Cystatin C, a cysteine protease inhibitor was chosen as a model protein, since its secretion ensures a relative short intracellular residency time so that its intracellular levels directly reflect its synthesis rate [55] . This is confirmed by the N-glycosylated-and total Cystatin C accumulation in cells treated with brefeldin A (Fig. 4A , left panel). Cystatin C levels were found to follow a similar trend to that observed with total translation, being strongly reduced upon poly I:C exposure and not profoundly influenced by GADD34 inactivation (Fig. 4A, right panel) . Thapsigargin treatment induced a brief drop in cystatin C levels, prior to some levels of GADD34-dependent recovery. 6 hours of tunicamycin treatment affected more cystatin C accumulation than anticipated Figure 3 . GADD34 mediates eIF2a dephosphorylation but not global translation recovery in response to poly I:C. A) After treatment with poly I:C, protein extracts of WT and GADD34 DC/DC MEFs were immunobloted for GADD34 and P-eIF2a. B) Protein synthesis was analyzed in WT cells treated for 1 to 6 hours with poly I:C (pI:C) alone or together with thapsigargin (th). Controls are cells not treated with puromycin (co) and cells treated with cycloheximide (chx) 5 min before puromycin incorporation. C) Protein synthesis was analyzed in GADD34 DC/DC cells treated for 1 to 6 hours with poly I:C (pI:C) alone or together with thapsigargin (th). Tubulin or b-actin immunoblot are shown for equal loading control. In GADD34 DC/DC cells translation is strongly impacted by thapsigargin, but not poly I:C. doi:10.1371/journal.ppat.1002708.g003 Fig. 4A, right panel) , probably due to interference with the Nglycosylation and associated folding of this di-sulfide bridge containing protein [55] , thereby promoting its degradation by endoplasmic reticulum-associated protein degradation (ERAD) [56] .