Gangliosides are glycolipids mainly located in the plasma membrane. Antibodies to ganglioside have been associated with a wide range of clinically identifiable acute and chronic neuropathy syndromes. Particularly, antibodies to GM1 ganglioside are present in patients with Guillain-Barré syndrome (GBS) and in a rabbit model of this disease. In this work, we investigated the binding and intracellular fate of internalized IgG antibodies to GM1 (from rabbit model of GBS) in CHO-K1 cells expressing GM1. We demonstrate that antibodies to GM1 are rapidly and specifically endocytosed by CHO-K1 cells. After internalization, the antibodies transit sorting endosomes to accumulate at the endocytic recycling compartment, almost no colocalizing with lysosomes marker. About 50% of the endocytosed anti-GM1 was recovered from the culture medium. Interestingly, this endocytic recycling route was only partially followed by cholera toxin (CTx), a toxin which tightly binds GM1. Briefly, endocytosed anti-GM1 colocalized with co-endocytosed CTx in recycling endosomes but not in Golgi and ER, where CTx was also found to reside. Moreover, CTx did not recycle to the culture media. Thus, the results indicate that anti-GM1 is endocytosed, accumulated in recycling endosome and transported back to the plasma membrane in a fate different from the intracellular transport of another GM1 binding molecule, as CTx.
