Receptor-mediated endocytosis of alpha 2 macroglobulin by a glioma cell line.
Previous experiments have shown that human neoplastic and embryonic glial cell lines synthesize and secrete in culture, alpha 2 macroglobulin (alpha 2M), a broad spectrum proteinase inhibitor present in serum and extracellular fluids. The present study was aimed to investigate the presence of alpha 2M receptors on glial cell membrane, since several non-neural cell types producing alpha 2M also express alpha 2M receptors. By flow cytometric analysis, immunofluorescence and immunoelectronmicroscopy techniques we demonstrate an alpha 2M receptor-related immunoreactivity on the plasma membrane of a human glioma cell line. Ultrastructural experiments reveal a close colocalization of immunoreactivities for alpha 2M and its receptor in clathrin-coated pits and vesicles, structures typically involved in receptor-mediated endocytic pathways.
Nori
S L
SL
Institute of Human Anatomy, S. Cuore Catholic University, Rome, Italy.
Businaro
R
R
Fabrizi
C
C
Moestrup
S K
SK
Starace
G
G
Fumagalli
L
L
Lauro
G M
GM
D004705:Endocytosis / Q000502:physiology*; D005910:Glioma / Q000473:pathology; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D009457:Neuroglia / Q000166:cytology*; D011971:Receptors, Immunologic / Q000032:analysis*; D014407:Tumor Cells, Cultured; D000511:alpha-Macroglobulins / Q000032:analysis*
D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; D000511:alpha-Macroglobulins