REVIEW | doi:10.20944/preprints202001.0376.v1
Subject: Life Sciences, Biochemistry Keywords: myelin; intrinsically disordered protein; multiple sclerosis; peripheral neuropathies; myelination; protein folding; protein-membrane interaction; protein-protein interaction
Online: 31 January 2020 (04:55:04 CET)
Myelin ensheathes selected axonal segments within the nervous system, resulting primarily in nerve impulse acceleration, as well as mechanical and trophic support for neurons. In the central and peripheral nervous systems, various proteins that contribute to the formation and stability of myelin are present, which also harbour pathophysiological roles in myelin disease. Many myelin proteins share common attributes, including small size, high hydrophobicity, multifunctionality, longevity, and intrinsic disorder. With recent advances in protein biophysical characterization and bioinformatics, it has become evident that intrinsically disordered proteins (IDPs) are abundant in myelin, and their flexible nature enables multifunctionality. Here, we review known myelin IDPs, their conservation, molecular characteristics and functions, and their disease relevance, along with open questions and speculations. We place emphasis on classifying the molecular details of IDPs in myelin and correlate these with their various functions, including susceptibility to post-translational modifications, function in protein-protein and protein-membrane interactions, as well as their role as extended entropic chains. We discuss how myelin pathology can relate to IDPs and which molecular factors are potentially involved.
ARTICLE | doi:10.20944/preprints201910.0124.v1
Subject: Biology, Other Keywords: intrinsically disordered protein; IDP; protein-protein interaction; mutual synergistic folding; coupled folding and binding; structural analysis; structure-based classification; fold recognition
Online: 11 October 2019 (04:00:32 CEST)
Intrinsically disordered proteins mediate crucial biological functions through their interactions with other proteins. Mutual synergistic folding (MSF) occurs when all interacting proteins are disordered, folding into a stable structure in the course of the complex formation. In these cases, the folding and binding processes occur in parallel, lending the resulting structures uniquely heterogeneous features. Currently there are no dedicated classification approaches that would take into account the particular biological and biophysical properties of MSF complexes. Here we present a scalable clustering-based classification scheme, built on redundancy-filtered features that describe the sequence and structure properties of the complexes, and the role of the interaction, which is directly responsible for structure formation. Using this approach, we define six major types of MSF complexes, corresponding to biologically meaningful groups. Hence, the presented method also shows that differences in binding strength, subcellular localization, and regulation are encoded in the sequence and structural properties of proteins. While current structure classification methods can also handle complex structures, we show that the developed scheme is fundamentally different, and since it takes into account defining features of MSF complexes, it serves as a better representation of structures arising through this specific interaction mode.
REVIEW | doi:10.20944/preprints202010.0510.v1
Subject: Life Sciences, Biochemistry Keywords: disease-associated mutation; IDR; intrinsically disordered region; LLPS; phase separation; PTM; Ahr; AhRR; SIM1; SIM2; Hif-2α; NPAS4; ARNT2; BMAL1; disorder prediction; LLPS prediction; cancer; HuVarBase; catGranule prediction
Online: 26 October 2020 (10:30:47 CET)
The bHLH-PAS proteins are a family of transcription factors regulating expression of a wide range of genes involved in different functions, from differentiation and development control, by oxygen and toxins sensing to circadian clock setting. In addition to the well-preserved DNA-binding bHLH and PAS domains, bHLH-PAS proteins contain long intrinsically disordered C-terminal regions, responsible for their activity regulation. Our aim was to analyse the potential connection between disordered regions of the bHLH-PAS transcription factors with posttranscriptional modifications and liquid-liquid phase separation in the context of the disease-associated missense mutations. Highly flexible disordered regions, enriched in short more ordered motives, are responsible for wide spectrum of interactions with transcriptional co-regulators. Based on our in silico analysis and taking into account fact that transcription factors functions can be modulated by posttranslational modifications and spontaneous phase separation, we assume that the location of missense mutations inducing disease states, is clearly related to sequences directly undergoing these processes or to sequences responsible for their activity regulation.
ARTICLE | doi:10.20944/preprints201911.0061.v1
Subject: Life Sciences, Molecular Biology Keywords: rett syndrome; intrinsically disordered region; phylogenetic profile analysis; post-transcriptional modification; methyl-cpg-binding protein 2; cyclin-dependent kinase-like 5; forkhead box protein g1
Online: 6 November 2019 (10:58:54 CET)
Rett syndrome (RTT), a neurodevelopmental disorder, is mainly caused by mutations in methyl CpG-binding protein 2 (MECP2), which alter the functions of domains to either bind to methylated DNA or interact with a transcriptional co-repressor complex. It has been established that alterations in cyclin-dependent kinase-like 5 (CDKL5) or forkhead box protein G1 (FOXG1) correspond to distinct neurodevelopmental disorders, given that a series of studies have indicated that RTT is also caused by alterations in either one of these genes. We tried to elucidate RTT through evolution and structure assessment of MeCP2, CDKL5, and FOXG1, by focusing on their binding partners and disordered structures. Here, we provide insight into the similarities of the FOXG1 and MECP2 binding partners evolution and function. On the other hand, we suggest that CDKL5 could be a potential candidate for a classical RTT treatment, particularly based on its disordered structure that spans after the catalytic domain to the C-terminus, which shows abundant linear motifs that can bind to molecules with divergent structures of similar affinity. Additionally, we provide insight into the relationship between disordered structure and disease.
ARTICLE | doi:10.20944/preprints202208.0531.v1
Subject: Life Sciences, Virology Keywords: Rabies; intrinsic disorder; intrinsically disordered protein; intrinsically disordered protein region; protein-protein interaction
Online: 31 August 2022 (03:47:31 CEST)
Rabies is a neurological disease that causes between 40,000 and 70,000 deaths every year. Once a rabies patient has become symptomatic, there is no effective treatment for the illness, and in unvaccinated individuals, the case-fatality rate of rabies is close to 100%. French scientists Louis Pasteur and Émile Roux developed the first vaccine for rabies in 1885. If administered before the virus reaches the brain, the modern rabies vaccine imparts long-lasting immunity to the virus and saves more than 250,000 people every year. However, the rabies virus can suppress the host’s immune response once it has entered the cells of the brain, making death likely. This study aims to make use of disorder-based proteomics and bioinformatics to determine the impact that intrinsically disordered protein regions (IDPRs) in the proteome of the rabies virus have on the infectivity and lethality of the disease. This study uses the proteome of Rabies Lyssavirus (RABV) strain Pasteur Vaccins (PV), one of the best understood strains due to its use in the first rabies vaccine, as a model. The study suggests that the high levels of intrinsic disorder in the phosphoprotein (P-protein) and nucleoprotein (N-protein) allow them to participate in creation of the Negri bodies and help this virus suppress the antiviral immune response in the host cells. Additionally, the study suggests that there is a link between disorder in the matrix (M) protein and the modulation of viral transcription. The disordered regions in the M protein have a possible role in initiating viral budding within the cell. Furthermore, we checked the prevalence of functional disorder in a set of 37 host proteins directly involved in the interaction with the RABV proteins. The hope is that these new insights will aid in the development of treatments for rabies that are effective after infection.
ARTICLE | doi:10.20944/preprints202209.0450.v1
Subject: Life Sciences, Biophysics Keywords: Heslington brain; intrinsically disordered protein; intrinsically disordered region; binding-induced folding; disorder-to-order transition
Online: 29 September 2022 (03:49:27 CEST)
Proteomic analysis revealed the preservation of many proteins in the “Heslington brain” (which is at least 2,600-year-old brain tissue uncovered within the skull excavated in 2008 from a pit in Heslington, Yorkshire, England). Five of these proteins (“main proteins”), heavy, medium, and light neurofilament proteins (NFH, NFM, and NFL), glial fibrillary acidic protein (GFAP), and myelin basic (MBP) protein are engaged in the formation non-amyloid protein aggregates, such as intermediate filaments and myelin sheath. We used a wide spectrum of bioinformatics tools to evaluate the prevalence of functional disorder in several related sets of proteins, such as “main proteins” and their 44 interactors, as well as all other protein identified in the Heslington brain. These analyses revealed that all five “main proteins”, half of their interactors and almost one third of the Heslington brain proteins are expected to be mostly disordered. Furthermore, most of the remaining proteins are expected to contain sizable disordered regions. This is in contrary the expected substantial (if not complete) elimination of the disordered proteins from the Heslington brain. Therefore, it seems that the intrinsic disorder of NFH, NFM, NFL, GFAP, and MBP, their interactors and many other proteins might play a crucial role in preserving the Heslington brain by forming tightly folded brain protein aggregates, in which different parts are glued together via the disorder-to-order transitions.
REVIEW | doi:10.20944/preprints202103.0066.v1
Subject: Biology, Anatomy & Morphology Keywords: GRAS protein, DELLA, Intrinsically Disordered Proteins, Arbuscular Mycorrhizal association, abiotic stress
Online: 2 March 2021 (10:01:42 CET)
The GAI‐RGA ‐ and ‐SCR (GRAS) proteins belong to the plant-specific transcription factor gene family and involved in several developmental processes, phytohormone and phytochrome signaling, symbiosis, stress responses etc. GRAS proteins have a conserved GRAS domain at C-terminal and hypervariable N-terminal. The C-terminal conserved domain directly affects the function of the GRAS proteins. For instance, in Arabidopsis, mutations in this domain in Slender rice 1 (SLR1) and Repressor of GA (RGA) proteins cause significant phenotypic changes. GRAS proteins have been reported in more than 30 plant species and till now it has been divided into 17 subfamilies. This review highlighted GRAS protein's importance during several biological processes in plants, structural features of GRAS proteins, their expansion and diversification in the plants, GRAS-interacting proteins complexes and their role in biological processes. We also summarized available recent research that utilized CRISPR-Cas9 technology to manipulate GRAS genes in a plant for different traits. Further, the exploitation of GRAS genes in crop improvement programs has also been discussed
ARTICLE | doi:10.20944/preprints202109.0265.v1
Subject: Life Sciences, Biophysics Keywords: poly-PR/GR; neurodegenerative disease; LLPS; p53; intrinsically disordered domains; membraneless organelles
Online: 15 September 2021 (14:43:48 CEST)
Abstract: The most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is the presence of poly-PR/GR dipeptide repeats which are encoded by the C9orf72 gene. Recently, it was shown that poly-PR/GR alters chromatin accessibility which results in stabilization and enhancement of transcriptional activity of the tumor suppressor p53 in several neurodegenerative disease models. Reduction of p53 protein levels in cell and model organisms protects against neurotoxicity of poly-PR, and partially protects against neurotoxicity of poly-GR. Here, we aimed to study the detailed molecular mechanisms how p53 contributes to poly-PR/GR mediated neurodegeneration. Using a combination of biophysical techniques such as nuclear magnetic resonance (NMR) spectroscopy, fluorescence polarization, turbidity assays and differential interference contrast (DIC) microscopy, we found that p53 physically interacts with poly-PR/GR and triggers liquid-liquid phase separation of p53. We identified p53 transactivation domain 2 (TAD2) as the main binding site for PR25/GR25 and show that binding of poly-PR/GR to p53 is mediated by a network of electrostatic and/or hydrophobic interactions. Our findings might help to understand the mechanistic role of p53 in poly-PR/GR - associated neurodegeneration.
ARTICLE | doi:10.20944/preprints202104.0048.v1
Subject: Life Sciences, Biochemistry Keywords: Calvin-Benson-Bassham cycle; Conditionally disordered protein; Intrinsically disordered protein; photosynthesis regulation.
Online: 2 April 2021 (11:23:04 CEST)
In the chloroplast, Calvin-Benson-Bassham enzymes are active in the reducing environment imposed in the light via the electrons from the photosystems. In the dark these enzymes are inhibited, and this regulation is mainly mediated via oxidation of key regulatory cysteine residues. CP12 is a small protein that plays a role in this regulation with four cysteine residues that undergo a redox transition. Using amide-proton exchange with solvent measured by nuclear magnetic resonance (NMR) and mass-spectrometry, we confirmed that reduced CP12 is intrinsically disordered. Using real-time NMR, we showed that the oxidation of the two disulfide bridges are simultaneous. In oxidized CP12, the C23-C31 pair is in a region that undergoes a conformational exchange in the NMR-intermediate timescale. The C66-C75 pair is in the C-terminus that folds into a stable helical turn. We confirmed that these structural states exist in a physiologically relevant environment that is, in cell extract from Chlamydomonas reinhardtii. Consistent with these structural equilibria, the reduction is slower for the C66-C75 pair compared to the C23-C31 pair. Finally, the redox mid-potentials for the two cysteine pairs differ and are similar to those found for phosphoribulokinase and glyceraldehyde 3-phosphate dehydrogenase, that we relate to the regulatory role of CP12.
REVIEW | doi:10.20944/preprints201705.0129.v1
Subject: Life Sciences, Biophysics Keywords: cell fate decision; cancer attractors; gene network dynamics; EMT; drug resistance; intrinsically disordered proteins
Online: 17 May 2017 (06:25:17 CEST)
Waddington’s epigenetic landscape, a famous metaphor in developmental biology, depicts how a stem cell progresses from an undifferentiated phenotype to a differentiated one. The concept of “landscape” in the context of dynamical system theory represents a high-dimensional cell state space, in which each cell phenotype is considered as an “attractor” that is determined by interactions among multiple variables (molecular players), and is buffered against environmental fluctuations. Further, biological noise is thought to play an important role during these cell-fate decisions and in fact controls transitions between different phenotypes. Here, we discuss these phenotypic transitions in cancer from a dynamical systems perspective and invoke the concept of “cancer attractors” – hidden stable states of the underlying regulatory network that are not occupied by normal cells. Using epithelial-to-mesenchymal transition (EMT), cancer stem-like properties, metabolic reprogramming and the emergence of drug/hormone resistance as examples, we illustrate how phenotypic plasticity in cancer cells enables them to acquire hybrid phenotypes (such as hybrid epithelial/mesenchymal and hybrid metabolic phenotypes) that tend to be more aggressive and notoriously resilient to drug/hormone treatment. Furthermore, we highlight multiple factors that may give rise to phenotypic plasticity in cancer cells, such as (a) multi-stability or oscillatory behaviors governed by underlying regulatory networks involved in cell-fate decisions in cancer cells, and (b) network rewiring due to conformational dynamics of intrinsically disordered proteins (IDPs) that are highly enriched in cancer cells. We conclude by discussing why a therapeutic approach that promotes ‘recanalization’, i.e. the exit from “cancer attractors” and re-entry into “normal attractors”, is more likely to succeed rather than a conventional approach that targets individual molecules/pathways.
REVIEW | doi:10.20944/preprints202101.0026.v1
Subject: Life Sciences, Biochemistry Keywords: 20S proteasome; protein degradation; intrinsically disordered proteins; enzyme functional cycle; peptides; peptidome; proteome; oxidative stress
Online: 4 January 2021 (12:16:42 CET)
Four decades of proteasome research have yielded extensive information on ubiquitin-dependent proteolysis. The archetype of proteasomes is a 20S barrel-shaped complex that does not rely on ubiquitin as a degradation signal but can degrade substrates with a considerable unstructured stretch. Since roughly half of all proteasomes in most eukaryotic cells are free 20S complexes, ubiquitin-independent protein degradation may coexist with ubiquitin-dependent degradation by the highly regulated 26S proteasome. This article reviews recent advances in our understanding of the biochemical and structural features that underlie the proteolytic mechanism of 20S proteasomes. The two outer α-rings of 20S proteasomes provide a number of potential docking sites for loosely folded polypeptides. The binding of a substrate can induce asymmetric conformational changes, trigger gate opening, and initiate its own degradation through a protease-driven translocation mechanism. Consequently, the substrate translocates through two additional narrow apertures augmented by the β-catalytic active sites. The overall pulling force through the two annuli results in a protease-like unfolding of the substrate and subsequent proteolysis in the catalytic chamber. Although both proteasomes contain identical β-catalytic active sites, the differential translocation mechanisms yield distinct peptide products. Non-overlapping substrate repertoires and product outcomes rationalize cohabitation of both proteasome complexes in cells.
ARTICLE | doi:10.20944/preprints201905.0278.v1
Subject: Medicine & Pharmacology, Ophthalmology Keywords: NMDA; excitotoxicity; Glaucoma; melanopsin-RGCs; intrinsically photosensitive-RGCs; Brn3a+RGCs; adult albino rat; retina; SD-OCT
Online: 23 May 2019 (04:43:45 CEST)
We studied short- and long-term effects of intravitreal injection of N-methyl-D-aspartate (NMDA) on melanopsin-containing (m+) and non-melanopsin-containing (Brn3a+) retinal ganglion cells (RGCs). In adult SD-rats, the left eye received a single intravitreal injection of 5µL of 100nM NMDA. At 3 and 15 months, retinal thickness was measured in vivo using SD-OCT. Ex vivo analyses were done at 3, 7, 14 days or 15 months after damage. Whole-mounted retinas were immunolabelled for Brn3a and melanopsin, the total number of Brn3a+RGCs and m+RGCs were quantified and their topography represented. In control retinas, the mean total numbers of Brn3a+RGCs and m+RGCs were 78,903±3,572 and 2,358±144 (mean ± SD; n=10), respectively. In the NMDA injected retinas, Brn3a+RGCs numbers diminished to 50% and 25%, at 3 and 14 days, respectively, but there was no further loss up to 15 months. The number of immunoidentified m+RGCs decreased significantly at 3 days, recovered between 3-7 days and was back to normal thereafter. OCT measurements revealed a significant thinning of the left retinas at 3 and 15 months. Intravitreal injections of NMDA induce a rapid loss of 75% of Brn3a+RGCs, a transient downregulation of melanopsin expression but not m+RGC death, and a thinning of the inner retinal layers.
ARTICLE | doi:10.20944/preprints201708.0011.v1
Subject: Engineering, Mechanical Engineering Keywords: intrinsically conductive polymers; piezoresistance; polyaniline; sensing array; orthopaedic joint implants; reverse total shoulder arthroplasty; conjugated polymers
Online: 3 August 2017 (12:40:16 CEST)
Load transfer through orthopaedic joint implants is poorly understood. The longer-term outcomes of these implants are just starting to be studied, making it imperative to monitor contact loads across the entire joint implant interface to elucidate the force transmission and distribution mechanisms exhibited by these implants in service. This study proposes and demonstrates the design, implementation, and characterization of a 3D-printed smart polymer sensor array using conductive polyaniline (PANI) structures embedded within a polymeric parent phase. The piezoresistive characteristics of PANI were studied to characterize the sensing behaviours inherent to these embedded pressure sensor arrays. PANI's stable response to a continuous load, its stability throughout loading and unloading cycles, and its repeatable and linear response to incremental loading cycles together with the accuracy of these measurements were investigated. It is demonstrated that this specially developed multi-material additive manufacturing process for polyaniline is an attractive approach for the fabrication of implant components having embedded smart-polymer sensors for the measurement and analysis of joint loads in orthopaedic implants.
Subject: Biology, Other Keywords: Mediator: stress; MCHM; Med15; Snf1; polyQ; protein chaperone; master variator; intrinsically disordered regions; yeast; hydrotrope; transcription factors; Myc tag; inorganic phosphate
Online: 3 February 2020 (13:37:07 CET)
The Mediator is composed of multiple subunits conserved from yeast to humans and plays a central role in transcription. The tail components are not required for basal transcription but are required for response to different stresses. While some stresses are familiar such as heat, desiccation, and starvation, others are exotic, yet yeast can elicit a successful stress response. MCHM is a hydrotrope that induces growth arrest in yeast. We found that a naturally occurring variation in the Med15 allele, a component of the Mediator tail, altered the stress response to many chemicals in addition to MCHM. Med15 contains two polyglutamine repeats (polyQ) of variable lengths that change the gene expression of diverse pathways. Med15 protein existed in multiple isoforms and its stability was dependent on Ydj1, a protein chaperone. The protein level of the Med15 with longer polyQ tracts was lower and turned over faster than the allele with shorter polyQ repeats. MCHM sensitivity via variation of Med15 was regulated by Snf1 in a Myc tag dependent manner. Tagging Med15 with Myc altered its function in response to stress. Genetic variation in transcriptional regulators magnifies genetic differences in response to environmental changes. These polymorphic control genes are master variators.
ARTICLE | doi:10.20944/preprints201907.0013.v1
Subject: Life Sciences, Other Keywords: Rett Syndrome; intrinsically disordered region; phylogenetic profile analysis; post-transcriptional modification; methyl-CpG-binding protein 2; cyclin-dependent kinase-like 5; forkhead box protein G1
Online: 1 July 2019 (11:59:56 CEST)
Rett syndrome (RTT) is mainly caused by mutations in methyl CpG-binding protein 2, cyclin-dependent kinase-like 5, or forkhead box protein G1. These RTT-causing proteins harbor an intrinsically disordered region (IDR) whose conformation exhibits spatiotemporal heterogeneity, which not only confer versatility to the protein, but also implicates them in diseases. The IDR generally evolves more rapidly than an ordered structure. In this study, we examined the relationship between pathogenic RTT-associated point mutations in RTT-causing proteins and the evolutionary dynamics of sequence features including structural order–disorder, phosphorylation sites, and evolutionary rates. We also analyzed the molecular properties and evolution of proteins that interact with RTT-causing proteins in terms of phylogenetic profiles, tissue specificity, subcellular localization, expression level, and functions. The results indicate that constrained IDRs may function by forming contacts with other regions in the protein sequence causing pathogenic missense mutations likely to arise in the rapidly evolving IDR and affect molecular networks, leading to disease. The results also provide novel insights into the genetic basis for RTT and the evolution of the neocortex in higher vertebrates.