Phosphorylation at tyrosine 262 promotes GADD34 protein turnover.

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In mammalian cells, metabolic and environmental stress increases the phosphorylation of the eukaryotic translational initiation factor, eIF2α, and attenuates global protein synthesis. Subsequent transcriptional activation of GADD34 assembles an eIF2α phosphatase that feeds back to restore mRNA translation. Active proteasomal degradation of GADD34 protein then reestablishes the sensitivity of cells to subsequent bouts of stress. Mass spectrometry established GADD34 phosphorylation on multiple serines, threonines, and tyrosines. Phosphorylation at tyrosine 262 enhanced the rate of the GADD34 protein turnover. Substrate-trapping studies identified TC-PTP (PTPN2) as a potential GADD34 phosphatase, recognizing phosphotyrosine 262. Reduced GADD34 protein levels in TC-PTP-null MEFs following ER stress emphasized the importance of TC-PTP in determining the cellular levels of GADD34 protein. The susceptibility of TC-PTP-null MEFs to ER stress-induced apoptosis was significantly ameliorated by ectopic expression of GADD34. The data suggested that GADD34 phosphorylation on tyrosine 262 modulates endoplasmic reticulum stress signaling and cell fate.





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Zhou, Wei, Krishna Jeyaraman, Permeen Yusoff and Shirish Shenolikar (2013). Phosphorylation at tyrosine 262 promotes GADD34 protein turnover. The Journal of biological chemistry, 288(46). pp. 33146–33155. 10.1074/jbc.m113.504407 Retrieved from

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Shirish Shenolikar

Professor Emeritus of Psychiatry and Behavioral Sciences

Protein phosphorylation controls a wide range of physiological processes in mammalian tissues. Phosphorylation state of cellular proteins is controlled by the opposing actions of protein kinases and phosphatases that are regulated by hormones, neurotransmitters, growth factors and other environmental cues. Our research attempts to understand the communication between protein kinases and phosphatases that dictates cellular protein phosphorylation and the cell's response to hormones. Over the last decade, our work has provided critical information about the role of protein phosphatase-1 (PP1) in controlling synaptic function, cell stress, gene expression and growth. We have generated a large repertoire of reagents to decipher PP1's role in signaling pathways in mammalian cells and tissues. Emerging evidence suggests that in many cells, PP1 activity is fine tuned by the protein, inhibitor-1 (I-1). A major focus of our research is to elucidate the role of I-1 in kinase-phosphatase cross-talk and impact of the altered I-1 gene expression seen in several human diseases. Our studies showed that recognition of cellular substrates by PP1 is also directed by its association with a variety of targeting subunits that are themselves also subject to physiological control. Thus, the overall focus of our research is to define the physiological mechanisms that regulate PP1 functions relevant to human health and disease.

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