Redistribution of surface macromolecules in dissociated epithelial cells

Area of Science:

• Cell Biology
• Epithelial Cell Biology
• Biochemistry

Background:

• Epithelial cells possess specialized apical and basolateral membrane domains.
• The mechanisms maintaining this surface specialization are not fully understood.
• Glycoproteins are key components of the cell surface.

Purpose of the Study:

• To investigate the role of tight junctions in maintaining epithelial cell surface specialization.
• To characterize the apical surface coat material in frog urinary bladder epithelial cells.

Main Methods:

• Ultrastructural and cytochemical techniques including high-resolution autoradiography ([3H]glucosamine, [3H]fucose), 125I iodination, concanavalin A-peroxidase, periodic acid-chromic acid silver methenamine, and colloidal thorium.
• Study of intact and dissociated frog urinary bladder epithelial cells.

Main Results:

• The apical surface coat material (likely glycoprotein) differs from that on lateral and basal surfaces.
• In dissociated cells, the apical material invades opened tight junctions within 5 minutes.
• The apical material progressively spreads to lateral (40 min) and basal (80 min) membranes after tight junction opening.

Conclusions:

• Tight junctions act as a barrier, confining apical surface material when intact.
• The opening of tight junctions allows apical material to migrate to other cell surfaces.
• Tight junctions are crucial for maintaining distinct apical and basolateral cell surface domains in epithelia.