RESUMEN

Eukaryotic initiation factor 2B (eIF2B) controls translation initiation by recycling inactive eIF2-GDP to active eIF2-GTP. Under cellular stress, the integrated stress response (ISR) is activated inhibiting eIF2B activity resulting in the translation attenuation and reprogramming of gene expression to overcome the stress. The ISR can dictate cell fate wherein chronic activation has pathological outcomes. Vanishing white matter disease (VWMD) is a chronic ISR-related disorder with mutations in eIF2B targeting astrocyte and oligodendrocyte cells. Regulation of eIF2B localization (eIF2B bodies) has been implicated in the ISR. We present evidence that neuronal and glial cell types possess distinct patterns of eIF2B bodies which change in a manner correlating to acute and chronic ISR activation. We also demonstrate that while neural and glial cell types respond similarly to the acute induction of the ISR a chronic ISR exerts cell-type specific differences. These findings provide key insights into neural cell responses and adaptation to cellular stress.

RESUMEN

Eukaryotic initiation factor 2B, eIF2B is a guanine nucleotide exchange, factor with a central role in coordinating the initiation of translation. During stress and disease, the activity of eIF2B is inhibited via the phosphorylation of its substrate eIF2 (p-eIF2α). A number of different kinases respond to various stresses leading to the phosphorylation of the alpha subunit of eIF2, and collectively this regulation is known as the integrated stress response, ISR. This targeting of eIF2B allows the cell to regulate protein synthesis and reprogramme gene expression to restore homeostasis. Advances within structural biology have furthered our understanding of how eIF2B interacts with eIF2 in both the productive GEF active form and the non-productive eIF2α phosphorylated form. Here, current knowledge of the role of eIF2B in the ISR is discussed within the context of normal and disease states focusing particularly on diseases such as vanishing white matter disease (VWMD) and permanent neonatal diabetes mellitus (PNDM), which are directly linked to mutations in eIF2B. The role of eIF2B in synaptic plasticity and memory formation is also discussed. In addition, the cellular localisation of eIF2B is reviewed and considered along with the role of additional in vivo eIF2B binding factors and protein modifications that may play a role in modulating eIF2B activity during health and disease.

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This study uses integrated art and science events to explore a blended approach in improving public understanding of current scientific topics and widening participation within the local community. The events were a Halloween-inspired microbiology-themed series of interactive exhibitions hosted within a national museum as part of an existing series of adult education evenings. A representative sample of 102 mixed methods exit questionnaires, based on determining (i) audience diversity and (ii) understanding of scientific topics, were analysed by qualitative and quantitative approaches, and a post-attendance focus group was carried out to determine longer term impact of the event. Participants were grouped as 'Science', 'Arts', 'Both' or 'Neither', according to their past experience and engagement. These events welcomed more participants from the Arts and Neither subsections hence engaging a group of people who would not usually visit science public engagement events or comparative events hosted in traditional academic settings, highlighting the importance of venue choice in reaching new audiences and widening participation. An increase in perceived understanding of science was observed by all groups of participants with reported enjoyment focused around the science talks, presentations and blended art-science activities. A putative impact in science capital is observed with participants reporting an increased likelihood of attending science events in the future. Furthermore, increased discussion and awareness of science in society is evidenced by participants. Blended art and microbiology exhibitions enhance the accessibly of science public engagement events and is likely to increase science capital; the impact of this on cognitive polyphasia is also discussed.

RESUMEN

Eukaryotic initiation factor 2B (eIF2B) serves as a vital control point within protein synthesis and regulates translation initiation in response to cellular stress. Mutations within eIF2B result in the fatal disease, leukoencephalopathy with vanishing white matter (VWM). Previous biochemical studies on VWM mutations have illustrated that changes in the activity of eIF2B poorly correlate with disease severity. This suggests that there may be additional characteristics of eIF2B contributing to VWM pathogenesis. Here, we investigated whether the localization of eIF2B to eIF2B bodies was integral for function and whether this localization could provide insight into the pathogenesis of VWM. We demonstrate that the regulatory subunit, eIF2Bα, is required for the assembly of eIF2B bodies in yeast and that loss of eIF2B bodies correlates with an inability of cells to regulate eIF2B activity. Mutational analysis of eIF2Bα showed that missense mutations that disrupt the regulation of eIF2B similarly disrupt the assembly of eIF2B bodies. In contrast, when eIF2Bα mutations that impact the catalytic activity of eIF2B were analyzed, eIF2B bodies were absent and instead eIF2B localized to small foci, termed microfoci. Fluorescence recovery after photobleaching analysis highlighted that within these microfoci, eIF2 shuttles more slowly indicating that formation of eIF2B bodies correlates with full eIF2B activity. When eIF2Bα VWM mutations were analyzed, a diverse impact on localization was observed, which did not seem to correlate with eIF2B activity. These findings provide key insights into how the eIF2B body assembles and suggest that the body is a fundamental part of the translational regulation via eIF2α phosphorylation.

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RESUMEN

Eukaryotic initiation factor 2 (eIF2) is a G protein critical for translation. It is tightly regulated in the integrated stress response (ISR) via phosphorylation of eIF2α and the subsequent control of eukaryotic initiation factor 2B (eIF2B), a multisubunit guanine nucleotide exchange factor. Through studying the localization of eIF2B subunits, we identified cytoplasmic eIF2B bodies in mammalian cells. We highlight a relationship between body size and the eIF2B subunits localizing to them; larger bodies contain all subunits and smaller bodies contain predominantly catalytic subunits. eIF2 localizes to eIF2B bodies and shuttles within these bodies in a manner that correlates with eIF2B activity. On stress, eIF2α-P localizes predominately to larger bodies and results in a decreased shuttling of eIF2. Interestingly, drugs that inhibit the ISR can rescue eIF2 shuttling in a manner correlating to levels of eIF2α-P. In contrast, smaller bodies show increased eIF2 shuttling in response to stress, which is accompanied by the localization of eIF2Bδ to these bodies, suggesting the formation of a novel trimeric complex of eIF2B. This response is mimicked by ISR-inhibiting drugs, providing insight into their potential mechanism of action. This study provides evidence that the composition and function of mammalian eIF2B bodies are regulated by the ISR and the drugs that control it.

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We report of a family who has three members affected by medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, one of whom sadly died in the neonatal period prior to diagnosis. Routine sequencing, available on a service basis in the UK, identified only a heterozygous mutation in ACADM gene (c.985A>G, p.Lys329Glu) in this family. Linkage analysis suggested a possible intragenic deletion which was confirmed by the use of array-based comparative genomic hybridization (aCGH). This second mutation was a large intragenic deletion encompassing at least exons 1-6 of the ACADM gene. Now that this deletion has been identified, several family members have come forward for carrier testing which was not possible previously. Larger deletions (20bp or more) have only previously been reported twice, but these may be a more frequent cause of MCAD deficiency than hitherto believed, due to fact that these are not anticipated and, therefore, the routine diagnostic techniques used will not identify them. This finding represents a useful learning point in the management of families with MCAD deficiency, and highlights that we should be routinely looking for larger deletions, when only one of the mutations can be identified on standard sequencing.