Immunohistochemical localization of G protein βγ subunits in the lateral wall of the rat cochlea

Abstract

The role of G protein-mediated signal transduction in the production of endolymph, an extracellular fluid of unusual ionic composition, is beginning to be understood. The identity of G α subunits in the stria vascularis and the spiral ligament of the lateral wall of the cochlear duct is well established. However, little is known about the presence of βγ subunits. This study used immunohistochemistry to investigate the distribution of G protein βγ subunits in the lateral wall of the cochlea. Temporal bones of 6-to 8-week-old rats were fixed in 4% paraformaldehyde and 0.1% glutaraldehyde and processed for embedding in paraffin wax. The dewaxed, midmodiolar sections of the cochlea were incubated with subunit-specific polyclonal antibodies. The results show that the pattern of immunoreactivity varies for the G protein β 1-4 and γ 1-3, 5 and 7 subunits in the stria vascularis and spiral ligament. In the stria vascularis, immunoreactivity was detected for β 2, β 3, β 4, γ 1, γ 2 and γ 7 subunits. All five types of fibrocytes in the spiral ligament exhibited positive staining for γ 2 and γ 7. However, immunoreactivity for β 1-4 subunits was variable.Immunoreactivity for γ 3 and γ 5 subunits was not detected in the lateral cochlear wall. The expression pattern of G protein βγ subunits in lateral wall provides a basis for interpreting the functions of G protein-coupled receptors in cochlear fluid homeostasis.

Mouse G-protein gamma3 expression in the developing CNS and neural crest cell derivatives

“…1), it is interesting to note that γ3 protein was not detected in the lateral chochlear wall of the adult rat (Khan et al, 2006). Rather than differences in staining between two closely related species, this discrepancy is likely a sensitivity issue between the immunocytochemistry methodology used by Khan et al (2006), PCR in the study by Barritt et al (1999) and in situ hybridization used in this study. Detailed analysis from cryosectioned material also showed γ3 expression in the nose (Fig.…”