Ectopic expression of eukaryotic initiation factor 2B epsilon (eIF2Bε) in rat skeletal muscle rescues the sepsis‐induced reduction in guanine nucleotide exchange activity and protein synthesis

Abstract

eIF2B is a guanine nucleotide exchange factor (GEF) whose activity is both tightly regulated and rate controlling with regard to global protein synthesis rates. Skeletal muscle eIF2B activity and catalytic epsilon subunit (eIF2Bε) expression have been implicated as potential contributors to the altered rates of protein synthesis in a number of physiological and experimental models. The objective of the current study was to directly examine the effects of exogenously expressed eIF2Bε in vivo on GEF activity and protein synthetic rates in rat skeletal muscle. A plasmid encoding FLAG‐eIF2Bε was transfected into the tibialis anterior (TA) of one leg while the contralateral TA received a control plasmid. Ectopic expression of eIF2Bε resulted in increased GEF activity in TA homogenates of healthy rats demonstrating that the expressed protein was catalytically active. In an effort to restore a deficit in eIF2B activity, we utilized an established model of chronic sepsis in which skeletal muscle eIF2B activity is known to be impaired. Ectopic expression of eIF2Bε in the TA of septic rats rescued the deficit in GEF activity and muscle protein synthesis caused by sepsis. The results demonstrate that ectopic expression of eIF2Bε may be sufficient to rescue the sepsis‐induced reduction in skeletal muscle protein synthesis. (Supported by grants DK15658, GM 39277 and the PA Department of Health).