Evidence for intracellular cleavage of plasminogen activator inhibitor type 2 (PAI-2) in normal epidermal keratinocytes

Barbara C. Risse, Nancy M. Chung, Mark S. Baker, Pamela J. Jensen*

*Corresponding author for this work

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Plasminogen activator inhibitor type 2 (PAI-2) is a serine proteinase inhibitor (serpin), present in high quantities in stratified squamous epithelia. Detergent extracts of human epidermis or cultured keratinocytes contain primarily active, nonglycosylated PAI-2. In keratinocytes, the vast majority of PAI-2 is retained within the cell, supporting the hypothesis that PAI-2 may serve specific intracellular function(s) through interaction with an unknown cytoplasmic proteinase. During interaction with the target proteinase, cleavage of PAI-2 within its reactive site loop leads to the formation of a more stable, 'relaxed' conformation (PAI-2r). Using a monoclonal antibody specific for PAI-2r, we demonstrate here that PAI-2r is present in keratinocytes of the granular and basal layers of normal human epidermis. In addition, PAI-2r is detectable in cultured human epidermal keratinocytes, where it is concentrated in a detergent-insoluble fraction within differentiating cells. These data provide evidence for the presence of an endogenous, keratinocyte-derived proteinase that constitutively cleaves intracellular PAI-2 in normal human epidermal keratinocytes. Cleavage of PAI- 2 by this proteinase may reflect specific intracellular action of PAI-2 in norma cells. Finally, we demonstrate that a commercially available anti-PAI-2 monoclonal antibody (3750, American Diagnostica, Greenwich, CT), under native experimental conditions, preferentially recognizes the uncleaved, active form of PAI-2 and does not efficiently detect PAI-2r.

Original languageEnglish
Pages (from-to)281-289
Number of pages9
JournalJournal of Cellular Physiology
Volume182
Issue number2
DOIs
Publication statusPublished - 2000
Externally publishedYes

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