title: Regulation of smooth muscle cell proliferation by beta-catenin/T-cell factor signaling involves modulation of cyclin D1 and p21 expression.
abstract: We previously observed that stimulation of vascular smooth muscle cell (VSMC) proliferation with growth factors is associated with dismantling of cadherin junctions and nuclear translocation of beta-catenin. In this study we demonstrate directly that growth factors stimulate beta-catenin/T-cell factor (TCF) signaling in primary VSMCs. To determine whether beta-catenin/TCF signaling regulates VSMC proliferation via modulation of the beta-catenin/TCF responsive cell cycle genes, cyclin D1 and p21, we inhibited beta-catenin/TCF signaling by adenoviral-mediated over-expression of N-Cadherin, ICAT (an endogenous inhibitor of beta-catenin/TCF signaling), or a dominant negative (dn) mutant of TCF-4. N-cadherin, ICAT or dnTCF-4 over-expression significantly reduced proliferation of isolated human VSMCs by approximately 55%, 80%, and 45% respectively. Similar effects were observed in human saphenous vein medial segments where proliferation was reduced by approximately 55%. Transfection of dnTCF-4 in the ISS10 human VSMC line significantly lowered TCF and cyclin D1 reporter activity but significantly elevated p21 reporter activity, indicating regulation of these genes by beta-catenin/TCF signaling. In support of this, over-expression of N-cadherin, ICAT or dnTCF-4 in isolated human VSMCs significantly lowered levels of cyclin D1 mRNA and protein levels. In contrast, over-expression of N-Cadherin, ICAT or dnTCF4 significantly elevated p21 mRNA and protein levels. In summary, we have demonstrated that increasing N-cadherin and inhibiting beta-catenin/TCF signaling reduces VSMC proliferation, decreases the expression of cyclin D1 and increases levels of the cell cycle inhibitor, p21. We therefore suggest that the N-cadherin and beta-catenin/TCF signaling pathway is a key modulator of VSMC proliferation via regulation of these 2 beta-catenin/TCF responsive genes.
authors.affiliation: Bristol Heart Institute, Level 7, Bristol Royal Infirmary, Upper Maudlin St Bristol, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Quasnichka
authors.forename: Sadie C
authors.initials: SC
authors.lastname: Slater
authors.forename: Cressida A
authors.initials: CA
authors.lastname: Beeching
authors.forename: Manfred
authors.initials: M
authors.lastname: Boehm
authors.forename: Graciela B
authors.initials: GB
authors.lastname: Sala-Newby
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: George
mesh_terms: D001011:Aorta / Q000166:cytology; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000235:genetics* / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D012501:Saphenous Vein / Q000166:cytology; D015398:Signal Transduction / Q000502:physiology; D051820:TCF Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology; D014652:Vascular Diseases / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D051176:beta Catenin / Q000378:metabolism*
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D036341:Intercellular Signaling Peptides and Proteins; D051820:TCF Transcription Factors; D051176:beta Catenin; D019938:Cyclin D1