V. Gahtan et al., Thrombospondin-1 induces activation of focal adhesion kinase in vascular smooth muscle cells, J VASC SURG, 29(6), 1999, pp. 1031-1035
Citations number
22
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Purpose: Vascular smooth muscle cell (VSMC) proliferation and migration are
important events in the development of intimal hyperplasia. Thrombospondin
-1 (TSP-1), an extracellular matrix protein present in intimal hyperplastic
lesions, has been shown to stimulate VSMC proliferation and migration. We
hypothesized that the focal adhesion plaque, specifically the focal adhesio
n kinase (PAK) protein, may be important in the signal transduction pathway
for TSP-1-induced VSMC migration.
Methods: Growth-arrested bovine aortic VSMCs were treated with TSP-1 (20 mu
g/mL) for set intervals (15, 30, and 120 minutes) and compared with VSMCs
grown in serum-free medium (negative control) or in the presence of a known
mitogen and chemotactic factor, platelet-derived growth factor (10 ng/mL;
positive control). Crude cell lysates and anti-PAK immunoprecipitates were
assayed for phosphotyrosine activity by means of antiphosphotyrosine immuno
blotting. The blots were quantified by means of densitometric analysis.
Results: TSP-1 increased tyrosine phosphorylation of three protein bands of
molecular weights 68, 125 (consistent with FAK), and 180 kDa. Immunoprecip
itation with FAK antibody, followed by antiphosphotyrosine immunoblotting,
indicated that there was an increase in tyrosine phosphorylation of FAK at
15, 30, and 120 minutes in the TSP-1-treated groups (P < .05).
Conclusion: Tyrosine phosphorylation of FAK is induced by TSP-1 stimulated
VSMCs. This suggests an outside-inside signaling pathway by which TSP-1 sti
mulates VSMC migration.