Figure 165

Immunofluorescent localization of proteins of the tight junction after ATP depletion and repletion. The cytosolic protein zonula occludens 1 (ZO-1), and the transmembrane protein occludin are integral components of the tight junction that are intimately associated at the apical border of epithelial cells. This is demonstrated here by indirect immunofluorescent localization of these two proteins in normal kidney epithelial cells. After 1 hour of ATP depletion this association appears to change, occludin can be found in the cell interior, whereas ZO-1 remains at the apical border of the plasma membrane. Interestingly, the intracellular distribution of the actin-cytoskeletal-associated protein fodrin also changes after ATP depletion. Fodrin moves from a random, intracellular distribution and appears to become co-localized with ZO-1 at the apical border of the plasma membrane. These changes are completely reversible after ATP repletion. These findings suggest that disruption of the permeability barrier could be due, at least in part, to altered association of ZO-1 with occludin. In addition, the apparent co-localization of ZO-1 and fodrin at the level of the tight junction suggests that ZO-1 is becoming intimately associated with the cytoskeleton.

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