Grant: Discovery Grants Program - Individual

This program will discover and define eukaryotic protein elongation factor 1A1 (EEF1A1)-dependent links between regulation of the actin cytoskeleton and cell metabolism. Characterizing a previously unknown role for EEF1A1 in orchestrating cell metabolism could change the way we view the regulation and plasticity of metabolism in tissues with high energy requirements, such as those of the heart. EEF1A1 is robustly expressed in most adult tissues, except heart and skeletal muscle. It promotes aa-tRNA-ribosome binding, but also controls actin cytoskeleton remodelling and in responses to cell stress, including exposure to high fatty acids. We previously discovered that chemical inhibition or genetic ablation of EEF1A1 imparts a preference for fatty acid utilization. Inhibition of EEF1A1 decreased liver lipids in mice fed high fat diet, in association with gene changes consistent with increased fatty acid oxidation. RNA-Seq analyses of EEF1A1-deficient CHO-K1 cells revealed significant downregulation of glycolytic enzymes. Functional assays confirmed that these cells preferentially rely on oxidative metabolism. EEF1A1-deficient CHO-K1 cells do not exhibit impaired total protein synthesis, because the closely related EEF1A2 isoform compensates for this function. But these cells do exhibit markedly altered actin cytoskeleton, with a 40% increase in polymerized actin. Since the actin cytoskeleton can regulate glycolytic enzyme activity, EEF1A1 may affect cellular metabolism through its actin cytoskeleton-regulating function. Short-Term Objectives: 1. Determine the mechanism whereby EEF1A1 controls cellular metabolism. Binding of glycolytic enzymes to polymerized actin negatively regulates their activity. We will determine whether EEF1A1 controls cellular metabolism by regulating the retention of glycolytic enzymes at the actin cytoskeleton. 2. Investigate the EEF1A1-dependence of metabolic substrate preference in myocardium during development. Developing myocardium expresses EEF1A1 and 2 and is highly glycolytic, but mature myocardium expresses mainly EEF1A2 and relies on oxidative metabolism. We will determine whether this metabolic switch depends on the developmental decline in EEF1A1 expression. Long-Term Goal: Further to these short-term objectives, we will explore whether an EEF1A1-actin cytoskeleton axis underlies global tissue metabolic plasticity. We will obtain transgenic Eef1a1-EGFP mice (MMRRC, NIH) which express EGFP in all cells where the Eef1a1 promoter is activated. Time-course analyses of EGFP expression during development of heart, skeletal muscle, and brain will guide corresponding evaluations of metabolic substrate preferences and actin cytoskeleton dynamics. These studies will inform cell-specific and inducible expression strategies to determine the EEF1A1-dependency of metabolic plasticity during development.