Chronically stressed or stress-preconditioned neurons fail to maintain stress granule assembly

Abstract

Dysregulation of stress granules (SGs) and their resident proteins contributes to pathogenesis of a number of (neuro)degenerative diseases. Phosphorylation of eIF2α is an event integrating different types of cellular stress and it is required for SG assembly. Phosphorylated eIF2α (p-eIF2α) is upregulated in the nervous system in some neurodegenerative conditions. We found that increasing p-eIF2α level by proteasomal inhibition in cultured cells, including mouse and human neurons, before a SG-inducing stress (‘stress preconditioning’), limits their ability to maintain SG assembly. This is due to upregulation of PP1 phosphatase regulatory subunits GADD34 and/or CReP in preconditioned cells and early decline of p-eIF2α levels during subsequent acute stress. In two model systems with constitutively upregulated p-eIF2α, mouse embryonic fibroblasts lacking CReP and brain neurons of tau transgenic mice, SG formation was also impaired. Thus, neurons enduring chronic stress or primed by a transient mild stress fail to maintain p-eIF2α levels following subsequent acute stress, which would compromise protective function of SGs. Our findings provide experimental evidence on possible loss of function for SGs in certain neurodegenerative diseases.

Stress granules regulate stress-induced paraspeckle assembly

“…This indicates that SG-mediated signaling, rather than cellular stress signaling per se, regulates PS assembly. In support of this, a short, 10-min NaAsO 2 exposure, which is sufficient to trigger stress signaling and increase p-eIF2α levels (Shelkovnikova et al, 2017) but does not induce SGs, failed to increase PS numbers ( Fig. S2 E).…”

Antiviral Immune Response as a Trigger of FUS Proteinopathy in Amyotrophic Lateral Sclerosis

“…Moreover, all of these stressors cause an acute response that, if not resolved after a short period (usually up to several hours), kills the cell. In most instances, SGs eventually disassemble to allow restoration of translation, even if the stress persists (Shelkovnikova et al, 2017). SG-inducing viral infections are principally different in this regard, because they result in prolonged and, in some cases, oscillating SG response, which allows phases of active and stalled translation and FUS fragment but increased intensity of the smear corresponding to the longer PA tails; the intensity profile of the PA tail lanes is also shown.…”

“…Western blots were re-probed for b-actin as a control for equal loading. Protein labeling with puromycin was performed as described earlier (Shelkovnikova et al, 2017).…”

“…SH-SY5Y cells and human fibroblasts were grown in high-glucose 1:1 mixture of DMEM/F12 supplemented with 10% fetal bovine serum (FBS), 1% penicillin-streptomycin and 2 mM L-glutamine (all Invitrogen). Human motor neuron differentiation from ES cells (H9 line, female) is described in a previous study (Shelkovnikova et al, 2017).…”

Chronic starvation induces non-canonical pro-death stress granules

“…To model chronic stress, we employed an existing definition of this state within the literature as stress typically lasting a duration of greater than 4 h (Guan et al, 2017;Shelkovnikova et al, 2017). We utilized a chronic nutrient starvation stress, in which cells were starved of glucose, serum, glutamine and pyruvate.…”