Keratinocyte Transglutaminase: Regulation and Release
Recent improvements in the serial culture of keratinocytes (Rheinwald, 1980; Allen-Hoffman and Rheinwald, 1984) now permit detailed analysis of the differentiation program in this cell type (Green, 1979). To study the program at a molecular level requires identification and characterization of specific marker proteins, regulation of whose synthesis and utilization are important in the cell function. In addition to the high content of keratin (and related cytoskeletal elements), the intracellular transglutaminase is responsible in part for the distinctive structural cohesiveness of mature squames. Thus, a critical feature of terminal differentiation is the formation of an envelope of cross-linked protein immediately beneath the plasma membrane, a transglutaminase-mediated process carried out by keratinocytes in culture (Sun and Green, 1976; Green, 1977; Rice and Green, 1977 and 1978). The cross-linking is elicited by elevation of calcium ion available to the enzyme and results in utilization of involucrin (Rice and Green, 1979; Simon and Green, 1985) and several other protein substrates (Simon and Green, 1984).
KeywordsTerminal Differentiation Human Epidermal Keratinocytes Tissue Transglutaminase Transglutaminase Activity Retinyl Acetate
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