engleski

GM1-containing lipid rafts are housing neuroplastin in neuronal plasma membrane

Gangliosides and the cell adhesion molecule neuroplastin (Np) are abundant constituents of neuronal plasma membranes and important for brain functions as evidenced in studies from knock-out animals. We demonstrated that hippocampal expression of Np is affected in two transgenic mouse strains each of them with specific alterations in ganglioside composition. Additionally, we observed that Np distribution in membrane sub-domains depends on the ganglioside environment. Here, we aim to visualize the molecular relationship of gangliosides and Np in rat hippocampal neurons during different maturation stages in vitro (6-42 DIV). For that purpose, we performed live cell staining using primary antibodies to identify the two Np isoforms (Np65 and Np55) and the four major brain ganglioside species (GM1, GD1a, GD1b and GT1b) in hippocampal neurons. Co-localization of Np with each of the four gangliosides was analyzed by confocal microscopy. Although all four main brain gangliosides were unequivocally detected in the cell surface of mature hippocampal neurons (≥21DIV), both Np isoforms co-localized predominately with GM1 and only to a much lesser extent with GD1a. Neuroplastin and the four ganglioside species are expressed but do not co- localize in immature neurons (≤12DIV). Our results not only corroborate that the Nps distribute preferentially into isolated GM1- containing lipid rafts but also they suggest that neuroplastin is tightly and largely localized in selective GM1 nanodomains in intact plasma membrane of mature neurons. Therefore, we propose that some of the main functions of Np in mature neurons may be defined by its positioning within a GM1-enriched membrane milieu.

neuroplastin ; gangliosides ; GM1 ; lipid rafts

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