Presence of gangliosides in the structure of membrane receptor for thyrotrophin.

Thyroid gangliosides were isolated from bovine thyroid tissue. Neutral lipids and glycolipids were removed by chromatography on a DEAE-cellulose column and residual acidic phospholipids by alkaline degradation. Thyroid gangliosides were separated by chromatography on a silica acid column into 9 different fractions. Thyroid gangliosides were found to be active in the inhibition of [125I]TSH binding to thyroid plasma membranes and this results from a direct action between thyrotrophin and gangliosides. The most active fraction contained gangliosides with two sialic acids per molecule. Pre-incubation of thyroid plasma membranes for 4 hours at 37 degrees C with gangliosides and removal of the unbound gangliosides increased the [125I]TSH binding to pre-treated membranes by 10-20%. Anti-ganglioside antibodies obtained by immunisation of rabbits inhibited [125I]TSH binding to thyroid plasma membranes by 60 to 80%. The thyroxine (T4) level in blood serum of immunized animals was significantly decreased after the first immunization and T4 become almost undetectable after the booster injection implying that antibodies against thyroid gangliosides produce severe impairment of thyroid cell function.