Tonofilaments

Tonofilaments are a type of intermediate filament found in epithelial cells. They are composed of a variety of proteins, with cytokeratins being the most common. These filaments form a dense network throughout the cytoplasm, anchoring to desmosomes and hemidesmosomes, which are specialized cell junctions. This structural role provides mechanical strength and resilience to epithelial tissues, allowing them to withstand physical stress.

The composition of tonofilaments can vary depending on the specific type of epithelial cell and the tissue in which it is found. For example, different cytokeratin proteins are expressed in epidermal cells compared to those in the digestive tract. This diversity in protein composition contributes to the specialized functions of different epithelial tissues.

The presence and arrangement of tonofilaments are crucial for maintaining the integrity and barrier function of epithelial layers. Disruptions in tonofilament structure or protein assembly can lead to cellular fragility and contribute to various diseases, including certain skin disorders and cancers. Their role in cell adhesion and mechanical stability makes them a significant component of the cellular cytoskeleton.