The GCN2-ATF4 Signaling Pathway Induces 4E-BP to Bias Translation and Boost Antimicrobial Peptide Synthesis in Response to Bacterial Infection

DNA methylation of transposons pattern aging differences across a diverse cohort of dogs from the Dog Aging Project

Within a species, larger individuals often have shorter lives and higher rates of age-related disease. Despite this well-known link, we still know little about underlying age-related epigenetic differences, which could help us better understand inter-individual variation in aging and the etiology, onset, and progression of age-associated disease. Dogs exhibit this negative correlation between size, health, and longevity and thus represent an excellent system in which to test the underlying mechanisms. Here, we quantified genome-wide DNA methylation in a cohort of 864 dogs in the Dog Aging Project. Age strongly patterned the dog epigenome, with the majority (66% of age-associated loci) of regions associating age-related loss of methylation. These age effects were non-randomly distributed in the genome and differed depending on genomic context. We found the LINE1 (long interspersed elements) class of TEs (transposable elements) were the most frequently hypomethylated with age (FDR < 0.05, 40% of all LINE1 regions). This LINE1 pattern differed in magnitude across breeds of different sizes- the largest dogs lost 0.26% more LINE1 methylation per year than the smallest dogs. This suggests that epigenetic regulation of TEs, particularly LINE1s, may contribute to accelerated age and disease phenotypes within a species. Since our study focused on the methylome of immune cells, we looked at LINE1 methylation changes in golden retrievers, a breed highly susceptible to hematopoietic cancers, and found they have accelerated age-related LINE1 hypomethylation compared to other breeds. We also found many of the LINE1s hypomethylated with age are located on the X chromosome and are, when considering X chromosome inactivation, counter-intuitively more methylated in males. These results have revealed the demethylation of LINE1 transposons as a potential driver of intra-species, demographic-dependent aging variation.

Novel insights into the GCN2 pathway and its targeting. Therapeutic value in cancer and lessons from lung fibrosis development

Defining the mechanisms that allow cells to adapt to environmental stress is critical for understanding the progression of chronic diseases and identifying relevant drug targets. Among these, activation of the pathway controlled by the eIF2-alpha kinase GCN2 is critical for translational and metabolic reprogramming of the cell in response to various metabolic, proteotoxic, and ribosomal stressors. However, its role has frequently been investigated through the lens of a stress pathway signaling via the eIF2α-activating transcription factor 4 (ATF4) downstream axis, while recent advances in the field have revealed that the GCN2 pathway is more complex than previously thought. Indeed, this kinase can be activated through a variety of mechanisms, phosphorylate substrates other than eIF2α, and regulate cell proliferation in a steady state. This review presents recent findings regarding the fundamental mechanisms underlying GCN2 signaling and function, as well as the development of drugs that modulate its activity. Furthermore, by comparing the literature on GCN2's antagonistic roles in two challenging pathologies, cancer and pulmonary diseases, the benefits, and drawbacks of GCN2 targeting, particularly inhibition, are discussed.

High sugar diets can increase susceptibility to bacterial infection in Drosophila melanogaster

Overnutrition with dietary sugar can worsen infection outcomes in diverse organisms including insects and humans, through generally unknown mechanisms. In the present study, we show that adult Drosophila melanogaster fed high-sugar diets became more susceptible to infection by the Gram-negative bacteria Providencia rettgeri and Serratia marcescens. We found that P. rettgeri and S. marcescens proliferate more rapidly in D. melanogaster fed a high-sugar diet, resulting in increased probability of host death. D. melanogaster become hyperglycemic on the high-sugar diet, and we find evidence that the extra carbon availability may promote S. marcescens growth within the host. However, we found no evidence that increased carbon availability directly supports greater P. rettgeri growth. D. melanogaster on both diets fully induce transcription of antimicrobial peptide (AMP) genes in response to infection, but D. melanogaster provided with high-sugar diets show reduced production of AMP protein. Thus, overnutrition with dietary sugar may impair host immunity at the level of AMP translation. Our results demonstrate that dietary sugar can shape infection dynamics by impacting both host and pathogen, depending on the nutritional requirements of the pathogen and by altering the physiological capacity of the host to sustain an immune response.

Insulin receptor orchestrates kidney antibacterial defenses

Urinary tract infection (UTI) commonly afflicts people with diabetes. This augmented infection risk is partly due to deregulated insulin receptor (IR) signaling in the kidney collecting duct. The collecting duct is composed of intercalated cells (ICs) and principal cells (PCs). Evidence suggests that ICs contribute to UTI defenses. Here, we interrogate how IR deletion in ICs impacts antibacterial defenses against uropathogenic Escherichia coli. We also explore how IR deletion affects immune responses in neighboring PCs with intact IR expression. To accomplish this objective, we profile the transcriptomes of IC and PC populations enriched from kidneys of wild-type and IC-specific IR knock-out mice that have increased UTI susceptibility. Transcriptomic analysis demonstrates that IR deletion suppresses IC-integrated stress responses and innate immune defenses. To define how IR shapes these immune defenses, we employ murine and human kidney cultures. When challenged with bacteria, murine ICs and human kidney cells with deregulated IR signaling cannot engage central components of the integrated stress response-including activating transcriptional factor 4 (ATF4). Silencing ATF4 impairs NFkB activation and promotes infection. In turn, NFkB silencing augments infection and suppresses antimicrobial peptide expression. In diabetic mice and people with diabetes, collecting duct cells show reduced IR expression, impaired integrated stress response engagement, and compromised immunity. Collectively, these translational data illustrate how IR orchestrates collecting duct antibacterial responses and the communication between ICs and PCs.

The integrated stress response in metabolic adaptation

The integrated stress response (ISR) refers to signaling pathways initiated by stress-activated eIF2α kinases. Distinct eIF2α kinases respond to different stress signals, including amino acid deprivation and mitochondrial stress. Such stress-induced eIF2α phosphorylation attenuates general mRNA translation and, at the same time, stimulates the preferential translation of specific downstream factors to orchestrate an adaptive gene expression program. In recent years, there have been significant new advances in our understanding of ISR during metabolic stress adaptation. Here, I discuss those advances, reviewing among others the ISR activation mechanisms in response to amino acid deprivation and mitochondrial stress. In addition, I review how ISR regulates the amino acid metabolic pathways and how changes in the ISR impact the physiology and pathology of various disease models.

Interactions between innate immunity and insulin signaling affect resistance to infection in insects

An active immune response is energetically demanding and requires reallocation of nutrients to support resistance to and tolerance of infection. Insulin signaling is a critical global regulator of metabolism and whole-body homeostasis in response to nutrient availability and energetic needs, including those required for mobilization of energy in support of the immune system. In this review, we share findings that demonstrate interactions between innate immune activity and insulin signaling primarily in the insect model Drosophila melanogaster as well as other insects like Bombyx mori and Anopheles mosquitos. These studies indicate that insulin signaling and innate immune activation have reciprocal effects on each other, but that those effects vary depending on the type of pathogen, route of infection, and nutritional status of the host. Future research will be required to further understand the detailed mechanisms by which innate immunity and insulin signaling activity impact each other.

The Insulin Receptor and Insulin like Growth Factor Receptor 5' UTRs Support Translation Initiation Independently of EIF4G1

IRES mediated translation initiation requires a different repertoire of factors than canonical cap-dependent translation. Treatments that inhibit the canonical translation factor EIF4G1 have little or no effect on the ability of the Insr and Igf1r cellular IRESes to promote translation. Transcripts for two cellular receptors contain RNA elements that facilitate translation initiation without intact EIF4G1. Cellular IRES mechanisms may resemble viral type III IRESes allowing them to promote translate with a limited number of initiation factors allowing them to work under stress conditions when canonical translation is repressed.

Regulating metabolism to shape immune function: Lessons from Drosophila

Infection with pathogenic microbes is a severe threat that hosts manage by activating the innate immune response. In Drosophila melanogaster, the Toll and Imd signaling pathways are activated by pathogen-associated molecular patterns to initiate cellular and humoral immune processes that neutralize and kill invaders. The Toll and Imd signaling pathways operate in organs such as fat body and gut that control host nutrient metabolism, and infections or genetic activation of Toll and Imd signaling also induce wide-ranging changes in host lipid, carbohydrate and protein metabolism. Metabolic regulation by immune signaling can confer resistance to or tolerance of infection, but it can also lead to pathology and susceptibility to infection. These immunometabolic phenotypes are described in this review, as are changes in endocrine signaling and gene regulation that mediate survival during infection. Future work in the field is anticipated to determine key variables such as sex, dietary nutrients, life stage, and pathogen characteristics that modify immunometabolic phenotypes and, importantly, to uncover the mechanisms used by the immune system to regulate metabolism.

Multiple Roles of the Stress Sensor GCN2 in Immune Cells

The serine/threonine-protein kinase general control nonderepressible 2 (GCN2) is a well-known stress sensor that responds to amino acid starvation and other stresses, making it critical to the maintenance of cellular and organismal homeostasis. More than 20 years of research has revealed the molecular structure/complex, inducers/regulators, intracellular signaling pathways and bio-functions of GCN2 in various biological processes, across an organism's lifespan, and in many diseases. Accumulated studies have demonstrated that the GCN2 kinase is also closely involved in the immune system and in various immune-related diseases, such as GCN2 acts as an important regulatory molecule to control macrophage functional polarization and CD4⁺ T cell subset differentiation. Herein, we comprehensively summarize the biological functions of GCN2 and discuss its roles in the immune system, including innate and adaptive immune cells. We also discuss the antagonism of GCN2 and mTOR pathways in immune cells. A better understanding of GCN2's functions and signaling pathways in the immune system under physiological, stressful, and pathological situations will be beneficial to the development of potential therapies for many immune-relevant diseases.

Mitochondrial remodelling is essential for female germ cell differentiation and survival

Stem cells often possess immature mitochondria with few inner membrane invaginations, which increase as stem cells differentiate. Despite this being a conserved feature across many stem cell types in numerous organisms, how and why mitochondria undergo such remodelling during stem cell differentiation has remained unclear. Here, using Drosophila germline stem cells (GSCs), we show that Complex V drives mitochondrial remodelling during the early stages of GSC differentiation, prior to terminal differentiation. This endows germline mitochondria with the capacity to generate large amounts of ATP required for later egg growth and development. Interestingly, impairing mitochondrial remodelling prior to terminal differentiation results in endoplasmic reticulum (ER) lipid bilayer stress, Protein kinase R-like ER kinase (PERK)-mediated activation of the Integrated Stress Response (ISR) and germ cell death. Taken together, our data suggest that mitochondrial remodelling is an essential and tightly integrated aspect of stem cell differentiation. This work sheds light on the potential impact of mitochondrial dysfunction on stem and germ cell function, highlighting ER lipid bilayer stress as a potential major driver of phenotypes caused by mitochondrial dysfunction.

New Drosophila models to uncover the intrinsic and extrinsic factors that mediate the toxicity of the human prion protein

Misfolding of the prion protein (PrP) is responsible for devastating neurological disorders in humans and other mammals. An unresolved problem in the field is unraveling the mechanisms governing PrP conformational dynamics, misfolding, and the cellular mechanism leading to neurodegeneration. The variable susceptibility of mammals to prion diseases is a natural resource that can be exploited to understand the conformational dynamics of PrP. Here we present a new fly model expressing human PrP with new, robust phenotypes in brain neurons and the eye. By using comparable attP2 insertions, we demonstrated the heightened toxicity of human PrP compared to rodent PrP along with a specific interaction with the amyloid-β peptide. By using this new model, we started to uncover the intrinsic (sequence/structure) and extrinsic (interactions) factors regulating PrP toxicity. We described PERK (officially known as EIF2AK3 in humans) and activating transcription factor 4 (ATF4) as key in the cellular mechanism mediating the toxicity of human PrP and uncover a key new protective activity for 4E-BP (officially known as Thor in Drosophila and EIF4EBP2 in humans), an ATF4 transcriptional target. Lastly, mutations in human PrP (N159D, D167S, N174S) showed partial protective activity, revealing its high propensity to misfold into toxic conformations.

Drosophila Unfolded Protein Response (UPR) Assays In Vitro and In Vivo

Wildtype or mutant proteins expressed beyond the capacity of a cell's protein folding system could be detrimental to general cellular function and survival. In response to misfolded protein overload in the endoplasmic reticulum (ER), eukaryotic cells activate the Unfolded Protein Response (UPR) that helps cells restore protein homeostasis in the endoplasmic reticulum (ER). As part of the UPR, cells attenuate general mRNA translation and activate transcription factors that induce stress-responsive gene expression.UPR signaling draws research interest in part because conditions that cause chronic protein misfolding in the ER or those that impair UPR signaling underlie several diseases including neurodegeneration, diabetes, and cancers. Model organisms are frequently employed in the field as the UPR pathways are generally well-conserved throughout phyla. Here, we introduce experimental procedures to detect UPR in Drosophila melanogaster.

A Protein-trap allele reveals roles for Drosophila ATF4 in photoreceptor degeneration, oogenesis and wing development

Metazoans have evolved various quality control mechanisms to cope with cellular stress inflicted by external and physiological conditions. ATF4 is a major effector of the Integrated Stress Response (ISR), an evolutionarily conserved pathway that mediates adaptation to various cellular stressors. Loss of function of Drosophila ATF4, encoded by the gene cryptocephal (crc), results in lethality during pupal development. The roles of crc in Drosophila disease models and in adult tissue homeostasis thus remain poorly understood. Here, we report that a protein-trap MiMIC insertion in the crc locus generates a crc-GFP fusion protein that allows visualization of crc activity in vivo. This allele also acts as a hypomorphic mutant that uncovers previously unknown roles for crc. Specifically, the crc protein-trap line shows crc-GFP induction in a Drosophila model for Retinitis Pigmentosa (RP). This crc allele renders flies more vulnerable to amino acid deprivation and age-dependent retinal degeneration. These mutants also show defects in wing veins and oocyte maturation. Together, our data reveal previously unknown roles for crc in development, cellular homeostasis and photoreceptor survival.

Halofuginone triggers a transcriptional program centered on ribosome biogenesis and function in honey bees

We previously found that pharmacological inhibition of prolyl-tRNA synthetase by halofuginone has potent activity against Nosema ceranae, an important pathogen of honey bees. However, we also observed that prolyl-tRNA synthetase inhibition is toxic to bees, suggesting further work is necessary to make this a feasible therapeutic strategy. As expected, we found that pharmacological inhibition of prolyl-tRNA synthetase activity resulted in robust induction of select canonical ATF4 target genes in honey bees. However, our understanding of this and other cellular stress responses in general in honey bees is incomplete. Thus, we used RNAseq to identify novel changes in gene expression after halofuginone treatment and observed induction of genes involved in ribosome biogenesis, translation, tRNA synthesis, and ribosome-associated quality control (RQC). These results suggest that halofuginone, potentially acting through the Integrated Stress Response (ISR), promotes a transcriptional response to ribosome functional impairment in honey bees rather than the response designed to oppose amino acid limitation, which has been observed in other organisms after ISR induction. In support of this idea, we found that cycloheximide (CHX) administration also induced all tested target genes, indicating that this gene expression program could be induced by ribosome stalling in addition to tRNA synthetase inhibition. Only a subset of halofuginone-induced genes was upregulated by Unfolded Protein Response (UPR) induction, suggesting that mode of activation and cross-talk with other cellular signaling pathways significantly influence ISR function and cellular response to its activation. Future work will focus on understanding how the apparently divergent transcriptional output of the ISR in honey bees impacts the health and disease of this important pollinator species.

Impaired skeletal muscle hypertrophy signaling and amino acid deprivation response in Apoe knockout mice with an unhealthy lipoprotein distribution

This study explores if unhealthy lipoprotein distribution (LPD) impairs the anabolic and amino acid sensing responses to whey-protein feeding. Thus, if impairment of such anabolic response to protein consumption is seen by the LPD this may negatively affect the skeletal muscle mass. Muscle protein synthesis (MPS) was measured by puromycin labeling in Apolipoprotein E knockout (Apoe KO), characterized by an unhealthy LPD, and wild type mice post-absorptive at 10 and 20 weeks, and post-prandial after whey-protein feeding at 20 weeks. Hypertrophy signaling and amino acid sensing mechanisms were studied and gut microbiome diversity explored. Surprisingly, whey-protein feeding did not affect MPS. p-mTOR and p-4E-BP1 was increased 2 h after whey-protein feeding in both genotypes, but with general lower levels in Apoe KO compared to wild type. At 20 weeks of age, Apoe KO had a greater mRNA-expression for SNAT2, CD98, ATF4 and GCN2 compared to wild type. These responses were not associated with gut microbiota compositional differences. Regardless of LPD status, MPS was similar in Apoe KO and wild type. Surprisingly, whey-protein did not stimulate MPS. However, Apoe KO had lower levels of hypertrophy signaling, was amino acid deprived, and had impaired amino acid sensing mechanisms.

Dietary Adaptation of Microbiota in Drosophila Requires NF-κB-Dependent Control of the Translational Regulator 4E-BP

Dietary nutrients shape complex interactions between hosts and their commensal gut bacteria, further promoting flexibility in host-microbiota associations that can drive nutritional symbiosis. However, it remains less clear if diet-dependent host signaling mechanisms also influence these associations. Using Drosophila, we show here that nuclear factor κB (NF-κB)/Relish, an innate immune transcription factor emerging as a signaling node linking nutrient-immune-metabolic interactions, is vital to adapt gut microbiota species composition to host diet macronutrient composition. We find that Relish is required within midgut enterocytes to amplify host-Lactobacillus associations, an important bacterial mediator of nutritional symbiosis, and thus modulate microbiota composition in response to dietary adaptation. Relish limits diet-dependent transcriptional inducibility of the cap-dependent translation inhibitor 4E-BP/Thor to control microbiota composition. Furthermore, maintaining cap-dependent translation in response to dietary adaptation is critical to amplify host-Lactobacillus associations. These results highlight that NF-κB-dependent host signaling mechanisms, in coordination with host translation control, shape diet-microbiota interactions.

Reovirus and the Host Integrated Stress Response: On the Frontlines of the Battle to Survive

Cells are continually exposed to stressful events, which are overcome by the activation of a number of genetic pathways. The integrated stress response (ISR) is a large component of the overall cellular response to stress, which ultimately functions through the phosphorylation of the alpha subunit of eukaryotic initiation factor-2 (eIF2α) to inhibit the energy-taxing process of translation. This response is instrumental in the inhibition of viral infection and contributes to evolution in viruses. Mammalian orthoreovirus (MRV), an oncolytic virus that has shown promise in over 30 phase I–III clinical trials, has been shown to induce multiple arms within the ISR pathway, but it successfully evades, modulates, or subverts each cellular attempt to inhibit viral translation. MRV has not yet received Food and Drug Administration (FDA) approval for general use in the clinic; therefore, researchers continue to study virus interactions with host cells to identify circumstances where MRV effectiveness in tumor killing can be improved. In this review, we will discuss the ISR, MRV modulation of the ISR, and discuss ways in which MRV interaction with the ISR may increase the effectiveness of cancer therapeutics whose modes of action are altered by the ISR.

Tryptophan and indole metabolism in immune regulation

L-tryptophan is an essential amino acid that undergoes complex metabolic routes, resulting in production of many types of signaling molecules that fall into two types: retaining the indole ring such as serotonin, melatonin and indole-pyruvate or breaking the indole ring to form kynurenine. Kynurenines are the precursor of signaling molecules and are the first step in de novo NAD⁺ synthesis. In mammalian cells, the kynurenine pathway is initiated by the rate-limiting enzymes tryptophan-2,3-dioxygenase (TDO) and interferon responsive indoleamine 2,3-dioxygenase (IDO1) and is the major route for tryptophan catabolism. IDO1 regulates immune cell function through the kynurenine pathway but also by depleting tryptophan in microenvironments, and especially in tumors, which led to the development of IDO1 inhibitors for cancer therapy. However, the connections between tryptophan depletion versus product supply remain an ongoing challenge in cellular biochemistry and metabolism. Here, we highlight current knowledge about the physiological and pathological roles of tryptophan signaling network with a focus on the immune system.

Tissue-specific roles of GCN2 in aging and autosomal dominant retinitis pigmentosa

The organisms have the capacity to sense and adapt to their surroundings for their life in a dynamic environment. In response to amino acid starvation, cells activate a rectifying physiological program, termed the integrated stress response (ISR), to restore cellular homeostasis. General controlled non-repressed (GCN2) kinase is a master regulator of the ISR and modulates protein synthesis in response to amino acid starvation. We previously established the GCN2/ATF4/4E-BP pathway in development and aging. Here, we investigated the tissue-specific roles of GCN2 upon dietary restriction of amino acid in a Drosophila model. The knockdown of GCN2 in the gut and fat body, an energy sensing organ in Drosophila, abolished the beneficial effect of GCN2 in lifespan extension upon dietary restriction of amino acids. Proteome analysis in an autosomal dominant retinitis pigmentosa (ADRP) model showed that dietary restriction of amino acids regulates the synthesis of proteins in several pathways, including mitochondrial translation, mitochondrial gene expression, and regulation of biological quality, and that gcn2-mutant flies have reduced levels of these mitochondria-associated proteins, which may contribute to retinal degeneration in ADRP. These results indicate that the tissue-specific regulation of GCN2 contributes to normal physiology and ADRP progression.

Translational induction of ATF4 during integrated stress response requires noncanonical initiation factors eIF2D and DENR

The Integrated Stress Response (ISR) helps metazoan cells adapt to cellular stress by limiting the availability of initiator methionyl-tRNA for translation. Such limiting conditions paradoxically stimulate the translation of ATF4 mRNA through a regulatory 5' leader sequence with multiple upstream Open Reading Frames (uORFs), thereby activating stress-responsive gene expression. Here, we report the identification of two critical regulators of such ATF4 induction, the noncanonical initiation factors eIF2D and DENR. Loss of eIF2D and DENR in Drosophila results in increased vulnerability to amino acid deprivation, susceptibility to retinal degeneration caused by endoplasmic reticulum (ER) stress, and developmental defects similar to ATF4 mutants. eIF2D requires its RNA-binding motif for regulation of 5' leader-mediated ATF4 translation. Consistently, eIF2D and DENR deficient human cells show impaired ATF4 protein induction in response to ER stress. Altogether, our findings indicate that eIF2D and DENR are critical mediators of ATF4 translational induction and stress responses in vivo.

The unfolded protein response in metazoan development

Eukaryotic cells respond to an overload of unfolded proteins in the endoplasmic reticulum (ER) by activating signaling pathways that are referred to as the unfolded protein response (UPR). Much UPR research has been conducted in cultured cells that exhibit no baseline UPR activity until they are challenged by ER stress initiated by chemicals or mutant proteins. At the same time, many genes that mediate UPR signaling are essential for the development of organisms ranging from Drosophila and fish to mice and humans, indicating that there is physiological ER stress that requires UPR in normally developing animal tissues. Recent studies have elucidated the tissue-specific roles of all three branches of UPR in distinct developing tissues of Drosophila, fish and mammals. As discussed in this Review, these studies not only reveal the physiological functions of the UPR pathways but also highlight a surprising degree of specificity associated with each UPR branch in development.

The integrated stress response regulates BMP signalling through effects on translation

Background

Developmental pathways must be responsive to the environment. Phosphorylation of eIF2α enables a family of stress-sensing kinases to trigger the integrated stress response (ISR), which has pro-survival and developmental consequences. Bone morphogenetic proteins (BMPs) regulate multiple developmental processes in organisms from insects to mammals.

Results

Here we show in Drosophila that GCN2 antagonises BMP signalling through direct effects on translation and indirectly via the transcription factor crc (dATF4). Expression of a constitutively active GCN2 or loss of the eIF2α phosphatase dPPP1R15 impairs developmental BMP signalling in flies. In cells, inhibition of translation by GCN2 blocks downstream BMP signalling. Moreover, loss of d4E-BP, a target of crc, augments BMP signalling in vitro and rescues tissue development in vivo.

Conclusion

These results identify a novel mechanism by which the ISR modulates BMP signalling during development.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0503-x) contains supplementary material, which is available to authorized users.

Meeting Report - proteostasis in Ericeira

It was a sunny Ericeira, in Portugal, that received the participants of the EMBO Workshop on Proteostasis, from 17 to 21 November 2017. Most participants gave talks or presented posters concerning their most recent research results, and lively scientific discussions occurred against the backdrop of the beautiful Atlantic Ocean.Proteostasis is the portmanteau of the words protein and homeostasis, and it refers to the biological mechanisms controlling the biogenesis, folding, trafficking and degradation of proteins in cells. An imbalance in proteostasis can lead to the accumulation of misfolded proteins or excessive protein degradation, and is associated with many human diseases. A wide variety of research approaches are used to identify the mechanisms that regulate proteostasis, typically involving different model organisms (yeast, invertebrates or mammalian systems) and different methodologies (genetics, biochemistry, biophysics, structural biology, cell biology and organismal biology). Around 140 researchers in the proteostasis field met in the Hotel Vila Galé, Ericeira, Portugal for the EMBO Workshop in Proteostasis, organized by Pedro Domingos (ITQB-NOVA, Oeiras, Portugal) and Colin Adrain (IGC, Oeiras, Portugal). In this report, we attempt to review and integrate the ideas that emerged at the workshop. Owing to space restrictions, we could not cover all talks or posters and we apologize to the colleagues whose presentations could not be discussed.