Polarized expression of an apical membrane glycoprotein is established before functional tight junctions have developed in MCF-7 cells.
A milk-fat globule membrane antigen, designated MAM-6 and detected immunocytochemically by the monoclonal antibody 115D8, is expressed apically in confluent MCF-7 monolayer cultures. Immediately after preparation of a single-cell suspension, MAM-6 appears on the entire cell surface. However, polarized apical expression of MAM-6 is restored as early as 2-6 hr after plating of unpolarized cells, before functional tight junctions are established, as judged by freeze-fracture and ruthenium red permeability. Quantitative immunogold cytochemistry reveals that the apical:basal ratio of MAM-6 expression was about 17:1 after 6 hr. Tight junctions developed as late as 12-24 hr after plating. At this time the apical:basal MAM-6 ratio was about 30:1 (as compared to about 50:1 in control monolayers).
Zou
Z Z
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Department of Anatomy, Panum Institute, University of Copenhagen, Denmark.
Petersen
O W
OW
van Deurs
B
B
D000951:Antigens, Neoplasm / Q000032:analysis; D001943:Breast Neoplasms; D002462:Cell Membrane / Q000648:ultrastructure*; D002463:Cell Membrane Permeability; D003599:Cytoskeleton / Q000502:physiology; D005614:Freeze Fracturing; D006801:Humans; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D007365:Intercellular Junctions / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000032:analysis / Q000096:biosynthesis*; D008854:Microscopy, Electron; D018396:Mucin-1; D012430:Ruthenium Red / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D008562:Membrane Glycoproteins; D018396:Mucin-1; D012430:Ruthenium Red