The organization of adherens junctions in mouse osteoblast-like cells (MC3T3-E1) and their modulation by triiodothyronine and 1,25-dihydroxyvitamin D3

Cadherin-mediated cell-cell adhesion is essential for the development and s urvival of multicellular tissues. Thus it is hypothesized that these molecu les also play a fundamental role for the development and maintenance of bon e by mediating cellular crosstalk between osteogenic cells and by providing targets for the sorting and migration of osteogenic precursors toward the bone surface. We describe the localization of cadherin-11 and N-cadherin al ong the cell margins of mouse osteoblastlike cells, the colocalization of " pancadherin" with acatenin, beta-catenin, p120, and vinculin, and the assoc iation of these complexes with the actin microfilaments. Furthermore, we me asured the influence of cell confluency and the effects of the osteogenic h ormones triiodothyronine (T3) and 1,25-dihydroxyvitamin D3 (D3) on these pa rameters. By mRNA studies we found the abundantly expressed cadherin-11 bei ng unaffected during T3- and D3-induced osteoblastic differentiation. Howev er, protein levels of N-cadherin and "pancadherin" were strongly suppressed by D3. We also observed a clear distinction in cadherin immunolocalization when comparing confluent control and confluent hormone-treated cultures. I mmunoprecipitation experiments indicated that vinculin is part of the junct ional complex, and that the association of "pancadherin"/beta-catenin is st rongly increased after treatment with T3 which might influence the function al competence of cell-cell contacts. Thus, this study demonstrates the mole cular organization of adherens junctions in mouse osteoblastic MC3T3-E1 cel ls and their sensitivity to the osteogenic factors T3 and D3 in confluent c ultures.