engleski

Searching for protein-lipid interactions: ganglioside profiling of neuroplastin knock-out mice

Proper positioning and function of membrane proteins depends on the lipid composition of the plasma membrane as result of lipid-protein interactions. Indeed altered glycosphingolipid environment, e.g. in mice with disrupted ganglioside synthesis, causes change in localisation of membrane proteins, especially lipid raft proteins. We have shown that in mice lacking complex gangliosides, sialic acid-bearing glycosphingolipids especially abundant in mammalian brain, expression of cell adhesion molecule neuroplastin (Np) is increased and distribution altered. Nps are important for brain function: studies on human cognition show that a SNP in the regulatory region of the human Np gene correlates with cortical thickness and cognitive abilities in adolescents. Moreover, mice lacking Np display reduced number and altered function of synapses in the hippocampus. As both Np and gangliosides are important molecular constituents of synaptic membranes and we previously shown that ganglioside composition affects Np localisation, it is of particular interest to determine their specific intermolecular interactions. The aim of this study was to answer the question whether lack of neuroplastin leads to changes in brain ganglioside content and composition. For that purpose, we used brain tissue (cortex, hippocampus and cerebellum) of neuroplastin knock-out (Nptn KO) mice. The gangliosides were extracted, quantified and separated by high performance thin layer chromatography (HPTLC). The overall ganglioside concentration as well as appearance in HPTLC was similar in wild-type (wt) and Nptn KO mice, indicating there is no disturbance in ganglioside composition in animals lacking Np. However, to look for subtle differences in structural diversity of brain gangliosides of wt and Nptn KO mice, we further analysed the extracted gangliosides by tandem mass spectrometry and structurally characterized them in detail. Since the ganglioside environment seems to be, apart from minor modifications, comparable in brain of Nptn KO and wt mice, that indicates that gangliosides influence neuroplastin, both on gene and protein expression level, but not vice versa. That observation is an excellent starting point for clarifying the exact relationship, particularly specific intermolecular interactions between gangliosides and neuroplastin within the membrane.

gangliosides; neuroplastin

nije evidentirano