Proteins of the organ of Corti (OC)

Abstract

The majority of proteins found to date in OC were identified by immunohistological methods. While these techniques are powerful tools for localization of proteins, they frequently lack satisfactory specificity. Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) is able to demonstrate the presence in the OC of specific subtypes of certain proteins. In the case of contraction associated proteins, for instance, the presence of nonmuscle actin (beta and gamma), three types of nonmuscle tropomyosin (Tm:4, Tin:5, and Tm:8) and nonmuscle lactic dehydrogenase (LDH B) was documented. Another important role of 2D-PAGE is the demonstration of previously unknown proteins. The presence in the OC of two highly prominent proteins of low molecular weight and strongly acidic pH (assumed to be specific to the OC) was shown. Accordingly, they were termed OCP-I and OCP-II [I. Thalmann et al., Arch. Otorhinolaryngol. 226, 123–128 (1980)]. It was found that small amounts of OCP-I and OCP-II are present in spiral ligament and spiral limbus and more substantial amounts in basilar membrane. Neither protein is detectable in stria vascularis. Likewise, no proteins resembling OCP-I or OCP-II were found in tissues other than inner ear. While some biochemical features of the two proteins have in the meantime been characterized, their functional significance remains obscure. [Work supported by NIH.]

Genes and Hearing Loss: Relationship to Oxidative Stress and Free Radical Formation

“…The Fbxo2 gene encodes an F-box protein that is a member of these complexes and that interacts with client misfolded glycoproteins (Yoshida et al 2005 ). This protein was originally known as OCP1 and is present at high levels in the organ of Corti and brain (Thalmann et al 1997 ). Targeted mutation of Fbxo2 results in progressive hearing loss associated with degeneration of sensory and supporting cells in the cochlea and demonstrates a critical role for this stress response system in long-term maintenance of cochlear function (Nelson et al 2007 ).…”