Ethanol inhibits neural cell-cell adhesion.

Gestational exposure to ethanol causes defects in neuronal migration, fasciculation, and synaptogenesis, developmental events that depend on the patterned expression and function of cell adhesion molecules (CAMs). Recombinant human osteogenic protein-1 (hOP-1) increases cell-cell adhesion and promotes cell clustering in proliferating neuroblastoma x glioma hybrid NG108-15 cells by strongly inducing N-CAM and L1. Here we show that concentrations of ethanol achieved during social drinking inhibit hOP-1-induced cell clustering without affecting cell proliferation, the induction and cell surface expression of N-CAM and L1, or the alternative splicing and sialylation of N-CAM. This inhibition was reproduced by other alcohols in proportion to their chain length, but not by teratogenic anticonvulsants or phenylalanine. Ethanol inhibition of hOP-1 morphogenesis was inversely proportional to the concentration of hOP-1 and, hence, to the levels of N-CAM and L1. Low concentrations of ethanol (IC50 5-10 mM) inhibited cell-cell adhesion in hOP-1-treated cells, and this action too was reproduced more potently by propanol and butanol. Ethanol may perturb brain and skeletal development by inhibiting CAM-mediated cell-cell interactions.

Regulation of neural cell adhesion molecule and L1 by the transforming growth factor-beta superfamily. Selective effects of the bone morphogenetic proteins.

The transforming growth factor-beta (TGF-beta) superfamily plays a role in embryogenesis and regeneration. We have reported that osteogenic protein-1 (OP-1) promotes cell aggregation and induces the expression of the neural cell adhesion molecules N-CAM and L1 in proliferating neuroblastoma x glioma hybrid NG108-15 cells (Perides, G., Safran, R. M., Rueger, D. C., and Charness, M. E. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 10326-10330; Perides, G., Hu, G., Rueger, D. C., and Charness, M. E. (1993) J. Biol. Chem. 268, 25197-25205). Here we show that the structurally homologous bone morphogenetic proteins (BMP) BMP-2 and BMP-4 are 10-50-fold more potent in these actions than the subfamily comprising BMP-5, BMP-6, and OP-1 (BMP-7). In contrast, members of the TGF-beta subfamily, activin-A, inhibin-A, and 29 additional growth factors and cytokines did not induce N-CAM. The addition of serum to cells growing in serum-free medium caused a concentration-dependent increase in N-CAM and L1 expression; however, serum did not potentiate the induction of N-CAM and L1 by 40 ng/ml OP-1. These findings suggest the presence in NG108-15 cells of a BMP-2/BMP-4 receptor that discriminates subtle differences in structure among homologous members of the TGF-beta superfamily. An endogenous ligand for this receptor may be present in serum.

Induction of the neural cell adhesion molecule and neuronal aggregation by osteogenic protein 1.

The neural cell adhesion molecule (N-CAM) plays a fundamental role in nervous system development and regeneration, yet the regulation of the expression of N-CAM in different brain regions has remained poorly understood. Osteogenic protein 1 (OP-1) is a member of the transforming growth factor beta superfamily that is expressed in the nervous system. Treatment of the neuroblastoma-glioma hybrid cell line NG108-15 for 1-4 days with recombinant human OP-1 (hOP-1) induced alterations in cell shape, formation of epithelioid sheets, and aggregation of cells into multilayered clusters. Immunofluorescence studies and Western blots demonstrated a striking differential induction of the three N-CAM isoforms in hOP-1-treated cells. hOP-1 caused a 6-fold up-regulation of the 140-kDa N-CAM, the isoform showing the highest constitutive expression, and a 29-fold up-regulation of the 180-kDa isoform. The 120-kDa isoform was not detected in control NG108-15 cells but was readily identified in hOP-1-treated cells. Incubation of NG108-15 cells with an antisense N-CAM oligonucleotide reduced the induction of N-CAM by hOP-1 and decreased the formation of multilayered cell aggregates. Anti-N-CAM monoclonal antibodies also diminished the formation of multilayered cell aggregates by hOP-1 and decreased cell-cell adhesion when hOP-1-treated NG108-15 cells were dispersed and replated. Thus, hOP-1 produces morphologic changes in NG108-15 cells, at least in part, by inducing N-CAM. These observations suggest that OP-1 or a homologue may participate in the regulation of N-CAM during nervous system development and regeneration.