keratiner

Keratiner, or keratins, are a family of fibrous structural proteins that form the intermediate filaments of epithelial cells. In vertebrates, keratins are divided into type I (acidic) and type II (basic to neutral) keratins. They are expressed as pairs of type I and type II keratins that co-assemble into 10-nm intermediate filaments, providing mechanical support and a protective barrier to epithelial tissues. Keratins are highly expressed in keratinized structures such as the skin, hair, nails, hooves, feathers, and beaks. In mammals, alpha-keratins predominate; in birds and reptiles, beta-keratins (corneous beta-proteins) are common.

The genes encoding keratins form large multigene families, with expression that is tissue- and differentiation-specific. Keratins assemble as heterodimers and progress to filament networks that stabilize cells against mechanical stress. This network also contributes to the barrier function of the epidermis, helping control water loss and protective defense against environmental damage.

Clinical significance arises from keratin gene mutations that disrupt filament assembly, leading to keratinopathies such as epidermolysis bullosa simplex (often caused by mutations in KRT5 or KRT14) and various keratin-related hair and skin disorders. These conditions typically manifest as skin fragility, dystrophy, or abnormal hair and nail growth.

Industrial and cosmetic uses include extracting keratins from keratin-rich waste (such as feathers and hair) to produce biomaterials, films, or hydrogels. In cosmetics and hair care, keratin-containing treatments aim to replenish or reshape keratin in the hair shaft, though effects are often temporary and depend on the overall hair care regimen.

Etymology derives from Greek keros, “horn,” reflecting the horn-like properties of keratinized tissues.