Identification of beta-actin as a candidate autoantigen in autoimmune inner ear disease

Abstract

It has been shown that sera from patients with autoimmune inner ear disease contain antibodies to several inner ear antigens. We report here the characterization of the 42-43 kDa protein against which a significant number of patients' sera react strongly. After separation of inner ear proteins from guinea-pig cochleas by SDS-PAGE, the band corresponding to the 42-43 kDa protein was digested with trypsin and the peptide fragments were separated by high-performance liquid chromatography. Two fractions were then subjected to amino acid sequencing by the classical automated Edman degradation. The sequence of a stretch of 15 amino acids of the first fragment was identical to that of amino acids 148-162 of beta-actin. The sequence of the 10 amino acids of the second fragment was also identical to beta-actin. On Western blots, monoclonal antibody directed against beta-actin reacted with the inner ear 42-43 kDa proteins. The serum samples from the patients and the monoclonal antibody reacted with the non-muscle actin used as antigen in Western blotting. Immunoblot analysis of inner ear proteins after two-dimensional gel electrophoresis showed a spot, corresponding to the region of the 43 kDa as compared to the protein standards. On the basis of these data it is concluded that the target 42-43 kDa protein for antibodies in sera of patients with autoimmune inner ear disease is beta-actin, a molecule, which has important and numerous functions inside cells. This is the first report to identify the cytoskeletal protein beta-actin as a candidate autoantigen in autoimmune inner ear disease.

Sudden Deafness: Is It Viral?

“…Such antibodies have also been proposed as being responsible for so-called autoimmune inner ear disease. A number of putative inner ear antigens have been proposed as targets of such antibodies, including type 2 collagen [66] , ␤ -actin [67] , cochlin [68,69] , and ␤ -tectorin [69] . The best documented of these candidate antibodies is to choline transporter-like protein 2 (CTL2) [70] .…”

Proteomic analysis of cisplatin-induced cochlear damage: Methods and early changes in protein expression

“…This work has direct clinical application to perilymphatic fistulas. Several other laboratories have used 2D-gels to investigate inner ear autoimmune diseases (Billings et al, 1995;Boulassel et al, 2000;Harris et al, 1990), otoconia (Cao et al, 1996), glucocorticoid regulated inner ear gene expression (Yao et al, 1995), otosclerosis (Ribari et al, 1983), expression of chloride transport systems in auditory brainstem (Nothwang et al, 2003), analysis of the Coch gene (Ikezono et al, 2001), and calcium binding proteins of the cochlea (Winsky et al, 1989a,b).…”

Inner ear proteomics of mouse models for deafness, a discovery strategy

“…In bovine ear experiments, Ikezono et al demonstrated that the protein product of the Coch gene, which underlies the human deafness syndrome DFNA9 (Robertson et al, 1998), is abundant in the ear (Ikezono et al, 2004). 2DE has been applied in several other studies but with varying success (Boulassel et al, 2000). Other studies include localizations of individual proteins and functional determinations (Royaux et al, 2003), as well as correlation of expression of the actin filamentbundling protein espin with stereociliary bundle formation in the developing ear .…”