Overexpression of 14-3-3ζ Increases Brain Levels of C/EBP Homologous Protein CHOP

Allosteric regulation of protein 14-3-3ζ scaffold by small-molecule editing modulates histone H3 post-translational modifications

Background: Histone post-translational modifications (PTMs) are involved in various biological processes such as transcriptional activation, chromosome packaging, and DNA repair. Previous studies mainly focused on PTMs by directly targeting histone-modifying enzymes such as HDACs and HATs.

Methods and Results: In this study, we discovered a previously unexplored regulation mechanism for histone PTMs by targeting transcription regulation factor 14-3-3ζ. Mechanistic studies revealed 14-3-3ζ dimerization as a key prerequisite, which could be dynamically induced via an allosteric effect. The selective inhibition of 14-3-3ζ dimer interaction with histone H3 modulated histone H3 PTMs by exposing specific modification sites including acetylation, trimethylation, and phosphorylation, and reprogrammed gene transcription profiles for autophagy-lysosome function and endoplasmic reticulum stress.

Conclusion: Our findings demonstrate the feasibility of editing histone PTM patterns by targeting transcription regulation factor 14-3-3ζ, and provide a distinctive PTM editing strategy which differs from current histone modification approaches.

14-3-3ζ protein protects against brain ischemia/reperfusion injury and induces BDNF transcription after MCAO in rat

Brain ischemia is a leading cause of death and disability worldwide that occurs when blood supply of the brain is disrupted. Brain-derived neurotrophic factor (BDNF) is a protective factor in neurodegenerative conditions. Nevertheless, there are some problems when exogenous BDNF is to be used in the clinic. 14-3-3ζ is a pro-survival highly-expressed protein in the brain that protects neurons against death. This study evaluates 14-3-3ζ effects on BDNF transcription at early time point after ischemia and its possible protective effects against ischemia damage. Human 14-3-3ζ protein was purified after expression. Rats were assigned into four groups, including sham, ischemia, and two treatment groups. Stereotaxic cannula implantation was carried out in the right cerebral ventricle. After one week, rats underwent middle cerebral artery occlusion (MCAO) surgery and received 14-3-3ζ (produced in our laboratory or standard form as control) in the middle of ischemia time. At 6 h of reperfusion after ischemia, brain parts containing the hippocampus, the cortex, the piriform cortex-amygdala and the striatum were collected for real time PCR analysis. At 24 h of reperfusion after ischemia, neurological function evaluation and infarction volume measurement were performed. The present study showed that 14-3-3ζ could up-regulate BDNF mRNA at early time point after ischemia in the hippocampus, in the cortex and in the piriform cortex-amygdala and could also improve neurological outcome and reduce infarct volume. It seems that 14-3-3ζ could be a candidate factor for increasing endogenous BDNF in the brain and a potential therapeutic factor against brain ischemia.

RNA sequencing of synaptic and cytoplasmic Upf1-bound transcripts supports contribution of nonsense-mediated decay to epileptogenesis

The nonsense mediated decay (NMD) pathway is a critical surveillance mechanism for identifying aberrant mRNA transcripts. It is unknown, however, whether the NMD system is affected by seizures in vivo and whether changes confer beneficial or maladaptive responses that influence long-term outcomes such the network alterations that produce spontaneous recurrent seizures. Here we explored the responses of the NMD pathway to prolonged seizures (status epilepticus) and investigated the effects of NMD inhibition on epilepsy in mice. Status epilepticus led to increased protein levels of Up-frameshift suppressor 1 homolog (Upf1) within the mouse hippocampus. Upf1 protein levels were also higher in resected hippocampus from patients with intractable temporal lobe epilepsy. Immunoprecipitation of Upf1-bound RNA from the cytoplasmic and synaptosomal compartments followed by RNA sequencing identified unique populations of NMD-associated transcripts and altered levels after status epilepticus, including known substrates such as Arc as well as novel targets including Inhba and Npas4. Finally, long-term video-EEG recordings determined that pharmacologic interference in the NMD pathway after status epilepticus reduced the later occurrence of spontaneous seizures in mice. These findings suggest compartment-specific recruitment and differential loading of transcripts by NMD pathway components may contribute to the process of epileptogenesis.

Dual and Opposing Roles of MicroRNA-124 in Epilepsy Are Mediated through Inflammatory and NRSF-Dependent Gene Networks

Insult-provoked transformation of neuronal networks into epileptic ones involves multiple mechanisms. Intervention studies have identified both dysregulated inflammatory pathways and NRSF-mediated repression of crucial neuronal genes as contributors to epileptogenesis. However, it remains unclear how epilepsy-provoking insults (e.g., prolonged seizures) induce both inflammation and NRSF and whether common mechanisms exist. We examined miR-124 as a candidate dual regulator of NRSF and inflammatory pathways. Status epilepticus (SE) led to reduced miR-124 expression via SIRT1--and, in turn, miR-124 repression--via C/EBPα upregulated NRSF. We tested whether augmenting miR-124 after SE would abort epileptogenesis by preventing inflammation and NRSF upregulation. SE-sustaining animals developed epilepsy, but supplementing miR-124 did not modify epileptogenesis. Examining this result further, we found that synthetic miR-124 not only effectively blocked NRSF upregulation and rescued NRSF target genes, but also augmented microglia activation and inflammatory cytokines. Thus, miR-124 attenuates epileptogenesis via NRSF while promoting epilepsy via inflammation.