Nrg1β is involved in cardiac development and also maintains function of the adult heart. Studies in animal models showed that it improves cardiac performance under a range of pathological conditions, which led to its introduction in clinical trials to treat heart failure. Recent work also implicated Nrg1β in the regenerative potential of neonatal and adult hearts. The molecular mechanisms whereby Nrg1β acts in cardiac cells are still poorly understood. In the present study we analyzed the effects of Nrg1β on glucose uptake in neonatal rat ventricular myocytes and investigated if mTOR/Akt signaling pathways are implicated. We show that Nrg1β enhances glucose uptake in cardiomyocytes as efficiently as IGF-I and insulin. Nrg1β causes phosphorylation of ErbB2 and ErbB4 and rapidly induces the phosphorylation of FAK (Y861), Akt (T308 and S473) and its effector AS160 (T642). Knock-down of ErbB2 or ErbB4 reduces Akt phosphorylation and blocks the glucose uptake. The Akt inhibitor VIII and the PI3K inhibitors LY294002 and Byl-719 abolish Nrg1β-induced phosphorylation and glucose uptake. Finally, specific mTORC2 inactivation after knockdown of rictor blocks the Nrg1β-induced increases in Akt-pS473, but does not modify AS160-pT642 and the glucose uptake responses to Nrg1β. In conclusion, we demonstrated that Nrg1β enhances glucose uptake in cardiomyocytes via ErbB2/ErbB4 heterodimers, PI3Kα and Akt. Furthermore, while Nrg1β activates mTORC2, the resulting Akt-S473 phosphorylation is not essential for glucose uptake induction. These new insights into pathways whereby Nrg1β regulates glucose uptake in cardiomyocytes may contribute to the understanding of its regenerative capacity and protective function in heart failure.
- heart failure
- tyrosine kinase
- Copyright © 2016, American Journal of Physiology - Endocrinology and Metabolism