Identification and localization of the GM1 ganglioside in the cochlea using thin-layer chromatography and cholera toxin.

Abstract

Using high-performance thin-layer chromatography, we identified GM1, GM3, GD3, GD1a, GT1b, GQ1b, and other gangliosides in chinchilla cochlea and cerebellum. GM1 was also identified on chromatograms with the B-subunit of cholera toxin (BCT). BCT was also used to determine the distribution of GM1 in fixed and unfixed tissues from cochlea, cerebellum, and sciatic nerve. Positive control tissues showed expected labeling of GM1 by BCT. Negative controls showed expected suppression of BCT binding to GM1 after GM1 extraction and GM1 absorption. In the cochlea, GM1 appeared abundant in plasma membranes of most epithelial cells lining the endolymphatic surface of the scala media, including the interdental, inner supporting, pillar, Deiters, Hensen, Claudius, Boettcher, spiral prominence, and external sulcus. GM1 appeared less abundant in cells of the stria vascularis, Reissner's membrane, and in nerve fibers. In hair cells, the stereocilia appeared to contain GM1; however, the endolymphatic surface of the cuticular plate and the body of the outer hair cells appeared to contain little GM1. In addition, the tectorial membrane, connective tissue of the spiral limbus, and amorphous layer of the basilar membrane also appeared to contain little GM1. Enzymatic degradation of glycoproteins and transformation of polysialogangliosides to GM1 increased the reactivity of BCT to cochlear GM1. This further supported the presence of GM1 and other gangliosides in the cochlea. Although the functional significance of GM1 and other gangliosides in the cochlea is not yet known, they are likely to play important roles in membrane function.