Abstract 13103: A Novel Anchor Protein TUG Mediates GLUT4 Translocation by AMP-activated Protein Kinase in the Ischemic Heart
Introduction: Ischemic heart disease is a leading cause of death, and it is caused by reduced blood flow to the ischemic area. Thus, an increasing nutrient uptake is a key approach to increase cardiomyocyte survival rate during the ischemia and reperfusion (I/R) period. TUG (tether containing a UBX domain, for GLUT4, 60 KDa) is a regulator of GLUT4 trafficking, it can be cleaved to mobilize GLUT4 from intracellular membranes to the cell surface after insulin stimulation in skeletal muscle. The energy sensor AMP-activated protein kinase (AMPK) is known to play an important cardioprotective role during myocardial I/R by regulating GLUT4 translocation and glucose uptake.
Hypothesis: TUG is one of the downstream targets of AMPK, which can be phosphorylated by hypoxia/ischemia induced AMPK activation. Phosphorylation of TUG accelerates its cleavage and increases GLUT4 translocation during ischemia/reperfusion in the heart.
Methods: In vitro hypoxia chamber and ex vivo isolated mouse heart perfusion Langendorff system were used to test the hypothesis. Antithrombin (AT) is an endogenous AMPK agonist in the heart, which was used to define the role of TUG in regulating GLUT4 trafficking during ischemia and reperfusion in the heart.
Results: The ex vivo heart perfusion data demonstrated that AT triggered AMPK activation and significantly increase glucose uptake and GLUT4 translocation during ischemia and reperfusion (p<0.05 vs. vehicle). Intriguingly, GLUT4 immunoprecipitation data showed that AT treatment caused a dissociation of TUG from GLUT4. Moreover, AT treatment increased abundance of a TUG cleavage product (42 KDa) in response to I/R. All of these glucose transporter trafficking events are blunted in the AMPK kinase dead (KD) transgenic hearts. In HL-1 cardiomyocytes, TUG proteins were phosphorylated by activated AMPK during hypoxia. Moreover, TUG siRNA knockdown the TUG of HL-1 cells caused significantly increased cell surface GLUT4 and glucose uptake.
Conclusions: Cardiac AMPK activation stimulates TUG cleavage and causes the dissociation between TUG and GLUT4 in the intracellular vesicles. TUG is a critical mediator that modulates cardiac GLUT4 translocation to cell surface and enhances glucose uptake by AMPK signaling pathway.
Author Disclosures: Y. Ma: None. W. Sun: None. N. Quan: None. L. Wang: None. X. Chen: None. J. Bogan: None. J. Li: None.
- © 2015 by American Heart Association, Inc.