1. ^*Department of Medicine, Stony Brook University School of Medicine, Stony Brook, New York, USA
2. ^†Department of Dermatology, Stony Brook University School of Medicine, Stony Brook, New York, USA
3. ^‡Veterans Affairs Medical Center at Northport, Northport, New York, USA
4. ^§Department of Pathology, Stony Brook University School of Medicine, Stony Brook, New York, USA

Correspondence: Barry L. Gruber, HSC-16 040, Stony Brook University, Stony Brook, NY 11794-8161, USA. Email: barry.gruber@sunysb.edu

Received 16 November 2003; Revised 8 June 2004; Accepted 11 June 2004; Published online 7 October 2004.

Abstract

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-. 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.