Читать книгу Introduction to the Human Cell - Danton PhD O'Day - Страница 26

When they were originally discovered cell junctions were considered to be relatively static structures. This was likely because they appeared to have a consistent, unchanging structure when viewed with the electron microscope. New techniques have revealed that proteins can move in and out of these junctions allowing the cell to sense the status of its intercellular adhesions. For example, occludin and ZO1, two proteins from tight junctions have been shown to move into the nucleus to regulate gene activity. Proteins that move between adhesion complexes have been termed NACos (Nucleus and Adhesion Complexes). β-catenins are the most well-studied NACos. The following graphics show what happens when an adherens junction is disrupted (Figure 3.10).

Figure 3.10. Beta-catenins can move from disrupted tight junctions into the nucleus to regulate gene transcription.

A. Intact cells, B. One cell (left side) is damaged. C. β-catenins enter nucleus to regulate gene transcription.

If epithelial tissues become disrupted such as by a cut in the skin or tear in the intestinal lining, it would lead to the disruption of adherens junctions in adjacent cells in turn releasing ß-catenins as well as other junctional proteins. The ß-catenins can then travel to the nucleus to initiate gene transcription to stimulate cell cycle events or other processes required in wound healing. A similar event happens when tight junctions are disrupted by a bacterial infection as discussed in the next section.