The glycosphingolipid hydrolases in the central nervous system.

Glycosphingolipids are a large group of complex lipids particularly abundant in the outer layer of the neuronal plasma membranes. Qualitative and quantitative changes in glycosphingolipids have been reported along neuronal differentiation and aging. Their half-life is short in the nervous system and their membrane composition and content are the result of a complex network of metabolic pathways involving both the de novo synthesis in the Golgi apparatus and the lysosomal catabolism. In particular, most of the enzymes of glycosphingolipid biosynthesis and catabolism have been found also at the plasma membrane level. Their action could be responsible for the fine tuning of the plasma membrane glycosphingolipid composition allowing the formation of highly specialized membrane areas, such as the synapses and the axonal growth cones. While the correlation between the changes of GSL pattern and the modulation of the expression/activity of different glycosyltransferases during the neuronal differentiation has been widely discussed, the role of the glycohydrolytic enzymes in this process is still little explored. For this reason, in the present review, we focus on the main glycolipid catabolic enzymes β-hexosaminidases, sialidases, β-galactosidases, and β-glucocerebrosidases in the process of the neuronal differentiation.