Genetic disruption of AMPK signaling abolishes both contraction- and insulin-stimulated TBC1D1 phosphorylation and 14-3-3 binding in mouse skeletal muscle

Christian Pehmøller, Jonas Thue Treebak, Jesper Bratz Birk, Shuai Chen, Carol Mackintosh, D. Grahame Hardie, Erik A. Richter, Jørgen Wojtaszewski

    Research output: Contribution to journalJournal articleResearchpeer-review

    140 Citations (Scopus)

    Abstract

    TBC1D1 is a Rab-GTPase-activating protein (GAP) known to be phosphorylated in response to insulin, growth factors, pharmacological agonists that activate 5'-AMP-activated protein kinase (AMPK), and muscle contraction. Silencing TBC1D1 in L6 muscle cells by siRNA increases insulin-stimulated GLUT4 translocation, and overexpression of TBC1D1 in 3T3-L1 adipocytes with low endogenous TBC1D1 expression inhibits insulin-stimulated GLUT4 translocation, suggesting a role of TBC1D1 in regulating GLUT4 translocation. Aiming to unravel the regulation of TBC1D1 during contraction and the potential role of AMPK in intact skeletal muscle, we used EDL muscles from wild-type (WT) and AMPK kinase dead (KD) mice. We explored the site-specific phosphorylation of TBC1D1 Ser(237) and Thr(596) and their relation to 14-3-3 binding, a proposed mechanism for regulation of GAP function of TBC1D1. We show that muscle contraction increases 14-3-3 binding to TBC1D1 as well as phosphorylation of Ser(237) and Thr(596) in an AMPK-dependent manner. AMPK activation by AICAR induced similar Ser(237) and Thr(596) phosphorylation of, and 14-3-3 binding to, TBC1D1 as muscle contraction. Insulin did not increase Ser(237) phosphorylation or 14-3-3 binding to TBC1D1. However, insulin increased Thr(596) phosphorylation, and intriguingly this response was fully abolished in the AMPK KD mice. Thus, TBC1D1 is differentially regulated in response to insulin and contraction. This study provides genetic evidence to support an important role for AMPK in regulating TBC1D1 in response to both of these physiological stimuli.
    Original languageEnglish
    JournalAmerican Journal of Physiology: Endocrinology and Metabolism
    Volume297
    Issue number3
    Pages (from-to)E665-E675
    Number of pages11
    ISSN0193-1849
    DOIs
    Publication statusPublished - 2009

    Cite this