Fig. 1: Decreased eIF2B activity induces s-ISR.
From: Plasticity of the mammalian integrated stress response
a, The prevailing view is that ISR induction downstream of the eIF2α kinases represents a linear response comprising increased eIF2α-p and subsequent decrease in eIF2B activity (c-ISR, orange). It is not clear whether decreased eIF2B activity without an increase in eIF2α-p such as in leukodystrophies (s-ISR, pink) induces comparable ISR to the eIF2α-p induction (orange). b,f, Western blot analysis of the denoted proteins, in MEFs treated with the indicated shRNAs for specified times or Tg (400 nM). In f, Tg (0 h) refers to control MEFs, not treated with control shRNAs. Representative images (n = 3 independent experiments) are shown. c,d, eIF2B GEF activity (c) and protein synthesis measured by [35S]methionine and cysteine incorporation (d) in MEFs expressing control shRNA or Eif2b5 shRNA, or treated with Tg (400 nM, 1 h), as indicated. Statistical significance was determined by two-tailed Student’s t-test. Data are presented as mean ± s.e.m. (n = 3 independent experiments). e, Fluorescence micrographs of MEFs treated with a vehicle (control), sodium arsenite (1 mM, 1 h) or Tg (400 nM, 1 h) or expressing control or Eif2b5 shRNAs (day 4), and stained with the indicated antibodies. Scale bar, 20 μm for all images. Representative images are shown (n = 3 independent experiments). g, Left, polysome profile tracings obtained by monitoring absorbance (254 nm) across 10–50% sucrose gradients. Right, distribution of the indicated mRNAs on polysomes isolated from MEFs expressing control, Eif2b5 or Eif2b5 + Eif4e shRNAs, as indicated. Representative data (n = 3 independent experiments) are shown.
