Brain Lectins:Structure and Function.

Although a large variety of carbohydrate-binding proteins are detected in brain tissue, a few number of them have been isolated and their role defined. They include β-galactoside binding lectins, mannose-binding lectins and glycosaminoglycan-binding proteins. These components play different roles during brain ontogenesis. Axonal tracing and/or neurite fasciculation, intracellular trafficking and nuclear function are suspected for the former. The role of mannose-binding lectins has been documented as molecules involved in cell-adhesion or recognition mechanism like contact guidance of migration of immature neurons, myelination and synaptogenesis. Both β-galactoside- and mannoside-binding lectins could be of interest for understanding demyelinating diseases like experimental allergic encephalomyelitis and multiple sclerosis, respectively. A special role of mannose-binding lectins could be postulated in loss of contact inhibition and specific homing of malignant cells.Several carbohydrate-binding proteins have been identified in brain tissue with variable carbohydrate specificities and function. Some of these compounds are involved in general phenomena like, intracellular trafficking and homing of circulating cells and other in specific cell adhesion processes. The cell adhesion concerned with, i) the role of a membrane-bound mannose binding lectin, R1, in neuronal recognition as a first step of synaptogenesis, ii) the role of a soluble mannose-binding protein, CSL, in adhesion processes like stabilization of myelin structure, formation of contact between axons and myelinating cells, contact guidance of neuron migration during development. These molecules are bearing on pathology, for example a β-galactoside-binding lectin is involved in experimental allergic encephalomyelitis and lectin CSL in multiple sclerosis. The glycobiological system of cell adhesion and cell recognition may be of importance in the process of loss of contact inhibition of malignant cells and in their homing mechanism.