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The M2 autoantigen of central nervous system myelin, a glycoprotein present in oligodendrocyte membrane
Abstract:
Autoantibodies with in-vitro demyelinating capacity induced in Hartley and strain 13 guinea pigs with homologous central nervous system (CNS) tissue were used to characterize the target autoantigen M2. Using the Dot Immunobinding technique, M2 was found to be a component of CNS myelin different from basic protein (BP) and from cerebroside. The expression of M2 on oligodendrocytes, cells known to produce CNS myelin, also confirmed that M2 was a component of CNS myelin. Furthermore, the autoradiography of immunoprecipitates formed with radiolabelled guinea pig myelin and analysed in sodium dodecyl sulphate gels showed that M2 was specific to CNS myelin and absent in peripheral nervous system (PNS) myelin. On electrophoresis M2 appeared as two CNS myelin protein bands at the 27 and 54 KD molecular weight levels, distinct from the major protein bands of proteolipid and BP. M2 bands were of glycoprotein nature, as was demonstrated by affinity chromatography of CNS myelin on wheat germ agglutinin (WGA)-Sepharose. A monoclonal antibody induced by BP-free CNS glycoproteins recognized the same bands as anti-M2 serum in guinea pig CNS myelin. This would imply that both M2 bands share common determinants. M2 bands similar to the above in guinea pig were also shown in rat, rabbit and bovine CNS myelin with guinea pig antibodies. The same type of anti-M2 antibodies were induced in rabbit immunized with homologous CNS tissue. Although only a minor component of myelin, M2 is strongly immunogenic compared to BP. M2 antigen could thus be the target of chronic demyelinating processes such as experimental allergic encephalomyelitis.
Insights
Researchers identified M2, a novel autoantigen in central nervous system (CNS) myelin, distinct from known proteins. This immunogenic glycoprotein may be a key target in demyelinating diseases like experimental allergic encephalomyelitis.
Area of Science:
- Neuroimmunology
- Myelin Biology
- Autoimmunity
Background:
- Autoantibodies capable of in-vitro demyelination were generated in guinea pigs using central nervous system (CNS) tissue.
- These autoantibodies were used to identify and characterize the M2 autoantigen within CNS myelin.
Purpose of the Study:
- To characterize the M2 autoantigen, a target of demyelinating autoantibodies.
- To determine the composition and specificity of the M2 antigen within the CNS myelin.
Main Methods:
- Dot Immunobinding assays to identify M2 as a distinct myelin component.
- Analysis of immunoprecipitates via SDS-PAGE and autoradiography to assess M2 specificity.
- Affinity chromatography using wheat germ agglutinin (WGA)-Sepharose to determine M2's glycoprotein nature.
- Immunization of rabbits with CNS tissue to induce anti-M2 antibodies.
Main Results:
- M2 was identified as a component of CNS myelin, separate from basic protein (BP) and cerebrosides.
- M2 expression was confirmed on oligodendrocytes, the cells responsible for CNS myelin production.
- Autoradiography revealed M2 is specific to CNS myelin and absent in peripheral nervous system (PNS) myelin.
- Electrophoresis showed M2 as two distinct glycoprotein bands (27 and 54 KD) in CNS myelin.
- Anti-M2 antibodies cross-reacted with M2 bands in various species, including rat, rabbit, and bovine CNS myelin.
Conclusions:
- M2 is a CNS-specific myelin glycoprotein with shared determinants, distinct from major myelin proteins.
- Despite being a minor component, M2 is highly immunogenic, suggesting its potential role as a target in chronic demyelinating diseases.
- M2 represents a significant candidate autoantigen in conditions like experimental allergic encephalomyelitis.