Involucrin: A Constituent of Cross-Linked Envelopes and Marker of Squamous Maturation

The document discussed the role of involucrin as a component of cross-linked envelopes in squamous cells, which were crucial for the maturation and protective function of the epidermis. These envelopes, found beneath the plasma membrane, were resistant to various chemical agents but sensitive to proteolytic digestion. Their chemical stability was due to ε-(γ-glutamyl)lysine cross-linking from transglutaminase activity. Involucrin was present in the stratified squamous epithelia of humans and other mammals, contributing to the structural integrity of hair and nails. The study highlighted involucrin as a marker for keratinocyte differentiation, emphasizing its importance in the formation of the cornified envelope during terminal differentiation.