Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2018-2019)

Translation of mRNAs under stress like DNA damage, oxidative stress, nutritional stress or endoplasmic reticulum (ER) stress determines cell fate through the induction of either cell cycle arrest or death. An important mechanism of translational regulation under stress involves the phosphorylation of the alpha (α) subunit of the translation initiation factor eIF2 at serine (S) 51 ( eIF2αP ). Increased eIF2αP is mediated by a family of four kinases, namely HRI, PKR, GCN2 and PERK, each of which responds to different forms of stress and constitute a biological process known as the integrated stress response ( ISR ). eIF2αP is a master regulator of stress through its ability to inhibit proliferation in order to allow cells repair the damage caused by stress and help them adapt to chronic stress. If, however, the damage is beyond repair, eIF2αP programs the elimination of cells by death. Mechanistically, increased eIF2αP leads to a general inhibition of mRNA translation but also facilitates the translation of select mRNAs encoding proteins that promote the survival and adaptation of cells to mild or chronic stress, or cause cell death under severe stress.

My lab has made important contributions to the field by discovering novel mechanisms utilized by eIF2α kinases to sense stress and induce eIF2αP leading to regulation of mRNA translation. For example, we demonstrated molecular modifications of eIF2α kinases (e.g. tyrosine phosphorylation) and functional interactions with pro-survival pathways (PI3K-AKT-mTOR, HIPPO) that determine their optimal activation and function in mRNA translation and cell fate. However, it remains unknown how a single phosphorylation of eIF2α can dictate such distinct biological outcomes (cell survival versus death). We hypothesize that the eIF2α kinases are capable of mediating the phosphorylation of different proteins in addition to eIF2α, which can dictate the life or death decisions of eIF2αP under stress .

We have engineered cells to express conditionally active chimeric forms of either PKR or PERK, which faithfully imitate their activation under stress. The cells will be employed for the identification of phosphoproteins in whole protein extracts as well as phosphoproteins bound to eIF2 in response to kinase activation by the implementation of stable isotope labeling by amino acids in cell culture (SILAC) and mass spectrometry (MS). We will also apply chemical biology approaches to modify PERK and PKR for the identification of novel substrates in vitro and cultured cells. Apart from addressing a fundamental question in signaling to and regulation of mRNA translation under various forms of environmental stress, our work will lead to excellent training of graduate students in a vibrant research environment that provides access to cutting edge technology and fosters education for the successful training and career development of the new generation of scientists.