Endocytosis of wheat germ agglutinin binding sites from the cell surface into a tubular endosomal network

摘要: By using fluorescence and electron microscopy, the endocytic pathway encountered by cell surface components after they had bound wheat germ agglutinin (WGA) was visualized. The majority of these are thought to consist sialylated glycoproteins (HMWAG) that represent a subpopulation total proteins but most externally disposed plasma membrane cell. Examination semi-thin sections medium- high-voltage microscopy revealed three-dimensional organization vesicular tubular endosomes. Binding either fluorescein isothiocyanate-, horseradish peroxidase-, or ferritin-conjugated WGA cells at 4 degrees C showed HMWAG were distributed uniformly over surface. Warming surface-labeled 37 resulted in endocytosis into peripheral endosomes via invagination regions both coated uncoated membrane. endosome appeared as isolated complexes comprising element (300-400 nm diam.) surrounded continuous with cisternae (45-60 diam.), which did not interconnect After 30 min more label also became localized network anastomosing tubules located centrosomal region Endocytosed WGA-HMWAG become associated Golgi apparatus, although noted vicinity trans-Golgi region. accumulation within inhibited when incubated 18 C. None compartments contained acid phosphatase activity, result is consistent other data do pass through lysosomes initially. kinetics labeling interpretation recycling binding occurred rapidly from early followed late compartment. In conclusion, portion routed complex arrangement following includes putative post-endosomal, reticulum appears be separate trans-most saccule.