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1 UCSD School of Medicine and Veterans Administration Healthcare San Diego
2 National Heart, Lung, and Blood Institute, NIH
* To whom correspondence should be addressed. E-mail: rross{at}ucsd.edu.
Migration and proliferation of cardiac fibroblasts (CFs) play an important role in the myocardial remodeling process. While many factors have been identified that regulate CF growth and migration, less is known about the signaling mechanisms involved in these processes. Here, we utilized Cre-LoxP technology to obtain Focal Adhesion Kinase (FAK)-deficient adult mouse CFs and studied how FAK functioned in modulating cell adhesion, proliferation and migration of these cells. Treatment of FAKflox/flox CFs with Adeno/Cre virus caused over 70% reduction of FAK protein levels within a cell population. FAK deficient CFs showed no changes in focal adhesions, cell morphology or protein expression levels of vinculin, talin or paxillin; Proline-rich tyrosine kinase 2 (Pyk2) expression and activity were increased. Knockdown of FAK protein in CFs increased PDGF-BB induced proliferation while it reduced PDGF-BB-induced migration. Adhesion to fibronectin was not altered. To distinguish between the function of FAK and Pyk2, FAK function was inhibited via adenoviral-mediated overexpression of the natural FAK inhibitor FAK-Related Non-Kinase (FRNK). Adeno/FRNK had no effect on Pyk2 expression, inhibited the PDGF-BB-induced migration but did not change the PDGF BB-induced proliferation. FAK deficiency had only modest effects on increasing PDGF-BB activation of p38 and JNK MAPKs, with no alteration in the ERK response vs. control cells. These results demonstrate that FAK is required for the PDGF-BB induced migratory response of adult mouse CFs and suggest that FAK could play an essential role in the wound healing response which occurs in numerous cardiac pathologies.
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