title: SNAT2 transceptor signalling via mTOR: a role in cell growth and proliferation?
abstract: We have investigated the effect of chronic competitive inhibition of SNAT2 (System A) amino acid (AA) transport, induced by incubation with a saturating dose of a non-metabolisable System A amino acid analogue (Me-AIB), on growth and proliferation of MCF-7 human breast cancer cells in complete culture medium. These cells express Na+- and pH-dependent SNAT2 AA transport and a saturating concentration of Me-AIB (10 mM) competitively inhibits (>90%) AA uptake via SNAT2. Incubation with Me-AIB for up to 5 days progressively reduced cell proliferation (~2-fold) and depleted intracellular concentrations of not only SNAT2 AA substrates but of essential branched chain AAs (e.g. leucine). Surprisingly, total cellular protein was maintained and cells subjected to chronic Me-AIB incubation exhibited a detectable increase in cell size. Analysis of mTOR signalling revealed that, despite a substantial reduction in size of the intracellular AA pool, Me-AIB elevated mTOR-dependent p70S6K1 phosphorylation. Proteomic analysis of TAP-tag purified SNAT2 fusion proteins identified two novel SNAT2-interacting proteins that may potentially function in conjunction with the SNAT2 transceptor to regulate signalling pathways influencing protein turnover and cell growth.
authors.affiliation: Division of Molecular Physiology, James Black Centre, College of Life Sciences, University of Dundee, Dundee, United Kingdom.
authors.forename: Jorge
authors.initials: J
authors.lastname: Pinilla
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Aledo
authors.forename: Emma
authors.initials: E
authors.lastname: Cwiklinski
authors.forename: Russell
authors.initials: R
authors.lastname: Hyde
authors.forename: Peter M
authors.initials: PM
authors.lastname: Taylor
authors.forename: Harinder S
authors.initials: HS
authors.lastname: Hundal
mesh_terms: D026924:Amino Acid Transport System A / Q000378:metabolism*; D015153:Blotting, Western; D002455:Cell Division; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D015398:Signal Transduction
chemical_list: D026924:Amino Acid Transport System A; C498797:SLC38A2 protein, human