Protease-activated receptor-2 (PAR-2) expression in human fibroblasts is regulated by growth factors and extracellular matrix.
Many cell types express a membrane receptor, activated by trypsin-like proteases, termed protease-activated receptor-2 (PAR-2). Previous studies describing PAR-2 expression on fibroblasts have been conflicting. In this report, we investigated in vitro PAR-2 expression on several fibroblast cell lines using flow cytometry, immunohistology, and immunoblots of cell lysates. Consistent PAR-2 expression was detected in cultured fibroblasts, although we observed heterogeneity of cellular expression among the cell lines. Some fibroblast lines expressed PAR-2 predominantly as an intracellular protein with differing cytoplasmic staining patterns, whereas other fibroblast lines displayed PAR-2 primarily as a cell surface receptor. Immunoblots of cell lysates with polyclonal anti-PAR-2 demonstrated a 44 kDa band, the predicted molecular weight for the PAR-2 core protein. Furthermore, we noted that expression of PAR-2 was subject to regulation. Fibroblasts grown within a collagen matrix downregulated receptor expression whereas increased PAR-2 expression was observed by the addition of fibroblast growth factors PDGF-BB and TGF-beta. This study may explain the previous inconsistencies in PAR-2 expression observed on tissue fibroblasts. Results indicate that the degree of fibroblast proliferation, attenuated by extracellular matrix and upregulated by growth factors, influences whether fibroblasts express PAR-2 and, thus, would be responsive to protease signaling.
Gruber
Barry L
BL
Department of Medicine, Stony Brook University School of Medicine, Stony Brook, New York, USA. barry.gruber@sunysb.edu
Marchese
Mary J
MJ
Santiago-Schwarz
Frances
F
Martin
Carla A
CA
Zhang
Jianhua
J
Kew
Richard R
RR
D000077214:Becaplermin; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000502:physiology*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015151:Immunoblotting; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis; D044464:Receptor, PAR-2 / Q000235:genetics* / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D044464:Receptor, PAR-2; D016212:Transforming Growth Factor beta; D000077214:Becaplermin