Identification and characterization of binding proteins with gangliosides expressed in the brain and nervous system

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Gangliosides, sialic acid-containing glycosphingolipids, are physiological molecules expressed ubiquitously in animal plasma membranes. The micro heterogeneity of gangliosides is well established in structure, but little is known about their function, although gangliosides are implicated as functional molecules such as cell growth and differentiation, signal transduction, cell adhesion and so on. We recently established an improved method for the generation of monoclonal antibodies by immunizing mice with purified glycosphingolipids. Using the method, we generated and characterized a numberof series of antibodies against glycosphingolipids. There are a number of possible applications of these antibodies not only in basic science butalso in clinical medicine. In this study, we tried to identify and characterize ganglioside binding proteins from brain. In 2000, we identified a GT1b binding protein as brain-specific sodium-dependent inorganic phosphate cotrnasporter (BNPI). Subsequently, we attempted to characterize its binding domain with gangiioside GT1 b, and to identify another binding proteins. Regarding with the first issue, we have not succeeded in the determination yet, probably due tothe fact that BNPI gene-introduced cells can not keep alive. Regarding with the second issue, we detected large molecules associated with GD1a and GD1b, suggesting that they are mucin. At present, we are working on the determination of these molecules. We expect that the analysis of the binding proteins should reveal the functionp of gangliosides in the brain.