Cytoplasmic domain is not essential for the cell adhesion activities of gicerin, an Ig-superfamily molecule

Gicerin is a cell adhesion molecule in the immunoglobulin (Ig) superfamily and is expressed abundantly during development in the nervous system. It ha s homophilic cell adhesion activity and also has heterophilic binding activ ity with NOF (neurite outgrowth factor) and mediates neurite extension. The re are two isoforms of gicerin, one with a short (s-gicerin) and the other with a longer cytoplasmic domain (l-gicerin). We have reported that s-gicer in possesses stronger activities than l-gicerin during cell aggregation, in NOF-binding, and in neurite extension. In this study, we established cell lines which expressed a mutant-gicerin whose cytoplasmic domain was deleted and we compared the above three biological activities of the mutant-giceri n with those of s- and l-gicerin. We found that the mutant-gicerin retained all these activities, but the activities were weaker than those of s-gicer in and almost the same as those of l-gicerin, We concluded that the cytopla smic domain of gicerin is not essential for optimal adhesive activities of gicerin, but might be involved in the regulation of its activities. (C) 199 9 Academic Press.