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Reaction of mast cell proteases tryptase and chymase with protease activated receptors (PARs) on keratinocytes and fibroblasts
Author(s) -
Schechter Norman M.,
Brass Lawrence F.,
Lavker Robert M.,
Jensen Pamela J.
Publication year - 1998
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199808)176:2<365::aid-jcp15>3.0.co;2-2
Subject(s) - tryptase , chymase , proteases , protease activated receptor , thrombin , receptor , mast cell , protease activated receptor 2 , chemistry , trypsin , microbiology and biotechnology , phospholipase c , biochemistry , biology , immunology , enzyme , platelet , enzyme linked receptor
Protease activated receptors (PARs) compose a family of G protein signal transduction receptors activated by proteolysis. In this study, the susceptibility of PARs expressed on human keratinocytes and dermal fibroblasts to the human mast cell proteases tryptase and chymase was evaluated. PAR activation was measured by monitoring cytosolic [Ca 2+ ] in cells loaded with the fluorescent Ca 2+ probe Fura‐2. Tryptase produced transient cytosolic Ca 2+ mobilization in keratinocytes, but not in fibroblasts. Ca 2+ mobilization in keratinocytes required enzymatically active tryptase, demonstrated desensitization, and was blocked by pretreatment of cells with the PAR‐2 peptide agonist SLIGKV, trypsin, or the phospholipase inhibitor U73122. Heparin, a GAG that binds to tryptase, stabilizing its functional form, also inhibited tryptase‐induced Ca 2+ mobilization. The maximal response elicited by tryptase was smaller than that observed upon treatment of keratinocytes with trypsin, a known activator of PAR‐2, and keratinocytes made refractory to tryptase by pretreatment with the protease remained responsive to trypsin. Pretreatment of keratinocytes with thrombin, an activator of PAR‐1 and ‐3 (thrombin receptors), had no detectable effect on the tryptase or trypsin responses. These data suggest that in keratinocytes tryptase may be activating a subpopulation of PAR‐2 receptors. Treatment of keratinocytes or fibroblasts with human chymase did not produce Ca 2+ mobilization, nor did it affect Ca 2+ mobilization produced by trypsin. However, chymase pretreatment of fibroblasts rapidly inhibited the ability of these cells to respond to thrombin. Inhibition was dependent on chymase enzymatic activity and was not significantly affected by the presence of heparin. This finding is consistent with studies indicating that PAR‐1 may be susceptible to proteases with chymotrypsin‐like specificity. These results suggest that the proteases tryptase and chymase secreted from mast cells in skin may affect the behavior of surrounding cells by the hydrolysis of PARs expressed by these cells. J. Cell. Physiol. 176:365–373, 1998. © 1998 Wiley‐Liss, Inc.