Insulin increases mRNA abundance of the amino acid transporter SLC7A5/LAT1 via an mTORC1-dependent mechanism in skeletal muscle cells

Dillon K. Walker, Micah J. Drummond, Jared Dickinson, Michael S. Borack, Kristofer Jennings, Elena Volpi, Blake B. Rasmussen

    Research output: Contribution to journalArticle

    19 Scopus citations

    Abstract

    Amino acid transporters (AATs) provide a link between amino acid availability and mammalian/mechanistic target of rapamycin complex 1 (mTORC1) activation although the direct relationship remains unclear. Previous studies in various cell types have used high insulin concentrations to determine the role of insulin on mTORC1 signaling and AAT mRNA abundance. However, this approach may limit applicability to human physiology. Therefore, we sought to determine the effect of insulin on mTORC1 signaling and whether lower insulin concentrations stimulate AAT mRNA abundance in muscle cells. We hypothesized that lower insulin concentrations would increase mRNA abundance of select AAT via an mTORC1-dependent mechanism in C2C12 myotubes. Insulin (0.5 nmol/L) significantly increased phosphorylation of the mTORC1 downstream effectors p70 ribosomal protein S6 kinase 1 (S6K1) and ribosomal protein S6 (S6). A low rapamycin dose (2.5 nmol/L) significantly reduced the insulin-(0.5 nmol/L) stimulated S6K1 and S6 phosphorylation. A high rapamycin dose (50 nmol/L) further reduced the insulin-(0.5 nmol/L) stimulated phosphorylation of S6K1 and S6. Insulin (0.5 nmol/L) increased mRNA abundance of SLC38A2/SNAT2 (P ≤ 0.043) and SLC7A5/LAT1 (P ≤ 0.021) at 240 min and SLC36A1/PAT1 (P = 0.039) at 30 min. High rapamycin prevented an increase in SLC38A2/SNAT2 (P = 0.075) and SLC36A1/PAT1 (P ≥ 0.06) mRNA abundance whereas both rapamycin doses prevented an increase in SLC7A5/LAT1 (P ≥ 0.902) mRNA abundance. We conclude that a low insulin concentration increases SLC7A5/LAT1 mRNA abundance in an mTORC1-dependent manner in skeletal muscle cells.

    Original languageEnglish (US)
    Article numbere00238
    JournalPhysiological reports
    Volume2
    Issue number3
    DOIs
    StatePublished - 2014

    Keywords

    • C2C12 myotubes
    • PAT1
    • Rapamycin
    • SLC7A5
    • SNAT2

    ASJC Scopus subject areas

    • Physiology
    • Physiology (medical)

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  • Cite this

    Walker, D. K., Drummond, M. J., Dickinson, J., Borack, M. S., Jennings, K., Volpi, E., & Rasmussen, B. B. (2014). Insulin increases mRNA abundance of the amino acid transporter SLC7A5/LAT1 via an mTORC1-dependent mechanism in skeletal muscle cells. Physiological reports, 2(3), [e00238]. https://doi.org/10.1002/phy2.238