Misfolding Process Research Articles

Estimation from moments measurements for amyloid depolymerisation

Estimating reaction rates and size distributions of protein polymers is an important step for understanding the mechanisms of protein misfolding and aggregation, a key feature for amyloid diseases. This study aims at setting this framework problem when the experimental measurements consist in the time-dynamics of a moment of the population (i.e. for instance the total polymerised mass, as in Thioflavin T measurements, or the second moment measured by Static Light Scattering). We propose a general methodology, and we solve the problem theoretically and numerically in the case of a depolymerising system. We then apply our method to experimental data of depolymerising oligomers, and conclude that smaller aggregates of ovPrP protein should be more stable than larger ones. This has an important biological implication, since it is commonly admitted that small oligomers constitute the most cytotoxic species during prion misfolding process.

Mitochondrially-Derived Peptides as Defense Against Amyloid Protein Misfolding

The misfolding and aggregation of proteins is the pathological hallmark of amyloid diseases including Alzheimer's disease (AD), familial amyloid polyneuropathy, and type 2 diabetes mellitus (T2DM). Insofar as the misfolding process results in the formation of pathogenic species, inhibition of misfolding is thought to be a promising approach to the prevention of the aforementioned diseases. Mitochondrial dysfunction has been implicated in many amyloid diseases suggesting an important mitochondrial role. Humanin and its derivatives are a novel class of mitochondrially-derived peptides with insulin sensitizing activity and various cytoprotective effects in AD and other disease model systems. Here we tested whether humanin can promote health in misfolding diseases by acting as a molecular chaperone that prevents amyloid misfolding. We tested whether islet amyloid polypeptide (IAPP), a peptide that misfolds and causes toxicity in T2DM, would be responsive to humanin. Using thioflavin T fluorescence we found that substoichiometric concentrations of the humanin-S14G analogue (HNG) potently inhibit the misfolding of hIAPP. As assessed by circular dichroism, HNG prevents misfolding by maintaining hIAPP in a predominantly random coil structure in solution. Unexpectedly, site-directed spin labeling of HNG in concert with electron paramagnetic resonance (EPR) revealed that HNG is capable of forming higher order complexes. Ongoing investigation into the potency of these higher order structures will test whether they participate in the inhibition of IAPP misfolding. Finally HNG appears to have biological effects including a partial attenuation of IAPP-mediated cytotoxicity and a reversal of the increase in oxygen consumption seen when INS832/13 cells, a rodent insulinoma cell line, are challenged with IAPP. In summary our studies suggest the possibility that humanin, and perhaps other mitochondrially-derived peptides, have chaperone-like properties that could reverse the pathological processes involved in the development of T2DM.

Studies on Domain Specific Aggregation Behavior of Huntingtin Exon1

The pathogenesis of Huntington's disease results from polyQ expansions (>36Q) in the Huntingtin (Htt) protein.1 These polyQ expansions make Htt less soluble and promote the formation of misfolded oligomers, fibrils and aggregates in Huntington's disease.2 Efforts to prevent aggregation will greatly benefit from a detailed molecular understanding of the misfolding process. However, htt misfolding has been difficult to study as the protein is tough to handle and examine spectroscopically. Here we developed a novel purification scheme to generate recombinant, clean and monomeric Htt exon1, an aggregation prone fragment of htt that is highly expressed in disease. The misfolding of spin labeled derivatives of Htt exon1 were then monitored by EPR in order to obtain site-specific folding information for residues in different regions of the protein. Our data indicate that residues in the N-terminal N17, the middle polyQ region and the C-terminal, proline rich region all undergo structural changes on different time scales. Moreover, we have also found that the aggregation kinetics and mechanisms of aggregation significantly depend on Q length. Overall, the data indicate distinct phases in which different regions of the molecule undergo conformational changes. Each of these stages may afford the design of different compounds intended at altering the aggregation process.1. Bates, GP.; Harper, PS.; Jones, L., editors. Huntington's Disease. Oxford University Press; Oxford, U.K.: 2002.2. Bates, GP.; Benn, C. The polyglutamine diseases. In: Bates, GP.; Harper, PS.; Jones, L., editors. Huntington's Disease. Oxford University Press; Oxford, U.K.: 2002. p. 429-472.

The role of metals in protein conformational disorders - The case of prion protein and Aβ -peptide

Protein conformational disorders are members of a vast class of pathologies in which endogenous proteins or peptides undergo a misfolding process by switching from the physiological soluble configuration to a pathological fibrillar insoluble state. An important, but not yet fully elucidated, role in the process appears to be played by transition metal ions, mainly copper and zinc. X-ray absorption spectroscopy is one of the most suitable techniques for the structural characterization of biological molecules in complex with metal. Owing to its chemical selectivity and sensitivity to the local atomic geometry around the absorber, it can be successfully used to study the environment of metal ions in complex with proteins and peptides in physiological conditions. In this paper we present X-ray absorption spectroscopy studies of the metal ions coordination modes in systems where metals are complexed with specific amyloidogenic proteins and peptides. In particular, we show results concerning the Amyloid β peptide, that is involved in Alzheimer's disease, and the Prion protein, that is responsible for the Transmissible Spongiform Encephalopathy. Our findings suggest that the copper and zinc ions may play a crucial role in the aggregation and fibril formation process of these two biomolecules. Elucidating this kind of interaction could be a key preliminary step before any viable therapy can be conceived or designed.

Enhanced Molecular Mobility of Ordinarily Structured Regions Drives Polyglutamine Disease

Polyglutamine expansion is a hallmark of nine neurodegenerative diseases, with protein aggregation intrinsically linked to disease progression. Although polyglutamine expansion accelerates protein aggregation, the misfolding process is frequently instigated by flanking domains. For example, polyglutamine expansion in ataxin-3 allosterically triggers the aggregation of the catalytic Josephin domain. The molecular mechanism that underpins this allosteric aggregation trigger remains to be determined. Here, we establish that polyglutamine expansion increases the molecular mobility of two juxtaposed helices critical to ataxin-3 deubiquitinase activity. Within one of these helices, we identified a highly amyloidogenic sequence motif that instigates aggregation and forms the core of the growing fibril. Critically, by mutating residues within this key region, we decrease local structural fluctuations to slow ataxin-3 aggregation. This provides significant insight, down to the molecular level, into how polyglutamine expansion drives aggregation and explains the positive correlation between polyglutamine tract length, protein aggregation, and disease severity.

Hsp31 Is a Stress Response Chaperone That Intervenes in the Protein Misfolding Process

The Saccharomyces cerevisiae heat shock protein Hsp31 is a stress-inducible homodimeric protein that is involved in diauxic shift reprogramming and has glyoxalase activity. We show that substoichiometric concentrations of Hsp31 can abrogate aggregation of a broad array of substrates in vitro. Hsp31 also modulates the aggregation of α-synuclein (αSyn), a target of the chaperone activity of human DJ-1, an Hsp31 homolog. We demonstrate that Hsp31 is able to suppress the in vitro fibrillization or aggregation of αSyn, citrate synthase and insulin. Chaperone activity was also observed in vivo because constitutive overexpression of Hsp31 reduced the incidence of αSyn cytoplasmic foci, and yeast cells were rescued from αSyn-generated proteotoxicity upon Hsp31 overexpression. Moreover, we showed that Hsp31 protein levels are increased by H2O2, in the diauxic phase of normal growth conditions, and in cells under αSyn-mediated proteotoxic stress. We show that Hsp31 chaperone activity and not the methylglyoxalase activity or the autophagy pathway drives the protective effects. We also demonstrate reduced aggregation of the Sup35 prion domain, PrD-Sup35, as visualized by fluorescent protein fusions. In addition, Hsp31 acts on its substrates prior to the formation of large aggregates because Hsp31 does not mutually localize with prion aggregates, and it prevents the formation of detectable in vitro αSyn fibrils. These studies establish that the protective role of Hsp31 against cellular stress is achieved by chaperone activity that intervenes early in the protein misfolding process and is effective on a wide spectrum of substrate proteins, including αSyn and prion proteins.

Solid-State Nuclear Magnetic Resonance on the Static and Dynamic Domains of Huntingtin Exon-1 Fibrils.

Amyloid-like fibrils formed by huntingtin exon-1 (htt_ex1) are a hallmark of Huntington's disease (HD). The structure of these fibrils is unknown, and determining their structure is an important step toward understanding the misfolding processes that cause HD. In HD, a polyglutamine (polyQ) domain in htt_ex1 is expanded to a degree that it gains the ability to form aggregates comprising the core of the resulting fibrils. Despite the simplicity of this polyQ sequence, the structure of htt_ex1 fibrils has been difficult to determine. This study provides a detailed structural investigation of fibrils formed by htt_ex1 using solid-state nuclear magnetic resonance (NMR) spectroscopy. We show that the polyQ domain of htt_ex1 forms the static amyloid core similar to polyQ model peptides. The Gln residues of this domain exist in two distinct conformations that are found in separate domains or monomers but are relatively close in space. The rest of htt_ex1 is relatively dynamic on an NMR time scale, especially the proline-rich C-terminus, which we found to be in a polyproline II helical and random coil conformation. We observed a similar dynamic C-terminus in a soluble form of htt_ex1, indicating that the conformation of this part of htt_ex1 is not changed upon its aggregation into an amyloid fibril. From these data, we propose a bottlebrush model for the fibrils formed by htt_ex1. In this model, the polyQ domains form the center and the proline-rich domains the bristles of the bottlebrush.

Structural characterization of toxic oligomers that are kinetically trapped during α-synuclein fibril formation

We describe the isolation and detailed structural characterization of stable toxic oligomers of α-synuclein that have accumulated during the process of amyloid formation. Our approach has allowed us to identify distinct subgroups of oligomers and to probe their molecular architectures by using cryo-electron microscopy (cryoEM) image reconstruction techniques. Although the oligomers exist in a range of sizes, with different extents and nature of β-sheet content and exposed hydrophobicity, they all possess a hollow cylindrical architecture with similarities to certain types of amyloid fibril, suggesting that the accumulation of at least some forms of amyloid oligomers is likely to be a consequence of very slow rates of rearrangement of their β-sheet structures. Our findings reveal the inherent multiplicity of the process of protein misfolding and the key role the β-sheet geometry acquired in the early stages of the self-assembly process plays in dictating the kinetic stability and the pathological nature of individual oligomeric species.

Dynamical Phase Transitions Reveal Amyloid-like States on Protein Folding Landscapes

Developing an understanding of protein misfolding processes presents a crucial challenge for unlocking the mysteries of human disease. In this article, we present our observations of β-sheet-rich misfolded states on a number of protein dynamical landscapes investigated through molecular dynamics simulation and Markov state models. We employ a nonequilibrium statistical mechanical theory to identify the glassy states in a protein’s dynamics, and we discuss the nonnative, β-sheet-rich states that play a distinct role in the slowest dynamics within seven protein folding systems. We highlight the fundamental similarity between these states and the amyloid structures responsible for many neurodegenerative diseases, and we discuss potential consequences for mechanisms of protein aggregation and intermolecular amyloid formation.

Chaperones ameliorate beta cell dysfunction associated with human islet amyloid polypeptide overexpression.

In type 2 diabetes, beta-cell dysfunction is thought to be due to several causes, one being the formation of toxic protein aggregates called islet amyloid, formed by accumulations of misfolded human islet amyloid polypeptide (hIAPP). The process of hIAPP misfolding and aggregation is one of the factors that may activate the unfolded protein response (UPR), perturbing endoplasmic reticulum (ER) homeostasis. Molecular chaperones have been described to be important in regulating ER response to ER stress. In the present work, we evaluate the role of chaperones in a stressed cellular model of hIAPP overexpression. A rat pancreatic beta-cell line expressing hIAPP exposed to thapsigargin or treated with high glucose and palmitic acid, both of which are known ER stress inducers, showed an increase in ER stress genes when compared to INS1E cells expressing rat IAPP or INS1E control cells. Treatment with molecular chaperone glucose-regulated protein 78 kDa (GRP78, also known as BiP) or protein disulfite isomerase (PDI), and chemical chaperones taurine-conjugated ursodeoxycholic acid (TUDCA) or 4-phenylbutyrate (PBA), alleviated ER stress and increased insulin secretion in hIAPP-expressing cells. Our results suggest that the overexpression of hIAPP induces a stronger response of ER stress markers. Moreover, endogenous and chemical chaperones are able to ameliorate induced ER stress and increase insulin secretion, suggesting that improving chaperone capacity can play an important role in improving beta-cell function in type 2 diabetes.

Recent and future grand challenges in protein folding, misfolding, and degradation.

Recent and future grand challenges in protein folding, misfolding, and degradation.

A molecular modeling study on full-length insulin: insight into initial events of amyloid formation

Studies on the structure and physico-chemical properties of amyloid fibrils are important with regard to a better understanding of amyloid diseases such as Alzheimer’s. Insulin is used as a protein model which is easily driven toward amyloid formation. In the present study, five sets of 15 ns molecular dynamics simulations were performed on insulin in order to observe the initial structural changes that occur in the process of amyloid formation. Potential energy, RMSD, and secondary structure percentage of sampled structures were analyzed in all experiments. Common residues that undergo the first conformational changes were detected to be S9 and V10 of the A chain, as well as G8 and S9 of the B chain. The RMSD of truncated insulin increased much more than full-length insulin to about 18 A. However, the beta-sheet structures percentage of full-length insulin, which is an indicative of amyloid formation, was higher than the truncated form in the presence of salt. This is indicative of the importance of the five residues of the B chain C-terminal in the insulin misfolding process. Overall, simulating full-length insulin under high temperature and in the presence of KCl could be used to assess amyloid formation and potential amyloid inhibitors of this protein.

Molecular Mechanisms of Misfolding of Amyloid Peptides

The current model for the development of Alzheimer's, Parkinson's, Huntington's, prion, and other neurodegenerative diseases involves protein misfolding as the early step followed by spontaneous aggregation, with specific proteins identified as the primary initiators for disease development. Therefore, elucidating the properties of the disease-prone misfolded states, understanding the mechanism of their formation, and identification of their most toxic forms will open prospects for the development of early diagnostics and specific therapeutics for these diseases. We have developed single molecule AFM force spectroscopy (SMFS) experimental approach enabling us to probe interprotein interactions and to identify those interactions that correspond to misfolded protein states. Using SMFS, we have discovered that the misfolded dimers are very stable and have a lifetime in a second time scale. Such a long lifetime of dimers suggests that the formation of dimers is the mechanism by which the protein misfolded state is stabilized. We hypothesize that the formation of highly stable misfolded dimers is a critical step in the entire process of the peptide self-assembly into aggregates. The Molecular Dynamics (MD) simulation performed at the μs timescale demonstrated that isolated non-structured monomer upon approaching to each other changed dramatically their initial conformation and formed dimers with antiparallel beta-sheet structures. Steered MD approach showed that the dimers dissociated cooperatively resulting in a sharp rupture peak corresponding to breakage of the beta-sheet structure. Altogether, the SMFS experimental study and computational analysis revealed a critical role of the interpetide interaction in the misfolding process and highlighting the key role of the dimerization in the amyloid aggregation process. Acknowledgements: Grants from NIH (5R01 GM096039-02) and NSF (EPS-1004094).

Structural Characterization and Inhibition of Toxic Amyloid-β Oligomeric Intermediates

Misfolding of amyloid-beta (Aβ) has been implicated in Alzheimer’s disease (AD). Recent studies have shown that early oligomeric intermediates formed in the misfolding pathway are the main toxic species as they kill neuronal cells. Therefore, the development of compounds to inhibit Aβ aggregation—and thus to avoid the formation of toxic oligomeric intermediates—is urgently needed as they could be potential drugs to treat AD (1). Although this has been well realized by the scientific community and many research groups have been working on developing such compounds, the main limitation has been the lack of biophysical techniques that can provide atomic-level structural insights into the misfolding process. Fortunately, NMR techniques can be utilized to obtain such high-resolution information on amyloid peptides and proteins as demonstrated by recent studies. In this context, the study by Raditsis et al. (2) demonstrates the value of solution NMR techniques in understanding the molecular basis for inhibition of oligomerization Aβ1−42 (and also a peptide fragment Aβ12−28) by the iron-transport glycoprotein transferrin that is present in plasma and cerebrospinal fluid (2). Specifically, using off-resonance relaxation and saturation transfer difference NMR experiments, they have shown that transferrin preferentially binds to Aβ oligomers and inhibits the aggregation of monomers into large oligomers. The similarity between the mechanisms of Aβ self-association inhibition by transferrin and another plasma protein human serum albumin (3) is intriguing, and indicates that the Aβ-oligomer-binding model proposed in this study could be a general strategy shared by multiple plasma proteins. In fact, to fully understand the Aβ toxicity, it is essential to solve the three-dimensional structures of early oligomers as they provide insights into molecular interactions that drive the misfolding and aggregation of Aβ. Although NMR is one of the most commonly used biophysical tools in structural biology, its poor sensitivity severely limits structural investigation of fast aggregating amyloid proteins. Increasing the amount of peptide/protein or temperature to enhance NMR sensitivity is not desirable, for it increases the rate of amyloid aggregation. In addition, the presence of heterogeneous species—monomers, oligomers, and protofibers—significantly lower the spectral resolution though only the fast-tumbling small size species are detected in solution NMR measurements. Despite these limitations, a recent NMR study determined the high-resolution structure of Aβ1-40 from solution that could be a nucleus in the aggregation process (Fig. 1 A). Remarkably, the NMR structure reveals that the hydrophobic H13–D23 region of Aβ1-40 forms a 310 helix and the unstructured hydrophobic residues of the N- and C-termini collapse against the central 310 helix (4). Though previous studies have detected the formation of a transient, on-pathway α-helical intermediate, to our knowledge this is the first experimentally determined high-resolution structure of Aβ1-40 (5). This structure is increasingly utilized in the development of compounds to inhibit the aggregation of Aβ peptides. Figure 1 (A) A partially folded structure of Aβ1-40 (PDB:2LFM) in solution determined by NMR spectroscopy (4). (B) NMR investigations for identification of interactions of Aβ with proteins, metal ions, and/or small molecules (6–9). Because large oligomers are not detected in solution NMR experiments, NMR signals detected from monomers are used to characterize Aβ-ligand and Aβ-protein interactions (6–9). Such studies have been used to develop compounds that can inhibit Aβ aggregation as well as avoid metal-induced aggregation by modulating the interaction between the metal (e.g., Cu(II) and Zn(II)) and the peptide (6,7,9) (Fig. 1 B). In fact, simple high-throughput two-dimensional NMR experiments such as NOESY, HSQC, TROSY-HSQC, or SOFAST-HMQC are increasingly utilized to: 1. Identify direct interactions (structures) of compounds with Aβ at a molecular level, which leads to a better design or optimization of molecules to efficiently suppress the formation of toxic Aβ species; and 2. Screen a chemical library against Aβ aggregation in a high-throughput manner. Recent studies have demonstrated the feasibility of real-time measurement of the aggregation of Aβ and IAPP using 19F NMR (10,11). These studies have revealed the formation of several different types of small-size Aβ oligomers, the nonexistence of appreciable nonfibrillar islet amyloid polypeptide protein intermediates, and the effect of an amyloid inhibitor epigallocatechin gallate (10,11). Due to both fundamental and translation aspects, drug discovery for multiple targets in human diseases including the misfolding proteins (amyloids) has been assisted and will continue to greatly benefit by the development and applications of NMR spectroscopy. In this context, the results reported by Raditsis et al. (2) are exciting and further demonstrate the power of simple NMR experiments to characterize protein-Aβ interactions. At the same time, it should also be realized that the investigation of the Aβ-membrane interaction and the roles of membrane components are essential to understanding the mechanism of Aβ toxicity in AD (12).

Introducing a Rigid Loop Structure from Deer into Mouse Prion Protein Increases Its Propensity for Misfolding In Vitro

Prion diseases are fatal neurodegenerative disorders characterized by misfolding of the cellular prion protein (PrPc) into the disease-associated isoform (PrPSc) that has increased β-sheet content and partial resistance to proteolytic digestion. Prion diseases from different mammalian species have varying propensities for transmission upon exposure of an uninfected host to the infectious agent. Chronic Wasting Disease (CWD) is a highly transmissible prion disease that affects free ranging and farmed populations of cervids including deer, elk and moose, as well as other mammals in experimental settings. The molecular mechanisms allowing CWD to maintain comparatively high transmission rates have not been determined. Previous work has identified a unique structural feature in cervid PrP, a rigid loop between β-sheet 2 and α-helix 2 on the surface of the protein. This study was designed to test the hypothesis that the rigid loop has a direct influence on the misfolding process. The rigid loop was introduced into murine PrP as the result of two amino acid substitutions: S170N and N174T. Wild-type and rigid loop murine PrP were expressed in E. coli and purified. Misfolding propensity was compared for the two proteins using biochemical techniques and cell free misfolding and conversion systems. Murine PrP with a rigid loop misfolded in cell free systems with greater propensity than wild type murine PrP. In a lipid-based conversion assay, rigid loop PrP converted to a PK resistant, aggregated isoform at lower concentrations than wild-type PrP. Using both proteins as substrates in real time quaking-induced conversion, rigid loop PrP adopted a misfolded isoform more readily than wild type PrP. Taken together, these findings may help explain the high transmission rates observed for CWD within cervids.

Molecular Mechanism of Misfolding and Aggregation of Aβ(13–23)

The misfolding and self-assembly of the amyloid-beta (Aβ) peptide into aggregates is a molecular signature of the development of Alzheimer's disease, but molecular mechanisms of the peptide aggregation remain unknown. Here, we combined Atomic Force Microscopy (AFM) and Molecular Dynamics (MD) simulations to characterize the misfolding process of an Aβ peptide. Dynamic force spectroscopy AFM analysis showed that the peptide forms stable dimers with a lifetime of ∼1 s. During MD simulations, isolated monomers gradually adopt essentially similar nonstructured conformations independent from the initial structure. However, when two monomers approach their structure changes dramatically, and the conformational space for the two monomers become restricted. The arrangement of monomers in antiparallel orientation leads to the cooperative formation of β-sheet conformation. Interactions, including hydrogen bonds, salt bridges, and weakly polar interactions of side chains stabilize the structure of the dimer. Under the applied force, the dimer, as during the AFM experiments, dissociates in a cooperative manner. Thus, misfolding of the Aβ peptide proceeds via the loss of conformational flexibility and formation of stable dimers suggesting their key role in the subsequent Aβ aggregation process.

Natural compounds may open new routes to treatment of amyloid diseases.

Protein misfolding disorders, such as Alzheimer's disease and Parkinson's disease, have in common that a protein accumulates in an insoluble form in the affected tissue. The process of aggregation follows a mechanism of seeded polymerization. Although the toxic species is still not well defined, the process, rather than the end product, of fibril formation is likely the main culprit in amyloid toxicity. These findings suggest that therapeutic strategies directed against the protein misfolding cascade should focus on depleting aggregation intermediates rather than on large fibrillar aggregates. Recent studies involving natural compounds have suggested new intervention strategies. The polyphenol epi-gallocatechine-3-gallate (EGCG), the main polyphenol in Camilla sinensis, binds directly to a large number of proteins that are involved in protein misfolding diseases and inhibits their fibrillization. Instead, it promotes the formation of stable, spherical aggregates. These spherical aggregates are not cytotoxic, have a lower β-sheet content than fibrils, and do not catalyze fibril formation. Correspondingly, epi-gallocatechine-3-gallate remodels amyloid fibrils into aggregates with the same properties. Derivatives of Orcein, which is a phenoxazine dye that can be isolated from the lichen Roccella tinctoria, form a second promising class of natural compounds. They accelerate fibril formation of the Alzheimer's disease-related amyloid-beta peptide. At the same time these compounds deplete oligomeric and protofibrillar forms of the peptide. These compounds may serve as proof-of-principle for the strategies of promoting and redirecting fibril formation. Both may emerge as two promising new therapeutic approaches to intervening into protein misfolding processes.

Intrabodies as neuroprotective therapeutics.

The process of misfolding of proteins that can trigger a pathogenic cascade leading to neurodegenerative diseases largely originates intracellularly. It is possible to harness the specificity and affinity of antibodies to counteract either protein misfolding itself, or the aberrant interactions and excess stressors immediately downstream of the primary insult. This review covers the emerging field of engineering intracellular antibody fragments, intrabodies and nanobodies, in neurodegeneration. Huntington's disease has provided the clearest proof of concept for this approach. The model systems and readouts for this disorder power the studies, and the potential to intervene therapeutically at early stages in known carriers with projected ages of onset increases the chances of meaningful clinical trials. Both single-chain Fv and single-domain nanobodies have been identified against specific targets; data have allowed feedback for rational design of bifunctional constructs, as well as target validation. Intrabodies that can modulate the primary accumulating protein in Parkinson's disease, alpha-synuclein, are also reviewed, covering a range of domains and conformers. Recombinant antibody technology has become a major player in the therapeutic pipeline for cancer, infectious diseases, and autoimmunity. There is also tremendous potential for applying this powerful biotechnology to neurological diseases.

Amyloid Formation in Light Chain Amyloidosis

Light chain amyloidosis is one of the unique examples within amyloid diseases where the amyloidogenic precursor is a protein that escapes the quality control machinery and is secreted from the cells to be circulated in the bloodstream. The immunoglobulin light chains are produced by an abnormally proliferative monoclonal population of plasma cells that under normal conditions produce immunoglobulin molecules such as IgG, IgM or IgA. Once the light chains are in circulation, the proteins misfold and deposit as amyloid fibrils in numerous tissues and organs, causing organ failure and death. While there is a correlation between the thermodynamic stability of the protein and the kinetics of amyloid formation, we have recently found that this correlation applies within a thermodynamic range, and it is only a helpful correlation when comparing mutants from the same protein. Light chain amyloidosis poses unique challenges because each patient has a unique protein sequence as a result of the selection of a germline gene and the incorporation of somatic mutations. The exact location of the misfolding process is unknown as well as the full characterization of all of the toxic species populated during the amyloid formation process in light chain amyloidosis.

Reactions drive conformations. Biomimetic properties and devices, theoretical description.

Life is supported by cellular reactions driving conformational, folding and unfolding macromolecular movements with ionic and aqueous exchange. Here we review the state of the art of the electrochemistry of conducting polymers as elemental material models of biological reactive gels. The different experimental methodologies allowing identification and quantification of the reaction induced molecular (conformation) and macroscopic (relaxation, swelling, shrinking and compaction) structural changes are reviewed. Similar structural effects from other materials and systems, artificial or biological, are presented. Some reaction induced properties and devices mimicking biological functions and organs are described: sensing and tactile artificial muscles, smart membranes, artificial glands or artificial chemical synapses. The new structural chemical kinetics opens the way to modelling and predicting health issues linked to reactive folding or misfolding processes, and to advancing the knowledge of brain molecular mechanisms such as memory. Chemo-electronic conformational memories and dual sensing-actuating, zoomorphic and anthropomorphic gel tools and robots are envisaged.