Filaggrin

• OMIM: 135940
• UniProt: P20930

As filaggrin are a group of mammalian proteins that are formed during the keratinization of the skin in the keratinocytes. Filaggrine help to link keratin filaments via disulfide bonds and thus have structure-building functions for the epidermis. Mutations in the FLG gene can be inherited forms of ichthyosis vulgaris and for susceptibility to atopic dermatitis type 2 lead at risk for allergies.

In a study of 3000 German school children with a mutation of the FLG gene was found in eight percent of the children. In later studies, these mutations with high IgE levels and risk of contact dermatitis, keratosis pilaris especially, xeroderma and nickel allergy were associated. As an additional factor of early exposure to cats was found in a British study.

Biosynthesis

In the keratohyalin granules of keratinocytes profilaggrin is expressed and stored. Profilaggrin is a 4000 amino acid protein that is highly phosphorylated and contains 23 filaggrin domains. Differentiation of the keratinocyte to the horny cell, profilaggrin is dephosphorylated and cleaved at the filaggrin domains apart, many 324 amino acids long filaggrin molecules. Since the profilaggrin contains 23 filaggrin domains that overlap, there are several ways to cut up a profilaggrin molecule. This explains the variety of possible Filaggrine.