The nervous system specific protein D2 is involved in adhesion among neurites from cultured rat ganglia.

The rat nervous system specific protein D2 is an integral membrane protein present on all bodies and neurites of cultured neurons from brain fetuses [l-3]. In adult brain, D2 is found mainly on the outside of synaptic membranes [4-61. It has been hypothesized that this protein may be involved in the recognition mechanism during the early stage of synaptogenesis 15451. Here we have examined the effect of anti-D2 antibodies on the formation of neurite fascicles from cultured rat sympathetic ganglia. The results indicated that D2 may be involved in neurite-neurite interaction, a property which has been reported for the cell adhesion molecule (CAM) isolated from chick embryo neural tissue [7,8]. This property and similarities in molecular weight, membrane distribution and localization raise the possibility that D2 and CAM may be evolutionarily related proteins. This hypothesis is strengthened by the finding, that anti-CAM antibodies crossreact with D2 protein.