Our group previously demonstrated that an excess of nutrients, as observed in diabetes, provokes an increase in cardiac protein acetylation responsible for a reduced insulin-stimulated translocation of the glucose transporter GLUT4 to the plasma membrane. The acetylated proteins involved in this event have yet not been identified. α-Tubulin is a promising candidate as a major cytoskeleton component involved, among other things, in the translocation of GLUT4-containing vesicles from their intracellular pools toward the plasma membrane. Moreover, α-tubulin is known to be acetylated, Lys40 (K40) being its best characterized acetylated residue. The present work sought to evaluate the impact of α-tubulin K40 acetylation on cardiac glucose entry, with a particular interest in GLUT4 translocation. First, we observed that a mouse model of high-fat diet-induced obesity presented an increase in cardiac α-tubulin K40 acetylation level. We next showed that treatment of insulin-sensitive primary cultured adult rat cardiomyocytes with tubacin, a specific tubulin acetylation inducer, reduced insulin-stimulated glucose uptake and GLUT4 translocation. Conversely, decreasing α-tubulin K40 acetylation by expressing a nonacetylable dominant form of α-tubulin (mCherry α-tubulin K40A mutant) remarkably intensified insulin-induced glucose transport. Finally, mCherry α-tubulin K40A expression similarly improved glucose transport in insulin-resistant cardiomyocytes or after AMP-activated protein kinase activation. Taken together, our study demonstrates that modulation of α-tubulin K40 acetylation level affects glucose transport in cardiomyocytes, offering new putative therapeutic insights regarding modulation of glucose metabolism in insulin-resistant and diabetic hearts.NEW & NOTEWORTHY Acetylation level of α-tubulin on K40 is increased in the heart of a diet-induced mouse model of type 2 diabetes. Pharmacological stimulation of α-tubulin K40 acetylation lowers insulin-mediated GLUT4 vesicles translocation to the plasma membrane, reducing glucose transport. Expressing a nonacetylable dominant form of α-tubulin boosts glucose uptake in both insulin-sensitive and insulin-resistant cardiomyocytes.
Keywords: GLUT4; acetylation; cardiac metabolism; glucose uptake; tubulin.