Cellular distribution of the neutral amino acid transporter subtype ASCT2 in mouse brain

Abstract

1These authors contributed equally to this work.Abbreviations used: FBS, fetal bovine serum; GFAP, glial fibrillary acidic protein; MAP-2, microtubule associated protein-2; PFA, paraformaldehyde. AbstractASCT2 is an ASC (alanine-, serine-, cysteine-preferring) neutral amino acid exchanger that may regulate CNS function by transporting amino acid substrates including L-serine, L-cysteine, L-glutamine, L-glutamate and D-serine. Despite the potentially important role of ASCT2 in influencing metabolic and signaling functions of these amino acids in brain, there has been little description of its distribution in brain tissue. We employed a commercially available human ASCT2 antibody in immunohistochemistry studies in adult mouse brain and found a wide regional distribution for ASCT2 that was limited to dendrites labeled by anti-microtubule-associated protein-2 in cortex, hippocampus and striatum. No ASCT2 immunoreactivity was observed in areas labeled by antibodies against a neuronal cell body marker (NeuN), or either of the astrocyte markers, glial fibrillary acidic protein or S100b. In cerebellum both Purkinje cell bodies and dendrites were positive for ASCT2 immunoreactivity. In support of a dendritic localization for ASCT2 in cortex, low affinity (K T > 1 mM), Na + -dependent D-serine and L-glutamine uptake characteristic of ASCT2-mediated transport was observed in P2 synaptosomal preparations. These results suggest that ASCT2 may be an important neuronal neutral amino acid transporter and highlight a discrepancy between findings of astrocyte ASCT2 function in tissue culture and brain in situ.

Defining Substrate and Blocker Activity of Alanine-Serine-Cysteine Transporter 2 (ASCT2) Ligands with Novel Serine Analogs

“…ASCT2 is expressed in many tissues, including the brain, in which it may contribute to glutamine homeostasis of neurons and astrocytes (Bröer and Brookes, 2001;Deitmer et al, 2003;Gliddon et al, 2009). It was hypothesized, for example, that ASCT2 mediates efflux of glutamine from astrocytes, a process that is critical for the functioning of the glutamateglutamine cycle, which recycles synaptically released glutamate.…”

Brain interstitial fluid glutamine homeostasis is controlled by blood–brain barrier SLC7A5/LAT1 amino acid transporter

“…[14][15][16][17] Astrocytes express a wide range of Gln transporters such as SLC1A5 (ASCT2), SCL38A2 (SNAT2), SCL38A3 (SNAT3), SLC38A5 (SNAT5), SLC7A6 (y þ LAT2), SLC7A5 (LAT1) and SLC7A8 (LAT2), 14,[18][19][20][21] although in adults ASCT2 and y þ LAT2 levels are minimal. 18,22 The abundantly expressed Na þ -dependent pH sensitive SNAT3 and SNAT5 are thought to be the main astrocytic transporters for Gln efflux to neurons for the Glu/GABAGln cycle. 7 The BBB also expresses several different AAT involved in Gln transport.…”

“…The data are based on in vivo and in vitro studies. 2,3,[12][13][14][15][16][17][18][19][20][21][22][23]24 AA content was quantified and AA regulation investigated by in vivo microdialysis in freely moving mice.…”

The neurobiology of D-amino acid oxidase and its involvement in schizophrenia

“…[113][114][115] Furthermore, a second D-serine transporter, ASCT2, [116][117][118] believed to be glial, 119 is now also reported to be localized to neurons. 120 These data suggest that a substantial portion of synaptic D-serine is taken up into the neurons, thus indirectly supporting the possibility that DAO is functional in both the neurons and glia. Subcellular localization.…”