| Abstrakt: |
Keratinocytes synthesize and secrete urokinase-type plasminogen activator (uPA), which is bound in an autocrine manner to a specific receptor (uPA-R, CD87) at their surface. Plasminogen, which is also bound to membrane binding sites, is readily activated by uPA-R-bound uPA. Thus, plasmin for proteolysis of pericullular glycoproteins is provided. While uPA-R and uPA are at low to undetectable levels in keratinocytes of the normal epidermis, both compounds are upregulated in migrating keratinocytes during reepithelialization of epidermal defects and in affected keratinocytes of various epidermal disorders, including bullous dermatoses. We have hypothesized that the disturbance of cell/matrix interactions—a common feature of these diverse pathological situations—induces uPA/uPA-R. Accordingly, we explored whether the dispase-mediated detachment of cultured keratinocytes, which have formed a multilayered epidermis-like structurein vitro,induced uPA and uPA-R. We found increases in uPA secretion, cell-associated uPA activity, and uPA- and uPA-R-antigen in keratinocytes upon dispase-mediated detachment from their growth substratum. The increase was preceded by an increase in uPA-R- and uPA-specific mRNA, which was not observed when the proteinase inhibitor phosphoramidon was added together with dispase. In conclusion, we present evidence that experimental detachment with dispase provides signals for the concomitant upregulation of uPA-R and uPA. The findings support the hypothesis that cell/matrix interactions may influence the expression of the cell surface-associated PA system in human keratinocytes. |
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