Question

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in part A of Figure 11-35. Which type of defect described below is the most likely to cause the redistribution of that protein around the entire cell, shown in part B of Figure 11-35?

Answer 1

A defect in tight junctions is likely responsible for the redistribution of an apical protein in epithelial cells, as these junctions maintain cell polarity by limiting protein movement across the cell surfaces.

Step-by-step explanation:

The most likely defect causing the redistribution of an apical protein around the entire cell is a malfunction of the tight junctions. These junctions have a critical role in maintaining the polarity of epithelial cells by preventing the movement of proteins between the apical and basal surfaces. When tight junctions are compromised, proteins can diffuse laterally, leading to a loss of polarity and the observed redistribution.

The apical domain faces the lumen or the external environment, and this localization is essential for the cells' specific roles, which include secretion. Defects in anchoring junctions, such as desmosomes, adherens, and hemidesmosomes, influence cell attachment and structural integrity but do not primarily affect protein localization between apical and basal surfaces. Hence, the malfunctioning of tight junctions is most likely responsible for the mislocalization of the protein.