Granulostasis: Protein Quality Control of RNP Granules

Ribonucleoprotein (RNP) granules transport, store, or degrade messenger RNAs, thereby indirectly regulating protein synthesis. Normally, RNP granules are highly dynamic compartments. However, because of aging or severe environmental stress, RNP granules, in particular stress granules (SGs), convert into solid, aggregate-like inclusions. There is increasing evidence that such RNA-protein inclusions are associated with several age-related neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), fronto-temporal dementia (FTD) and Alzheimer's disease (AD). Thus, understanding what triggers the conversion of RNP granules into aggregates and identifying the cellular players that control RNP granules will be critical to develop treatments for these diseases. In this review article, we discuss recent insight into RNP and SG formation. More specifically, we examine the evidence for liquid-liquid phase separation (LLPS) as an organizing principle of RNP granules and the role of aggregation-prone RNA-binding proteins (RBPs) in this process. We further discuss recent findings that liquid-like SGs can sequester misfolded proteins, which promote an aberrant conversion of liquid SGs into solid aggregates. Importantly, very recent studies show that a specific protein quality control (PQC) process prevents the accumulation of misfolding-prone proteins in SGs and, by doing so, maintains the dynamic state of SGs. This quality control process has been referred to as granulostasis and it relies on the specific action of the HSPB8-BAG3-HSP70 complex. Additional players such as p97/valosin containing protein (VCP) and other molecular chaperones (e.g., HSPB1) participate, directly or indirectly, in granulostasis, and ensure the timely elimination of defective ribosomal products and other misfolded proteins from SGs. Finally, we discuss recent findings that, in the stress recovery phase, SGs are preferentially disassembled with the assistance of chaperones, and we discuss evidence for a back-up system that targets aberrant SGs to the aggresome for autophagy-mediated clearance. Altogether the findings discussed here provide evidence for an intricate network of interactions between RNP granules and various components of the PQC machinery. Molecular chaperones in particular are emerging as key players that control the composition and dynamics of RNP granules, which may be important to protect against age-related diseases

Um panorama do tema da inovação social nos três setores: uma pesquisa nos estudos das universidades gaúchas

Purpose – The Social Innovation (SI) theme is still considered new, however, in the last decades it has been treated with more importance, gaining prominence in the academic environment, and it has become an object of analysis in several researches. Thus, this paper aims to analyze the evolution of the SI theme in the academic scope of gaucho universities.Design/methodology/approach – The research has a theoretical-empirical nature, a qualitative and quantitative approach. It establishes a systematic review on SI, analyzes the objectives and results of a sample of 76 dissertations and theses produced in Rio Grande do Sul universities, through a systematic review of the literature with meta-analysis.Findings – After analyzing the data, we observed that the topic has become more widely addressed in recent years, however, there is still no single concept. It was identified that it is being used to address the most different issues related to innovations that modify a social relationship, being applied in the most different sectors or in an intersectoral way.Originality/value (mandatory) – The paper presents an overview of the research and a framework with the characteristics present in the SI initiatives in the five sectors, presenting suggestions for future studies. Demonstrate that the concept of SI will be increasingly used because it is an important theme in the construction of a transformation of local realities, either by generating income, by seeking improvements in the quality of life or by new ways of thinking about global sustainability.Objetivo – O tema Inovação Social (IS) ainda é considerado novo, porém, nas últimas décadas tem sido tratado com mais importância, ganhando destaque no meio acadêmico e tem se tornado objeto de análise em diversas pesquisas. Assim, este artigo tem como objetivo analisar a evolução da utilização do tema Inovação Social no âmbito acadêmico das universidades gaúchas.Design/metodologia/abordagem – A pesquisa tem natureza teórico-empírica, com abordagem qualitativa e quantitativa. Estabelece uma revisão sistemática sobre inovação social, analisando os objetivos e resultados de uma amostra de 76 dissertações e teses produzidas em universidades do Rio Grande do Sul, por meio de uma revisão sistemática da literatura com metanálise.Resultados – Após a análise dos dados, constatou-se que o tema passou a ser mais abordado nos últimos anos, porém, ainda não existe um conceito único para a temática. Identificou-se que está sendo utilizado para abordar as mais diversas questões relacionadas às inovações que modificam uma relação social, sendo aplicadas nos mais diversos setores ou de forma intersetorial.Originalidade – O artigo apresenta uma visão geral da pesquisa e um quadro com as características presentes nas iniciativas de SI nos cinco setores, apresentando sugestões para estudos futuros em cada uma das áreas. Demonstra que o conceito de Inovação Social será cada vez mais utilizado por ser um tema importante na construção de uma transformação das realidades locais, seja pela geração de renda, pela busca de melhorias na qualidade de vida ou por novas formas de pensar a sustentabilidade global

Estudio de la formación de aldehídos de Strecker a partir de diacetilo y de quinonas

Un exceso de oxidación en el vino puede acabar con las propiedades aromáticas y la vida del mismo. Los máximos responsables del aroma del vino oxidado son los aldehídos, como el acetaldehído o los aldehídos de Strecker (fenilacetaldehído, metional, isobutiraldehído, 3-metilbutanal y 2-metilbutanal). Estos últimos se forman en la degradación de Strecker, una reacción entre un aminoácido específico y un compuesto dicarbonílico. Los aminoácidos precursores son fenilalanina, metionina, valina, leucina e isoleucina, respectivamente. En el presente trabajo se estudia la formación de los aldehídos de Strecker a partir de dos compuestos dicarbonílicos distintos: el diacetilo y la 4-metilquinona (producto de la oxidación del 4-metilcatecol). Los análisis de aldehídos se llevaron a cabo tras una derivatización, mediante una extracción en fase sólida y posterior inyección en un cromatógrafo de gases con detector de espectrómetro de masas. Se llevaron a cabo dos experiencias siendo la matriz vino sintético. En la primera, se trabajó con disoluciones 1mM de diacetilo y cada uno de los aminoácidos correspondientes. Las muestras estuvieron 32 días a temperatura ambiente y después se analizaron. Los rendimientos de reacción varían entre 0,007-0,07%. En la segunda experiencia se trabajó con disoluciones 1mM de 4-metilcatecol y de los aminoácidos, y se añadieron metales y O2, necesarios para producir el compuesto dicarbonílico a partir del fenol. Las muestras se incubaron a 35ºC y después de 57 días se analizaron. Los rendimientos de formación de aldehídos oscilan entre el 9-40%. En ambos experimentos se observan diferencias significativas en la concentración de aldehídos de Strecker según el aminoácido utilizado, siendo cada aldehído específico de su aminoácido. La metionina fue el aminoácido más reactivo de forma significativa en ambas experiencias. An excess of wine oxidation may well diminish wine's aromatic properties and, consequently, its life. Aldehydes, like acetaldehyde as well as Strecker aldehydes (phenylacetaldehyde, methional, isobutyraldehyde, 3-methylbutanal, and 2-methylbutanal), are the major responsible of wine's oxidized flavour. The latter are formed in the Strecker degradation, when a chemical reaction between an specific amino acid and a carbonyl compound occurs. Phenylalanine, methionine, valine, leucine and isoleucine are the precursor amino acids of these aldehydes. In this study, the Strecker aldehydes' formation is promoted by using diacetyl and 4-methylquinone (oxidized product of 4-methylcatechol) as carbonyl compounds. Analysis of aldehydes was performed by using a gas chromatograph with mass spectrometer detector after their derivatization. Two experiments were set up and in both the matrix was synthetic wine. In the first one, 1mM diacetyl solution plus 1mM solutions of each amino acid were used. Samples were stored for 32 days at room temperature before their analysis. Reaction yields were among 0,007-0,07%. In the second experiment 1mM solutions of 4-methylcatechol, amino acids were used and metals and oxygen were added. Samples were incubated during 57 days and then analysed. Reaction yields were among 9-40%. Significant differences in Strecker aldehyde's concentration depending on the amino acid used were found in both experiments. Methionine was the most reactive precursor amino acid in the two of them.<br /

Proportional Cerebellum Size Predicts Fear Habituation in Chickens

The cerebellum has a highly conserved neural structure across species but varies widely in size. The wide variation in cerebellar size (both absolute and in proportion to the rest of the brain) among species and populations suggests that functional specialization is linked to its size. There is increasing recognition that the cerebellum contributes to cognitive processing and emotional control in addition to its role in motor coordination. However, to what extent cerebellum size reflects variation in these behavioral processes within species remains largely unknown. By using a unique intercross chicken population based on parental lines with high divergence in cerebellum size, we compared the behavior of individuals repeatedly exposed to the same fear test (emergence test) early in life and after sexual maturity (eight trials per age group) with proportional cerebellum size and cerebellum neural density. While proportional cerebellum size did not predict the initial fear response of the individuals (trial 1), it did increasingly predict adult individuals response as the trials progressed. Our results suggest that proportional cerebellum size does not necessarily predict an individual's fear response, but rather the habituation process to a fearful stimulus. Cerebellum neuronal density did not predict fear behavior in the individuals which suggests that these effects do not result from changes in neuronal density but due to other variables linked to proportional cerebellum size which might underlie fear habituation

An interaction study in mammalian cells demonstrates weak binding of HSPB2 to BAG3, which is regulated by HSPB3 and abrogated by HSPB8

The ten mammalian small heat shock proteins (sHSPs/HSPBs) show a different expression profile, although the majority of them are abundant in skeletal and cardiac muscles. HSPBs form hetero-oligomers and homo-oligomers by interacting together and complexes containing, e.g., HSPB2/HSPB3 or HSPB1/HSPB5 have been documented in mammalian cells and muscles. Moreover, HSPB8 associates with the Hsc70/Hsp70 co-chaperone BAG3, in mammalian, skeletal, and cardiac muscle cells. Interaction of HSPB8 with BAG3 regulates its stability and function. Weak association of HSPB5 and HSPB6 with BAG3 has been also reported upon overexpression in cells, supporting the idea that BAG3 might indirectly modulate the function of several HSPBs. However, it is yet unknown whether other HSPBs highly expressed in muscles such as HSPB2 and HSPB3 also bind to BAG3. Here, we report that in mammalian cells, upon overexpression, HSPB2 binds to BAG3 with an affinity weaker than HSPB8. HSPB2 competes with HSPB8 for binding to BAG3. In contrast, HSPB3 negatively regulates HSPB2 association with BAG3. In human myoblasts that express HSPB2, HSPB3, HSPB8, and BAG3, the latter interacts selectively with HSPB8. Combining these data, it supports the interpretation that HSPB8-BAG3 is the preferred interaction

Human Small Heat Shock Protein B8 Inhibits Protein Aggregation without Affecting the Native Folding Process

: Small Heat Shock Proteins (sHSPs) are key components of our Protein Quality Control system and are thought to act as reservoirs that neutralize irreversible protein aggregation. Yet, sHSPs can also act as sequestrases, promoting protein sequestration into aggregates, thus challenging our understanding of their exact mechanisms of action. Here, we employ optical tweezers to explore the mechanisms of action of the human small heat shock protein HSPB8 and its pathogenic mutant K141E, which is associated with neuromuscular disease. Through single-molecule manipulation experiments, we studied how HSPB8 and its K141E mutant affect the refolding and aggregation processes of the maltose binding protein. Our data show that HSPB8 selectively suppresses protein aggregation without affecting the native folding process. This anti-aggregation mechanism is distinct from previous models that rely on the stabilization of unfolded polypeptide chains or partially folded structures, as has been reported for other chaperones. Rather, it appears that HSPB8 selectively recognizes and binds to aggregated species formed at the early stages of aggregation, preventing them from growing into larger aggregated structures. Consistently, the K141E mutation specifically targets the affinity for aggregated structures without impacting native folding, and hence impairs its anti-aggregation activity

Impact of serotonin 2C receptor null mutation on physiology and behavior associated with nigrostriatal dopamine pathway function

The impact of serotonergic neurotransmission on brain dopaminergic pathways has substantial relevance to many neuropsychiatric disorders. A particularly prominent role has been ascribed to the inhibitory effects of serotonin 2C receptor (5-HT2CR) activation on physiology and behavior mediated by the mesolimbic dopaminergic pathway, particularly in the terminal region of the nucleus accumbens. The influence of this receptor subtype on functions mediated by the nigrostriatal dopaminergic pathway is less clear. Here we report that a null mutation eliminating expression of 5-HT2CRs produces marked alterations in the activity and functional output of this pathway. 5-HT2CR mutant mice displayed increased activity of substantia nigra pars compacta (SNc) dopaminergic neurons, elevated baseline extracellular dopamine concentrations in the dorsal striatum (DSt), alterations in grooming behavior, and enhanced sensitivity to the stereotypic behavioral effects of D-amphetamine and GBR 12909. These psychostimulant responses occurred in the absence of phenotypic differences in drug-induced extracellular dopamine concentration, suggesting a phenotypic alteration in behavioral responses to released dopamine. This was further suggested by enhanced behavioral responses of mutant mice to the D1 receptor agonist SKF 81297. Differences in DSt D1 or D2 receptor expression were not found, nor were differences in medium spiny neuron firing patterns or intrinsic membrane properties following dopamine stimulation. We conclude that 5-HT2CRs regulate nigrostriatal dopaminergic activity and function both at SNc dopaminergic neurons and at a locus downstream of the DSt.peer-reviewe

Isomorphism between Systems of Equivariant Singularities

AbstractIn this article isomorphisms between systems of singularities equivariant under different Lie group actions are investigated and a sufficient condition for two systems to be isomorphic is given. With this sufficiency theorem we show that the system ofO(n)-equivariant singularities in its irreducible representation on Rnis isomorphic to that of one-dimensional Z2-equivariant singularities and the system of[formula]-dimensionalO(n)-equivariant singularities is isomorphic to that ofn-dimensionalSn-equivariant singularities

Alternatively spliced exon regulates context-dependent MEF2D higher-order assembly during myogenesis

: During muscle cell differentiation, the alternatively spliced, acidic β-domain potentiates transcription of Myocyte-specific Enhancer Factor 2 (Mef2D). Sequence analysis by the FuzDrop method indicates that the β-domain can serve as an interaction element for Mef2D higher-order assembly. In accord, we observed Mef2D mobile nuclear condensates in C2C12 cells, similar to those formed through liquid-liquid phase separation. In addition, we found Mef2D solid-like aggregates in the cytosol, the presence of which correlated with higher transcriptional activity. In parallel, we observed a progress in the early phase of myotube development, and higher MyoD and desmin expression. In accord with our predictions, the formation of aggregates was promoted by rigid β-domain variants, as well as by a disordered β-domain variant, capable of switching between liquid-like and solid-like higher-order states. Along these lines, NMR and molecular dynamics simulations corroborated that the β-domain can sample both ordered and disordered interactions leading to compact and extended conformations. These results suggest that β-domain fine-tunes Mef2D higher-order assembly to the cellular context, which provides a platform for myogenic regulatory factors and the transcriptional apparatus during the developmental process

Aberrant Compartment Formation by HSPB2 Mislocalizes Lamin A and Compromises Nuclear Integrity and Function

Small heat shock proteins (HSPBs) contain intrinsically disordered regions (IDRs), but the functions of these IDRs are still unknown. Here, we report that, in mammalian cells, HSPB2 phase separates to form nuclear compartments with liquid-like properties. We show that phase separation requires the disordered C-terminal domain of HSPB2. We further demonstrate that, in differentiating myoblasts, nuclear HSPB2 compartments sequester lamin A. Increasing the nuclear concentration of HSPB2 causes the formation of aberrant nuclear compartments that mislocalize lamin A and chromatin, with detrimental consequences for nuclear function and integrity. Importantly, phase separation of HSPB2 is regulated by HSPB3, but this ability is lost in two identified HSPB3 mutants that are associated with myopathy. Our results suggest that HSPB2 phase separation is involved in reorganizing the nucleoplasm during myoblast differentiation. Furthermore, these findings support the idea that aberrant HSPB2 phase separation, due to HSPB3 loss-of-function mutations, contributes to myopathy