Myelin protein Po as a potential autoantigen in autoimmune inner ear disease.

We have previously shown that a 30,000 Mr protein extracted from guinea pig inner ear tissue is recognized by autoantibodies present in the serum of patients suffering from autoimmune inner ear disease. This protein was localized in the modiolus and in the organ of Corti. We have now identified this protein by a combination of microsequencing and matrix-assisted laser desorption ionization time-of-flight mass spectrometry of its tryptic peptides. A partial sequence of the protein was thereby determined. These data and 2-dimensional gel electrophoresis followed by immunoblotting experiments showed that the 30,000 Mr inner ear antigen is the major peripheral myelin protein Po. This suggests that protein Po may be an important autoantigen in autoimmune inner ear disease.