N-Cadherin andβ-Catenin involvement in BMP-2 induction of mesenchymal chondrogenesis

Abstract

Controlled upregulation of N-cadherin expression and function has been shown to be essential for bone morphogenetic protein-2 (BMP-2)-induced chondrogenic differentiation of high-density micromass cultures of the murine multipotential mesenchymal cell line, C3H10T1/2. In this report, we have examined the nature of the N-cadherin-related mechanisms involved in BMP-2-mediated chondrogenesis. BMP-2 treatment altered the expression of catenins, the cytoplasmic components of the adherens junction, and their interactions with N-cadherin. Within 24 h of BMP-2 treatment, immunoprecipitation analysis showed that the association of catenins with N-cadherin was significantly lower. With long-term (9 and 13 days) BMP-2 treatment, β-catenin accumulated in a nuclear localization, with reduced association with the adenomatous polyposis tumor suppressor protein (APC), a factor known to direct β-catenin degradation via ubiquitination. The functional importance of N-cadherin-β-catenin interaction was further investigated by the effect of transfection-mediated over-expression of two forms of β-catenin: wild-type β-catenin inhibited, while an amino terminal truncated (adhesive deficient) β-catenin enhanced BMP-2-induced chondrogenesis. These data indicate that BMP-2 induction of chondrogenesis in the mesenchymal cell line C3H10T1/2 depends on functional alterations in specific cell adhesion and signaling pathways involving N-cadherin-catenin interaction.