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Receptor‐mediated endocytosis and recycling of alpha‐fetoprotein in human B‐lymphoma and T‐leukemia cells
Author(s) -
Torres Juan M.,
Geuskens Maurice,
Uriel Jose
Publication year - 1991
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910470120
Subject(s) - endocytosis , lymphoma , cancer research , leukemia , receptor mediated endocytosis , receptor , medicine , alpha (finance) , biology , immunology , construct validity , nursing , patient satisfaction
The kinetics of iodinated human alpha‐fetoprotein (AFP) binding and uptake by 2 human neoplastic lymphoid cell lines (CEM and RAJI) have been studied. Three saturation plateaus were obtained by incubating CEM and RAJI cells at 4°C with 125 I‐AFP at different concentrations. Scatchard analysis suggested the presence of 3 types of receptor site with different affinities and capacities on cells of both lines. AFP binding was inhibited by unlabelled human and bovine AFP, and to a lesser extent by human serum albumin (SAH); no significant competition was observed with human transferrin (Tf) or ovalbumin (Ova). Pulse‐chase experiments showed that 125 I‐AFP was released practically undegraded from the cells. Covalent conjugates of AFP and Tf with horseradish peroxidase (HRP) were used to follow the endocytosis and intracellular pathway of these serum proteins by electron microscopy. Both proteins were observed in coated vesicles, endosomes and a tubular vesicular network localized in the Golgi‐centrosphere region. SAH‐HRP was internalized to a much lesser extent. Ova‐HRP was poorly internalized and was observed in lysosome‐like organelles.