Cell motility proceeds by cycles of edge protrusion, adhesion and retraction. 
Whether these functions are coordinated by biochemical or biomechanical 
processes is unknown. Tumor invasion and metastasis is directly related to cell 
motility. We showed that stimulation of proteinase-activated receptor-1 (PAR1) 
can trigger an array of responses that would promote tumor cell growth and 
invasion. Thus, we examined aspects of PAR1 activation related to cell 
morphological change that might contribute to cell motility. We established a 
PAR1 stably transfected MKN45 gastric cancer cell line (MKN45/PAR1). We examined 
morphological changes, Rho family activation and overexpression of cytoskeletal 
protein in cells exposed to PAR1 agonists (α-thrombin and TFLLR-NH2). MKN45/PAR1 
grows with an elongated and polarized morphology, extending pseudopodia at the 
leading edge. However, in the presence of PAR1 antagonist, MKN45/PAR1 did not 
show any changes in cell shape upon addition of either α-thrombin or TFLLR-NH2. 
Activated PAR1 induced RhoA and Rac1 phosphorylation, and subsequent 
overexpression of myosin IIA and filamin B which are stress fiber components 
that were identified by PMF analysis of peptide mass data obtained by 
MALDI-TOF/MS measurement. Upon stimulation of MKN45/PAR1 for 24 h with either 
α-thrombin or TFLLR-NH2, the distribution of both myosin IIA and filamin B 
proteins shifted to being distributed throughout the cytoplasm to the membrane, 
with more intense luminescence signals than in the absence of stimulation. These 
results demonstrate that PAR1 activation induces cell morphological change 
associated with cell motility via Rho family activation and cytoskeletal protein 
overexpression, and has a critical role in gastric cancer cell invasion and 
metastasis.