THE RETINA CELL-SURFACE N-ACETYLGALACTOSAMINYLPHOSPHOTRANSFERASE IS ANCHORED BY A GLYCOPHOSPHATIDYLINOSITOL

A polypeptide with N-acetylgalactosaminylphosphotransferase (GalNAcPTase) activity is present at the cell surface in stable association with adhesion molecules of the cadherin family. Antibodies directed against the GalNAcPTase inhibit homophilic cadherin-mediated adhesion and cadherin-mediated neurite outgrowth. We have determined that the GalNAcPTase is anchored at the cell surface by a glycophosphatidylinositol linkage. Treatment of intact cells with phosphatidylinositol-specific phospholipase C (PI-PLC) releases active GalNAcPTase and abolishes the ability of anti-GalNAcPTAse antibodies to modulate cadherin-mediated adhesion or neurite outgrowth. Furthermore, GalNAcPTase released from cells by PI-PLC is recognized by anti-CRD antiserum and is radiolabeled in cells incubated with [C-14]-ethanolamine.