engleski

Neuroplastin expression and submembrane distribution is related to specific ganglioside composition

Gangliosides are membrane glycosphingolipids particularly abundant and important for modulating various cellular events in mammalian brain. Ganglioside composition influences appropriate positioning and function of specific membrane proteins, such as neuroplastin (Np) - a transmembrane glycoprotein involved in promoting neurite outgrowth, regulation of structure and function of synapses and synaptic plasticity. Our previous results showed changed Np expression in human hippocampi affected by Alzheimer’s disease (AD). In addition, we reported altered hippocampal Np expression and distribution in mice lacking complex gangliosides. However, positioning of Np within specific membrane subdomains has not been investigated so far. In this study we aimed to analyze Np expression and submembrane distribution in brain tissue of mice with aberrant ganglioside synthesis and mouse model of AD. Cortical tissue was dissected from brains of: APP/PS1 transgenic mice (AD model), B4galnt1 knock-out (KO) and St3gal2/3 double knock-out (DKO) mice with aberrant brain ganglioside composition, and their corresponding wild-type (WT) controls. Membrane proteins were isolated from tissue homogenates and Np expression was analyzed using Western blot followed by ImageJ quantification. Membrane proteins from cortices of KO and DKO mice were additionally segregated in lipid raft and non-raft domains, using procedure for lipid raft isolation modified in our laboratory. Neuroplastin distribution within the specific membrane fractions was analyzed using Western blot and ImageJ quantification. We report altered expression of two major Np isoforms in cortical tissue derived from all mouse models analyzed as compared to WT mice, most prominently in KO mice. Also, we show differences in Np membrane positioning depending on ganglioside composition. Specifically, there is a shift of Np from lipid raft to non-raft domains in cortical tissue of KO and DKO mice compared to WT animals. The results confirm our hypothesis that Np expression and membrane distribution depends on different ganglioside milieu. Observed alteration of Np expression and positioning within membrane is clearly related to documented specific changes in ganglioside quantity and composition in brain tissue of APP/PS1 transgenic mice, as well as mice models with interrupted ganglioside biosynthesis.

Neuroplastin, Gangliosides, Lipid rafts, Neurodegeneration

nije evidentirano