Cadherin-mediated adhesion in pancreatic islet cells is modulated by a cell surface N-acetylgalactosaminylphosphotransferase

Rat pancreatic islet cells and RINm5F cells, an islet derived cell line, have at their cell surface an N-acetylgalactosaminylphosphotransferase (GalNAcPTase) similar to that found at the surface of chick neural retina cells and at the rat neuromuscular junction. On islet cells and RINm5F cells the GalNAcPTase is stably associated with cadherin cell-cell adhesion molecules. The effect of antibodies directed against the GalNAcPTase on homophilic, cadherin mediated adhesion was analyzed by measuring their effect on adhesion of islet and RINm5F cells to an immobilized anti-cadherin antibody. In this experimental paradigm anti-GalNAcPtase antibodies completely inhibit cadherin mediated adhesion. Furthermore, cadherin and GalNAcPTase co-distribute in islet and non-islet tissue. We conclude that pancreatic islet cell-cell adhesion is cadherin mediated and under the control of a tightly associated, cell surface GalNAcPTase.