Endocytosis and recycling of gangliosides in a human melanoma cell line: inhibitory effect of brefeldin A and monensin.

The internalization and recycling of glycosphingolipids (GLs), added exogenously to cells, has been shown in a number of systems. In addition, a portion of the internalized GLs becomes elongated by further glycosylation, presumably by passage through the Golgi apparatus, and is recycled to the plasma membrane. We have previously shown (K. Furukawa, I. Thampoe, H. Yamaguchi, and K. O. Lloyd J. Immunol. 142, 848, 1989) that NeuGc-LacCer (GM3), added exogenously to cultured human melanoma cells, is converted to NeuAc-NeuGc-LacCer (GD3) and appears at the cell surface where it can be recognized by a monoclonal antibody (32-27M) specifically recognizing this structure. The mechanism of this process has been investigated by analyzing the effect of monensin and Brefeldin A (BFA), two drugs known to affect vesicular transport and Golgi function, on the recycling of NeuGc-LacCer. Using two different serological assays, BFA was shown to specifically inhibit the recycling process. BFA probably achieves this effect by inhibiting the transfer of endocytosed GL from endosomes and the trans Golgi network to the Golgi stacks by a retrograde route and thus prevents its entry into the biosynthetic compartments. Monensin had a similar, but less clear-cut, effect on GM3 recycling. These results have important implications for understanding the modulation of cell surface glycolipids.