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J Biol Chem. 2018 Feb 23;293(8):2877-2887. doi: 10.1074/jbc.RA117.001342. Epub 2018 Jan 11.

The glutamine transporter ASCT2 (SLC1A5) promotes tumor growth independently of the amino acid transporter LAT1 (SLC7A5).

Author information

1
From the Medical Biology Department, Centre Scientifique de Monaco (CSM), MC 98000 Monaco.
2
J-Pharma, Co. Ltd., Yokohama 230-0046, Japan.
3
School of Pharmacy, Anschutz Medical Campus, University of Colorado Denver, Aurora, Colorado 80045.
4
From the Medical Biology Department, Centre Scientifique de Monaco (CSM), MC 98000 Monaco, sparks@centrescientifique.mc.
5
From the Medical Biology Department, Centre Scientifique de Monaco (CSM), MC 98000 Monaco, jpouyssegur@centrescientifique.mc pouysseg@unice.fr.
6
Institute for Research on Cancer and Aging (IRCAN), CNRS, INSERM, Centre A. Lacassagne, University of Nice Sophia Antipolis, 06088 Nice, France.

Abstract

The transporters for glutamine and essential amino acids, ASCT2 (solute carrier family 1 member 5, SLC1A5) and LAT1 (solute carrier family 7 member 5, SLC7A5), respectively, are overexpressed in aggressive cancers and have been identified as cancer-promoting targets. Moreover, previous work has suggested that glutamine influx via ASCT2 triggers essential amino acids entry via the LAT1 exchanger, thus activating mechanistic target of rapamycin complex 1 (mTORC1) and stimulating growth. Here, to further investigate whether these two transporters are functionally coupled, we compared the respective knockout (KO) of either LAT1 or ASCT2 in colon (LS174T) and lung (A549) adenocarcinoma cell lines. Although ASCT2KO significantly reduced glutamine import (>60% reduction), no impact on leucine uptake was observed in both cell lines. Although an in vitro growth-reduction phenotype was observed in A549-ASCT2KO cells only, we found that genetic disruption of ASCT2 strongly decreased tumor growth in both cell lines. However, in sharp contrast to LAT1KO cells, ASCT2KO cells displayed no amino acid (AA) stress response (GCN2/EIF2a/ATF4) or altered mTORC1 activity (S6K1/S6). We therefore conclude that ASCT2KO reduces tumor growth by limiting AA import, but that this effect is independent of LAT1 activity. These data were further supported by in vitro cell proliferation experiments performed in the absence of glutamine. Together these results confirm and extend ASCT2's pro-tumoral role and indicate that the proposed functional coupling model of ASCT2 and LAT1 is not universal across different cancer types.

KEYWORDS:

ASCT2; LAT1; amino acid; amino acid transport; cancer; cell metabolism; mammalian target of rapamycin (mTOR)

PMID:
29326164
PMCID:
PMC5827425
DOI:
10.1074/jbc.RA117.001342
[Indexed for MEDLINE]
Free PMC Article

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