Gangliosides are Transported from the Plasma Membrane to Intralysosomal Membranes as Revealed by Immuno-Electron Microscopy

A biotin-labeled derivative of the ganglioside GM1 (biotin-GM1) was used to study its transport along the endocytic pathway of cultured fibroblasts by immuno-electron microscopy. Using electron dense endocytic tracers we could demonstrate that late endosomes and lysosomes of these cells are long living organelles with a high content of internal membranes. Our studies show that during endocytosis the biotin-GM1 was transported to these intraendosomal and intralysosomal membranes. These observations support the hypothesis that glycosphingolipids (GSL) are preferentially degraded in intralysosomal vesicles.