Gangliosides are glycolipids mostly located in the plasma membrane (PM). Antibodies to GM1 ganglioside are present in patients with Guillain-Barré neuropathy syndrome (GBS) and in a rabbit model of this disease. In this work, we investigated in different cell lines the binding and intracellular fate of affinity purified IgG and IgM antibodies to GM1 (GM1Ab) obtained from a rabbit model of GBS in comparing with the transport of cholera toxin (CT), which binds with a high affinity GM1. We demonstrated that in GM1-expressing CHO-K1 cells, GM1Ab is endocytosed and accumulated at the endocytic recycling compartment. Then, internalized GM1Ab is recycled back to the PM. Endocytosed GM1Ab colocalized to some extent with co-endocytosed CT at early and recycling endosomes, but not in Golgi and endoplasmic reticulum, where CT was also located. GM1Ab, in contraposition to CT, showed a reduced internalization in COS-7 cells and neuronal cell lines AH-SY5Y and Neuro2a. Results from photobleaching experiments revealed an inverse correlation between the efficiency of endocytosis and lateral mobility of GM1Ab in PM from these cell lines. Results indicate that GM1Ab and CT are differentially endocytosed and sorted, providing the basis to gain further insight into the mechanisms that operates in the intracellular trafficking and pathological effect of CT and neuropathy-associated antibodies.
