Mechanical stretch augments PDGF receptor β expression and protein tyrosine phosphorylation in pulmonary artery tissue and smooth muscle cells

With regard to the mechanotransduction mechanisms of vasculature involved in hypertensive diseases, we aimed to identify tyrosine-phosphorylated proteins in pulmonary artery that responded to mechanical stress. Mechanical stretch simultaneously augmented protein-tyrosine phosphorylation in p55, p95, p105, p115, p130, p165, p180 in pulmonary artery tissue and pulmonary artery-derived smooth muscle cells (PASMC), whereas p115 and p55 were preferentially phosphorylated by the stretch in endothelial cells (PAEC). A series of experiments designed to characterize these proteins indicated that p115 and p180 were focal adhesion kinase (FAK) and platelet-derived growth factor receptor beta (PDGF-R beta), respectively, and that stretch augmented the surface-expression of PDGF-R beta in PASMC but not in PAEC. Moreover, a significant increase in the steady-state mRNA level for PDGF-R beta was observed in the pulmonary artery of rats with monocrotaline-induced pulmonary hypertension, where the artery should be overstretched due to increasing pulmonary arterial blood pressure. These results suggest that stretch-induced overexpression of cell-surface PDGF-R beta as well as augmentation of tyrosine phosphorylation of proteins including FAK in PASMC might be involved in the mechanotransduction of pulmonary artery.