keratinfibrer

Keratinfibrer, or keratin fibril, is a filamentous structure formed by keratin proteins that contributes to the mechanical strength of epithelial tissues. In humans and other vertebrates, keratin fibrils are a major component of the cytoskeleton in keratinocytes and are especially important in keratinized tissues such as hair, nails, and the outer layer of skin.

Structure and assembly: Keratin proteins are intermediate filament proteins divided into type I (acidic) and type II (basic to neutral). In keratinocytes, type I and II keratins form heterodimers that align to create coiled-coil dimers, which assemble into protofilaments and then into 10-nm keratin intermediate filaments. In hair and nails, keratin fibrils aggregate into larger macrostructures, reinforcing the tissue with higher rigidity and resilience. Cross-linking through cysteine-rich disulfide bonds further strengthens hard keratin found in nails and certain regions of hair.

Function: Keratin fibrils distribute mechanical stress across cells and tissues, providing resistance to deformation from bending, stretching, and shear forces. They interact with desmosomes and other components of the cytoskeleton to maintain tissue integrity and barrier function. Keratin turnover and remodeling play roles in wound healing and epidermal maintenance.

Clinical relevance: Mutations in keratin genes can disrupt filament stability, leading keratinopathies such as epidermolysis bullosa simplex and pachyonychia congenita, characterized by fragile skin, nails, and mucous membranes. Understanding keratin fibrils aids in dermatology, biomaterials research, and cosmetic science, where keratin-based approaches are explored for therapies and tissue engineering.