Ultrastructural localization of gangliosides; GM1 is concentrated in caveolae.
The ultrastructural distribution of the ganglioside GM1 was investigated in A431 cells. After fixation, the cells were frozen in liquid nitrogen, freeze-substituted, and then embedded in Lowicryl resin at -45 degrees C. By use of the cholera toxin-binding subunit adsorbed to gold as a specific probe to label on the sections, GM1 was shown to be present in endocytic organelles, in the trans-Golgi network, and on the plasma membrane, but was not detectable in the endoplasmic reticulum. GM1 was not distributed uniformly over the plasma membrane but was concentrated approximately four-fold in non-coated invaginations. These were identified as caveolae by labeling frozen sections of cholera toxin-gold surface-labeled cells with antibodies to VIP-21/caveolin. The results strengthen the functional analogy between caveolae and sorting domains of the TGN in polarized epithelial cells.
Parton
R G
RG
European Molecular Biology Laboratory, Heidelberg, Germany.
D002352:Carrier Proteins / Q000378:metabolism; D051242:Caveolin 1; D022461:Caveolins; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure*; D002772:Cholera Toxin; D004705:Endocytosis; D017110:Freeze Substitution; D005677:G(M1) Ganglioside / Q000378:metabolism*; D017979:Gold Colloid; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism; D008854:Microscopy, Electron / Q000379:methods; D015388:Organelles / Q000378:metabolism / Q000648:ultrastructure; D016610:Tissue Embedding; D014407:Tumor Cells, Cultured
C495540:CAV1 protein, human; D002352:Carrier Proteins; D051242:Caveolin 1; D022461:Caveolins; D017979:Gold Colloid; D008024:Ligands; D008565:Membrane Proteins; D005677:G(M1) Ganglioside; D002772:Cholera Toxin