Identification of Secreted Proteins during Protease-Activated Receptor 2 Activation in Gastrointestinal Smooth Muscle Cells

Protease-activated receptor 2 is a member of G protein-coupled receptor and expressed in a wide variety of cells. PAR2 is involved in several physiological and pathophysiological processes, including growth and development, inflammation, migration, and apoptosis depending on cell types. However, the role of PAR2 in the context of secretory function of inflammatory proteins in smooth muscle cells remains unknown. The aim of the present study was to determine the secretory proteins involved in inflammatory process upon PAR2 activation in smooth muscle cells. Gastric smooth muscle cells were left untreated or treated with PAR2 activating peptide (PAR2-AP) SLIGKV (1 μM) for up to 48 hours in serum-free medium. Untreated media were used as negative controls. Secretome were collected at 48 hours and subjected to proteomic analysis by LC-MS/MS. A total of 310 peptides were detected and found to correspond to 275 proteins. This approach identified 160 significant changes in protein levels. These proteins were expressed at significantly different levels in treated sample as compared with untreated sample. These proteins could be classified by their functions in inflammation, proliferation and apoptosis, and response to stress. It resulted in the first LC-MS/MS based secretome profiles of gastrointestinal smooth muscle cells. Such secretory protein may be of pathological significance in the role of PAR2 in regulating the inflammation, proliferation, and apoptotic process and may offer protection of cells against physiological stress.