Nck-1 Antagonizes the Endoplasmic Reticulum Stress-induced Inhibition of Translation

Abstract

Eukaryotic cells have developed specific mechanisms to overcome environmental stress. Here we show that the Src homology 2/3 (SH2/SH3) domain-containing protein Nck-1 prevents the unfolded protein response normally induced by pharmacological endoplasmic reticulum (ER) stress agents. Overexpression of Nck-1 enhances protein translation, whereas it abrogates eukaryotic initiation factor 2␣ (eIF2␣) phosphorylation and inhibition of translation in response to tunicamycin or thapsigargin treatment. Nck-1 overexpression also attenuates induction of the ER chaperone, the immunoglobulin heavy chain-binding protein (BiP), and impairs cell survival in response to thapsigargin. We provided evidence that in these conditions, the effects of Nck on the unfolded protein response (UPR) involve its second SH3 domain and a calyculin A-sensitive phosphatase activity. In addition, we demonstrated that protein translation is reduced in mouse embryonic fibroblasts lacking both Nck isoforms and is enhanced in similar cells expressing high levels of Nck-1. In these various mouse embryonic fibroblasts, we also provided evidence that Nck modulates the activation of the ER resident eIF2␣ kinase PERK and consequently the phosphorylation of eIF2␣ on Ser-51 in response to stress. Our study establishes that Nck is required for optimal protein translation and demonstrates that, in addition to its adaptor function in mediating signaling from the plasma membrane, Nck also mediates signaling from the ER membrane compartment.

Tyrosine phosphorylation acts as a molecular switch to full-scale activation of the eIF2α RNA-dependent protein kinase

“…Another possibility is that tyrosine phosphorylation is needed for the signaling properties of PKR through interactions with Src homology 2-containing proteins that could serve as substrates of the kinase. Consistent with this notion, it is of interest that the Src homology 2 containing protein Nck-1 controls mRNA translation through its functional and physical interactions with eIF2 (19,20).…”

Src homology domain 2 adaptors affect adherence of Salmonella enterica serovar Typhimurium to non-phagocytic cells

“…One way Nck and ShcA could affect the host cell surface is through modulating protein expression. Nck1 has been shown to enhance protein translation through its interaction with eukaryotic initiation factor 2 (eIF2) (Kebache et al, 2002(Kebache et al, , 2004Latreille & Larose, 2006). Accordingly, perhaps Nck is involved in the expression of the S. Typhimurium receptor.…”

Cellular response to endoplasmic reticulum stress: a matter of life or death

“…123 More recently, the SH2/SH3 domain-containing protein Nck-1 has been shown to antagonize PERK signaling in a phosphatasedependent manner, probably through the direct dephosphorylation of activated PERK itself. 124 Nck-1 activity also results in the dephosphorylation of eIF2a though whether it does so indirectly, by inactivating PERK, or directly, by mediating eIF2a dephosphorylation (or both), remains to be determined. 124 The bZIP transcription factor Nrf2 was recently identified as a second substrate of PERK.…”

“…124 Nck-1 activity also results in the dephosphorylation of eIF2a though whether it does so indirectly, by inactivating PERK, or directly, by mediating eIF2a dephosphorylation (or both), remains to be determined. 124 The bZIP transcription factor Nrf2 was recently identified as a second substrate of PERK. 125 Upon ESR induction, PERK phosphorylation causes Nrf2 to relocalize from the cytoplasm to the nucleus, where it upregulates a range of antioxidant response genes.…”