Plasma Membrane Calcium ATPase-Neuroplastin Complexes Are Selectively Stabilized in GM1-Containing Lipid Rafts

Abstract

The recent identification of plasma membrane (Ca2+)-ATPase (PMCA)-Neuroplastin (Np) complexes has renewed attention on cell regulation of cytosolic calcium extrusion, which is of particular relevance in neurons. Here, we tested the hypothesis that PMCA-Neuroplastin complexes exist in specific ganglioside-containing rafts, which could affect calcium homeostasis. We analyzed the abundance of all four PMCA paralogs (PMCA1-4) and Neuroplastin isoforms (Np65 and Np55) in lipid rafts and bulk membrane fractions from GM2/GD2 synthase-deficient mouse brains. In these fractions, we found altered distribution of Np65/Np55 and selected PMCA isoforms, namely PMCA1 and 2. Cell surface staining and confocal microscopy identified GM1 as the main complex ganglioside co-localizing with Neuroplastin in cultured hippocampal neurons. Furthermore, blocking GM1 with a specific antibody resulted in delayed calcium restoration of electrically evoked calcium transients in the soma of hippocampal neurons. The content and composition of all ganglioside species were unchanged in Neuroplastin-deficient mouse brains. Therefore, we conclude that altered composition or disorganization of ganglioside-containing rafts results in changed regulation of calcium signals in neurons. We propose that GM1 could be a key sphingolipid for ensuring proper location of the PMCA-Neuroplastin complexes into rafts in order to participate in the regulation of neuronal calcium homeostasis.

EFR3A: a new raft domain organizing protein?

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Gangliosidome of a Human Hippocampus in Temporal Lobe Epilepsy Resolved by High-Resolution Tandem Mass Spectrometry

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Plasma membrane Ca2+ pump isoform 4 function in cell migration and cancer metastasis

“…While the first PMCA was discovered a long time ago (Schatzmann, 1966), it was only recently found that the glycoproteins neuroplastin (NPTN) and basigin (BSG/CD147/EMMPRIN) can serve as subunits for PMCAs, and that they are essential for their plasma membrane localization and activity in a tissue-specific manner (Gong et al, 2018;Korthals et al, 2017;Schmidt et al, 2017). For example, in neurons the interaction of PMCA1 and PMCA2 with NPTNs NP55 and NP65 supports proper localization of these pumps into GM1 ganglioside-enriched lipid rafts (Ilic, Lin et al, 2021). NPTN controls PMCA expression in postsynaptic neurons, inner ear hair cells and T cells, and the NPTN-PMCA complex plays a crucial role in the regulation of synaptic plasticity, hearing and T cell activation Korthals et al, 2017;Lin et al, 2021;Malci et al, 2022).…”