Eukaryotic Initiation Factor 2 Phosphorylation and Translational Control in Metabolism

Regulation of mRNA translation is a rapid and effective means to couple changes in the cellular environment with global rates of protein synthesis. In response to stresses, such as nutrient deprivation and accumulation of misfolded proteins in the endoplasmic reticulum, phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (elF2 alpha similar to P) reduces general translation initiation while facilitating the preferential translation of select transcripts, such as that encoding activating transcription factor 4 (ATF4), a transcriptional activator of genes subject to the integrated stress response (ISR). In this review, we highlight the translational control processes regulated by nutritional stress, with an emphasis on the events triggered by elF2 alpha similar to P, and describe the family of eukaryotic initiation factor 2 kinases and the mechanisms by which each sense different stresses. We then address 3 questions. First, what are the mechanisms by which elF2 alpha similar to P confers preferential translation on select mRNA and what are the consequences of the gene expression induced by the ISR? Second, what are the molecular processes by which certain stresses can differentially activate elF2 alpha similar to P and ATF4 expression? The third question we address is what are the modes of cross-regulation between the ISR and other stress response pathways, such as the unfolded protein response and mammalian target of rapamycin, and how do these regulatory schemes provide for gene expression programs that are tailored for specific stresses? This review highlights recent advances in each of these areas of research, emphasizing how elF2 alpha similar to P and the ISR can affect metabolic health and disease. Adv. Nutr. 3:307-321, 2012.