Abstract 15989: The Actin-Binding Protein Drebrin Reduces TRP Channel Activity and Neointimal Hyperplasia
Integral to the pathogenesis of atherosclerosis, vascular smooth muscle cell (SMC) migration and proliferation are regulated by transient receptor potential (TRP) channels: a family of nonselective cation channels shown to modulate calcium influx during vascular remodeling. We have previously shown that proper function of TRP channels requires the scaffolding protein Homer 1, which we found associates with the actin-binding protein Drebrin in yeast two-hybrid and in vitro binding studies. We therefore tested the hypothesis that Drebrin inhibits SMC transformation to the proliferative/migratory phenotype through regulation of TRP channel function. We found that Drebrin expression is upregulated in response to arterial injury, suggesting a role for Drebrin in the regulation of vascular remodeling. We created Drebrin KO (Dbn-/-) mice using β-galactosidase gene-trapped ES cells from the NIH Knockout Mouse Project. Dbn-/- mice showed neonatal mortality, but Dbn-/+ mice appeared equivalent to WT littermates by weight and appearance. The trapping cassette allowed for expression of β-galactosidase under the control of the endogenous Drebrin promoter. As expected, β-galactosidase staining of tissues from Dbn-/+ mice revealed the highest expression levels in the brain, but surprisingly this was followed closely by SMC expression. Dbn-/+ SMCs expressed 50±10% as much Drebrin protein as congenic WT SMCs, showed 56±2% more PDGF-evoked migration in Boyden chamber assays (p<0.05), and an 80±15% increase basal TRP channel activity (p<0.05), assessed as inward current density by the whole cell patch-clamp technique. To determine the effect of Drebrin on SMC migration and proliferation in vivo, WT and congenic Dbn-/+ mice were subjected to wire-mediated carotid endothelial denudation, using a procedure we showed by GFP+ bone marrow transplantation produces neointima arising only from medial SMCs. Dbn-/+ mice exhibited 2.6±0.3-fold more neointimal area than WT: 3.9±0.4 vs. 1.5±0.3 × 104 μm2 (n=5-8/group, p<0.01). We conclude that Drebrin reduces TRP channel activity, and thereby reduces SMC activation/migration, both in vitro and in vivo.
- © 2012 by American Heart Association, Inc.