E-CADHERINS IDENTIFIED IN OSTEOBLASTIC CELLS - EFFECTS OF PARATHYROID-HORMONE AND EXTRACELLULAR CALCIUM ON LOCALIZATION

The presence and regulation of cadherin localization in osteoblastic c ells were examined. Monoclonal antibody (ECCD-1) that interferes with E-cadherin function prevented cell adhesion in UMR 106-H5 rat osteosar coma cells and non-tumorigenic mouse calvarial MC3T3-E1 cells, whereas CCL39 fibroblast adhesion was not affected. Immunofluorescent antibod ies (ECCD-2 and polyclonal L-CAM Fl) revealed cadherins are localized along the osteoblastic cell-cell boundaries. Exposure of UMR 106-H5 ce lls to bovine parathyroid hormone (1-84) (PTH; 10 ng/ml x 1 hr) or low calcium medium (1.0 0.025 mM) produced cellular retraction accompanie d by intense immunofluorescence for cadherins throughout cells with a corresponding loss of punctate localization at remaining cell-cell adh esion points. Western immunoblot analysis indicated 108 kd and 115 kd cadherins are present, with a smaller 29.5 kd band that became predomi nantly associated with the cytosolic fraction of cells treated with pa rathyroid hormone or lowered calcium. The results demonstrate E-like c adherins are present in osteoblastic cells and implicate a regulatory role for parathyroid hormone and calcium in cadherin function and loca lization.