GABA transporters in microglial cells.
Gamma-Aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system, has recently been shown to play an inhibitory role in the immune system. GAT-1, the major high-affinity plasma membrane transporter for GABA, is localized widely in neurons (Itouji et al., 1996; Morara et al., 1996; Conti et al., 2004; Fattorini et al., 2017), particularly on axon terminal (E. Siucinska, A. Hamed, M. Jasinska 2014). GAT-1 is also expressed on astrocytes (Vas et al., 2011; Yadav et al., 2015; Ghirardini et al., 2018) as well as on oligodendrocytes (Fattorini et al., 2017). Regarding its expression on microglial cells, the only evidence comes from a work were the authors showed the enhancement of GABAergic transmission, with specific inhibitor of GAT1 (tiagabine), attenuated LPS-mediated microglial activation (Liu et al., 2015). The goal of this project is to verify the expression and function of GATs, particullarly GAT1, on microglial cells and its involvement in neuroinflammation.
We would perform experiments of fluorescence microscopy on CX3CR1+/gfp mice to reveal the presence of GATs positive microglial cells, by taking advantage of GFP expression exclusively on microglia. Then we will analyze size, morphology and phenotype of GATs positive microglia. Finally, we will perform in vitro functional assays to analyze Na+-dependent GABA uptake on microglial cells. Selective GATs inhibitors (NNC-711 for GAT-1 and SNAP-5114 for GAT-2/3) will be used to verify specific involvement of GATs subunits on microglial cells. Moreover, in vitro, we will analyze if pro-inflammatory stimuli could modify the expression of GATs on microglial cells. We will also confirm these data in vivo, on mice treated with LPS.
The results could suggest that microglial cells may contribute to pathophysiology of several neuroinflammatory diseases through the implication of GATs.