycosylation of myelin proteins (2020) (2020)](https://doi.org/10.1002/cne.24873))
[Rosenbluth et al., Paranodal organization and function (2018) (2018)](https://doi.org/10.1002/cne.24395))
[Michailidou et al., CSF biomarkers in demyelinating disease (2022) (2022)](https://doi.org/10.1016/j.jneuroim.2022.577859))
[Pouwels et al., White matter disorders: classification (2019) (2019)](https://doi.org/10.1093/brain/awz054))
[Bartzokis et al., Myelin as a therapeutic target in Alzheimer's disease (2021) (2021)](https://doi.org/10.1016/j.neurobiolaging.2021.02.012))
[Philips et al., Oligodendrocyte dysfunction in ALS (2020) (2020)](https://doi.org/10.1093/brain/awaa213)) Show full description