Differentiation and shedding of surface macromolecules of human keratinocytes.

Macromolecules expressed on the external surface of human keratinocytes in tissue culture were radioiodinated by the lactoperoxidase technique and solubilized by lysing the cells in nonionic detergent. Soluble labeled proteins were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pattern of proteins expressed by keratinocytes was distinct for these cells. The major labeled components had Mrs of 28K, 40K, 68K, 72K, and 77K. The expression of several macromolecules changed with the length of time the cells were in culture, suggesting that their expression was linked to epidermal differentiation. Lastly, many but not all of the macromolecules expressed on the surface of keratinocytes were selectively and rapidly released into medium by the cells.