Degradation of tight junctions in HT29, a human colon adenocarcinoma cell line

The process of tight junction degradation was followed in a cell line of human colon adenocarcinoma. Tight junctions are degraded by 2 mechanisms: (1) breakdown of junctional elements to intramembrane particles; (2) bleb formation by which tight-junctional elements are internalized into the cytoplasm or excluded into the medium. It is suggested that the first mechanism allows preservation of membrane particles for re-use, whereas the second is a mechanism by which the cells eliminate unneeded junctional elements.