THE CYTOPLASMIC DOMAIN OF THE CELL-ADHESION MOLECULE L1 IS NOT REQUIRED FOR HEMOPHILIC ADHESION

L1 is a highly conserved cell adhesion molecule with complete homology of the cytoplasmic domain between the known mammalian protein sequenc es. Since the cytoplasmic domains of other adhesion molecules have bee n shown to influence adhesion, we have investigated the effects of del etion of the cytoplasmic domain on the ability of L1 to mediate hemoph ilic adhesion. Full length L1 and a truncated L1, lacking 95% of the c ytoplasmic domain, were expressed in myeloma cells. Independent stable transfectants were assayed for the ability to form aggregates. Myelom as expressing L1 lacking the cytoplasmic domain were able to form cell aggregates as well as the myelomas expressing full length L1. Cell ag gregate formation was correlated with the level of ii expression, and the aggregation could be blocked by anti-L1 Fabs. Similar results were obtained in adhesion assays of the myeloma cells to substrate-bound L 1. These results indicate that the cytoplasmic domain of L1 is not req uired for hemophilic interactions.