[Functional analysis of a novel cell adhesion molecule, gicerin]

Recent studies identified a novel cell adhesion molecule, gicerin, that exists on the surface of developing neurons. Determination of the amino acid sequence revealed that this molecule has five immunoglobulin-like structures in its extracellular domain and a short cytoplasmic tail. Gicerin binds in a homophilic manner and also displays heterophilic binding activity to NOF (Neurite Outgrowth Factor), which belongs to the laminin family extracellular matrix molecule. We clarified that there are two subtypes of gicerin that differ only in the cytoplasmic domain. S-gicerin, which has smaller tail, has stronger activity in cell aggregation or NOF binding. This suggests a physiological difference in the activity of each subtype. In the nervous system, gicerin is expressed during its developmental stage when neurons migrate or extend neurites to form a neural network. Gicerin promotes neurite extension from embryonic neurons by both homophilic adhesion and heterophilic adhesion to NOF. These data suggest that gicerin participates in the formation of neural tissues. Gicerin is also expressed in other tissues such as the kidney and trachea. In these tissues, gicerin expression is also observed during the regeneration process and in tumors in addition to being present during the developmental stage. We believe that gicerin plays an important role in the histogenesis of the nervous system as well as other tissues.