2024-02-21 09:37:13
Epithelial cells cover the surface of most of our organs in a carpet of cells. The intestine, for example, is covered in cells, most of which absorb the nutrients we ingest. These cells are joined together by three types of junctions which coexist and provide different functions, ranging from the selective filtration of certain ions to the mechanical maintenance of the epithelial layer. These junctions, the tight junction, the adherens junction, also called zonula adherens, and desmosomes, were discovered in the 1960s and their constituent elements as well as their organization were proposed during the 1980s and 1990s, forming the basic knowledge of biology students even today! The adherens junction in particular is established as being organized into a belt of membrane-anchored adhesion proteins, cadherins, and supported by filaments, actin filaments. This junction has an important mechanical role in the cell, for example by impacting the shape of the cell.
A new category of cell junctions to better understand epithelial cell adhesion and mechanics
By observing the adherens junction of epithelial cells obtained from human intestinal biopsies, or from human cells in culture using an optical microscopy method that is more resolved than traditional techniques, scientists have made a very surprising discovery. In immature cells, the junction follows the established model, but in mature cells which cover the intestinal villi, the adherens junction is actually formed of two belts of different adherens proteins: one belt does contain cadherins, but the other girdle is completely devoid of them and contains another type of adhesion cells, nectins.
Another surprise is that the support filaments are not close to the cadherin belt, but to those of nectins, indicating that the mechanical support in the adherens junctions is probably supported by nectins rather than cadherins, overturning yet another belief. 40 years old. In reference to the established nomenclature, the authors name this new organization the mature adherent zonula.
These results are important for better understanding the adhesion and mechanics of epithelial cells. These two essential characteristics of epithelia are particularly affected in cancers of epithelial origin, which represent 80% to 90% of current cancers.
© Pierre Mangeol
Figure : Models of mature and immature intestinal cell junctions.
Learn more:
The mature adherent zonula redefines the apical junction of intestinal epithelia. Pierre Mangeol, Dominique Massey-Harroche, Michael Sebbagh, Fabrice Richard, André Le Bivic, and Pierre-François Lenne. February 20, 2024. PNAS.https://doi.org/10.1073/pnas.231672212
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#category #cell #junctions #intestine
