Cornified envelope

Membrane-like, 15 nm thick, dense and very poorly soluble structure on the inner side of the cell membrane of corneocytes. It thus forms a protective barrier against environmental factors that is difficult to penetrate. The "cornified envelope" is composed of numerous proteins. These include: filaggrine, involucrine, loricrine, small proline rich proteins (SPR), repetin, etc. The genes of these proteins are all located in the cluster of the epidermal differentiation complex (EDC), which is located in the region of chromosome 1q21. The CE develops during keratinization, which can be described as a special form of controlled, physiological apoptosis.

It is assumed that increasing Ca concentrations trigger a cross-linking of involucrine molecules among themselves, which are bound to the inner cell membrane. They thus form the basic structure. In a second step, mainly loricrin and SRPs, and other proteins such as repetin, are connected to the backbone by transglutaminases via disulfide bridges and N-(γ-glutamyl)-lysine isodipeptide bonds. Mutations in the gene for transglutaminase 1 (TGM1) lead to a distinct disorder of keratinization (see below: Autosomal recessive ichthyosis with transglutmaninase deficiency). Keratin intermediary filaments and filaggrin form complexes which are also cross-linked with the CE and thus represent the main mass of terminally differentiated keratinocytes.

1. Harding CR et al (2003) The cornified cell envelope: an important marker of stratum corneum maturation in healthy and dry skin. Int J Cosmet Sci 25: 157-167