cytokerin

Cytokeratins are a group of fibrous cytoplasmic proteins that form the intermediate filament cytoskeleton of epithelial cells. They are part of the larger keratin family, which also includes hair and nail keratins. Cytokeratins are typically found in pairs, with a type I cytokeratin (acidic) and a type II cytokeratin (basic) co-assembling to form a stable heterodimer. These dimers then polymerize into filaments, contributing to the structural integrity and mechanical strength of epithelial tissues.

There are over 50 different types of cytokeratins, encoded by a large gene family. The specific type and combination of cytokeratins expressed in an epithelial cell are highly dependent on the cell's origin, differentiation state, and tissue type. This differential expression makes cytokeratins valuable as biomarkers in diagnostics, particularly in cancer pathology. For example, certain cytokeratin profiles can help identify the primary site of a metastatic tumor or distinguish between different types of carcinomas.

Cytokeratin filaments are anchored to cell junctions, such as desmosomes and hemidesmosomes, which connect cells to each other and to the extracellular matrix. This integration allows the cytoskeleton to withstand mechanical stress and maintain tissue architecture. Mutations in cytokeratin genes can lead to various inherited skin disorders, such as epidermolysis bullosa simplex, highlighting their critical role in cellular health and tissue function.