Abstract 367: Beta-catenin C-terminus Signaling Drives Sphingosine-1-phosphate Receptor-1 Expression in Smooth Muscle Cells to Promote Vascular Remodeling

Introduction: Vascular remodeling is associated with target organ damage and fatal cardiovascular events. The molecular mechanisms that control vascular remodeling are still poorly understood, limiting effective therapeutic approaches. The β-catenin C-terminal domain is required in smooth muscle cells (SMCs) for artery formation during embryogenesis, but its role in vascular remodeling in adulthood is unknown. Therefore, the objective of this study was to define the importance of β-catenin C-terminal domain in SMCs during vascular remodeling. Hypothesis: β-catenin C-terminal signaling is required for neointima formation after vascular injury. Methods: We studied male and female mice expressing a C-terminus-deficient β-catenin specific to SMCs (SMβCΔC mice). Mouse aortic SMCs (MASMCs) were isolated from SMβCΔC mice (βCΔC MASMCs). Results are shown as mean ± SEM. Results: SMβCΔC mice show reduced neointima formation (males: WT 100±17 vs SMβCΔC 30±9; females: WT 100±19 vs SMβCΔC 30±7; n=10; P<0.05) and decreased SMC proliferation (males: WT 100±6.8 vs SMβCΔC 22±5.9; females: WT 100±9.9 vs SMβCΔC 34±9.0; n=5; P<0.05) after arterial injury. RNA-seq analysis revealed a downregulation of the sphingosine-1-phosphate receptor 1 (S1pr1) transcript in βCΔC MASMCs. We further found that β-catenin interacts with the S1pr1 promoter (Cut&Run assay, IgG Control 1.00±0.06 vs β-catenin 2.82±0.50; n=4; P<0.05) and acts through its C-terminal domain to activate S1pr1 transcription (luciferase reporter assay, vector Control 100.0±17.08 vs βCΔC 19.9±5.8; n=6; P<0.05) and protein expression (Control 0.95±0.20 vs βCΔC 0.08±0.02; n=4; P<0.05). Consistent with these observations, S1PR1 expression was decreased in SMCs of arteries from SMβCΔC mice (WT 100±6.9 vs SMβCΔC 8±2.1; n=5; P<0.05), and re-establishing SMC S1PR1 expression rescued neointima formation (SMβCΔC 0.15±0.02 vs SMβCΔC;S1PR1Gain-of-function 0.93±0.11; n=8; P<0.05). Conclusion: Our findings identify β-catenin C-terminal output as a novel upstream regulator of S1PR1 expression and define an essential β-catenin/S1PR1 axis that drives neointima formation after injury. Targeting this axis could provide a therapeutic strategy to reduce vascular remodeling and cardiovascular disease.