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Rho and basic fibroblast growth factor involvement in centrosome redistribution and actin microfilament remodeling
Tsu-Yee Joseph Lee1, Avrum I Gotlieb
1Vascular Research Laboratory, The Toronto General Hospital and Research Institute, 200 Elizabeth Street, Toronto, Ontario, Canada M5G 2C4.
Objective:
We have shown that centrosome redistribution to the front of the cell and actin microfilament remodeling occurs during the initiation of early porcine aortic endothelial wound repair even before cell migration. Because Ras homologous protein (Rho) induces actin microfilament polymerization, interacts with microtubules, and is believed to be activated by growth factors, we set forth to study the regulatory roles of basic fibroblast growth factor (bFGF) and Rho signaling on centrosome redistribution and actin microfilament remodeling in endothelial cells at an in vitro wound edge.
Study Design:
With double immunofluorescent confocal microscopy, we studied the distribution of various cytoskeletal proteins in wounded porcine aortic endothelial cells in response to bFGF and exoenzyme C3 treatments.
Results:
We showed that the addition of 10 ng/mL bFGF for 3 hours after wounding resulted in a significant increase (P <.05) in cells at the wound edge with central microfilaments oriented perpendicular to the wound. Rho inhibition with 2 microg/mL C3 resulted in the reduction of phosphotyrosine, paxillin, and central microfilament staining. Centrosome redistribution and endothelial cell elongation also were significantly inhibited (P <.05) with C3, resulting in decreased wound closure. However, inhibition was reduced with coincubation of bFGF with C3, which also returned the rate of endothelial wound closure toward control values. This Rho-independent bFGF-induced centrosome redistribution was associated with the cells showing a significant increase (P <.05) in acetylated microtubules that extended from the centrosome to the posterior cell border.
Conclusion:
We conclude that Rho regulates centrosome redistribution and central microfilament remodeling during early endothelial wound repair, and bFGF promotes actin remodeling through a downstream Rho-dependent pathway and promotes centrosome redistribution, at least in part, with a Rho-independent pathway.