Expression and function of the keratinocyte integrins.

Human keratinocytes express several adhesive receptors of the integrin family. Expression is normally confined to the basal (proliferative) layer of keratinocytes, both in mature epidermis and during development. Altered expression patterns are observed during wound healing, in psoriasis and in squamous cell carcinomas. Keratinocyte integrins are subject to both transcriptional and post-translational regulation and ligand binding ability can be modulated independently of expression. Studies with cultured keratinocytes suggest a variety of functions for the receptors: adhesion to extracellular matrix proteins, intercellular adhesion, stratification, lateral migration and the regulation of terminal differentiation. Three distinct subpopulations of basal keratinocytes, with characteristics of stem cells, transit amplifying cells and cells committed to differentiate, can be distinguished on the basis of differences in integrin expression and function.