Abstract 221: PDGF-Mediated Activation of CREB in Vascular Smooth Muscle Cells Alters Cell Cycling via Rb, p27kip1 and Fox01
Introduction: Vascular injury initiates signals which lead to the secretion of humoral factors and ultimately to vessel repair. PDGF is one such factor that promotes conversion of smooth muscle cells (SMC) from their contractile state to the synthetic phenotype, which is characterized by the ability to migrate and proliferate. If not properly controlled, such changes can lead to neointimal hyperplasia or restenosis. As CREB has been shown to participate in vascular remodeling, it is plausible that it is an important player in PDGF-mediated phenotypic switch.
Hypothesis and aim: We assessed the hypothesis that a relationship exists between CREB and PDGF-dependent proliferation of coronary artery SMCs. We also aimed to identify the pathways both upstream and downstream of CREB activation.
Methods: Vascular SMCs from porcine explants and Western blotting were used to monitor protein levels and changes in phosphorylation resulting from various treatments. Multiple cell growth methods were applied to study cell proliferation. A dominant-negative CREB mutant and constitutive expression of p27kip1 were used to assess the involvement of these proteins in mediating the actions of PDGF.
Results: Phosphorylation of CREB by PDGF was dependent on both Src and PI3 kinase, and partially dependent on MAPK. Dominant-negative CREB decreased PDGF-dependent cell proliferation by approximately 75%, and both PCNA expression and Ser-780 phosphorylation of Rb were inhibited. While no change in either cyclin D or cdk4 levels was observed, PCNA and Rb mediate the signals transduced through CREB. These cell cycle proteins likely controlled via p27kip1 expression in response to CREB-dependent Fox01 acetylation.
Conclusion: CREB phosphorylation is required for SMC proliferation in response to PDGF. Additionally, p27kip1 mediates the actions of CREB in SMCs, likely as a result of changes in Fox01 activity.
Author Disclosures: P. Molnar: None. R. Perrault: None. P. Zahradka: None.
- © 2014 by American Heart Association, Inc.