Sara Linse

• Lund University

The aggregation of tau into amyloid fibrils is associated with Alzheimer's disease (AD) and related tauopathies. Since different tauopathies are characterised by the formation of distinct tau fibril morphologies, it is important to combine the search of tau aggregation inhibitors with the development of in vitro tau aggregation assays that recapitu...

In this perspective, we ask the question whether the apparently lower solubility of specific proteins in amyloid disease is a cause or consequence of the protein deposition seen in such diseases. We focus on Alzheimer’s disease and start by reviewing the experimental evidence of disease-associated reduction in the measured concentration of amyloid...

α-Synuclein (αSyn) is a neuronal protein predominantly found in the brain, whose native function seems to be associated with vesicle trafficking. While intrinsically disordered in solution, the first ca. 100 residues adopt an amphipathic α-helical structure when the protein adsorbs onto membranes. Additionally, the aggregation of αSyn into highly o...

Amyloids are elongated supramolecular protein self-assemblies. Their formation is a non-covalent assembly process and as such is fully reversible. Amyloid formation is associated with several neurodegenerative diseases, and the reversibility is key to maintaining the healthy state. Reversibility is also key to the performance of fibril-based biomat...

The onset and development of Alzheimer’s disease is linked to the accumulation of pathological aggregates formed from the normally monomeric amyloid-β peptide within the central nervous system. These Aβ aggregates are increasingly successfully targeted with clinical therapies at later stages of the disease, but the fundamental molecular steps in ea...

We have investigated the adsorption of the amyloid-forming protein α-Synuclein (αSyn) onto small unilamellar vesicles composed of a mixture of zwitterionic POPC and anionic POPS lipids. αSyn monomers adsorb onto...

a-synuclein is a neuronal protein implicated in neurotransmitter release. Its function is thought to critically depend on the dynamic equilibrium between its free and its membrane-bound state. a-synuclein amyloid formation, implicated in Parkinson’s disease, is also modulated by lipid membranes. The interplay between these processes remains elusive...

A peptide corresponding to a 13-residue segment of the human protein semenogelin I has been shown to generate a hydrogel consisting of amyloid-like fibrils. The relative chemical diversity (compared to synthetic de novo sequences) with 11 distinct amino acids makes this peptide (P0) an ideal candidate for investigating the role of individual residu...

The self-assembly of amyloid-β peptide (Aβ) into fibrils and oligomers is linked to Alzheimer's disease (AD). Fibrillar aggregates in AD patient's brains contain several post-translational modifications, including phosphorylation at positions 8 and 26. These play a key role in modifying the aggregation propensity of Aβ, yet how they affect the mech...

The aggregation of Aβ42 into misfolded oligomers is a central event in the pathogenesis of Alzheimer's disease. In this study, we aimed to develop a robust experimental system that recapitulates Aβ42 oligomerization in living cells to gain insight into their neurotoxicity and to provide a platform to characterize the effects of inhibitors of this p...

Oligomeric species arising during the aggregation of α-synuclein are implicated as a major source of toxicity in Parkinson’s disease, and thus a major potential drug target. However, both their mechanism of formation and role in aggregation are largely unresolved. Here we show that, at physiological pH and in the absence of lipid membranes, α-synuc...

Functional amyloids formed by the protein FapC in Pseudomonas bacteria are key structural components of Pseudomonas biofilms, which mediate chronic infections and also contribute to antimicrobial resistance. Here, we combine...

Shear forces affect self-assembly processes ranging from crystallization to fiber formation. Here, the effect of mild agitation on amyloid fibril formation was explored for four peptides and investigated in detail for A β 42, which is associated with Alzheimer’s disease. To gain mechanistic insights into the effect of mild agitation, nonseeded and...

Oligomeric assemblies consisting of only a few protein subunits are key species in the cytotoxicity of neurodegenerative disorders, such as Alzheimer’s and Parkinson’s diseases. Their lifetime in solution and abundance, governed by the balance of their sources and sinks, are thus important determinants of disease. While significant advances have be...

Protein aggregation is a key process in the development of many neurodegenerative disorders, including dementias such as Alzheimer's disease. Significant progress has been made in understanding the molecular mechanisms of aggregate formation in pure buffer systems, much of which was enabled by the development of integrated rate laws that allowed fo...

Amyloid fibrils have been implicated in the pathogenesis of several neurodegenerative diseases, the most prevalent example being Alzheimer's disease (AD). Despite the prevalence of AD, relatively little is known about...

α-synuclein is a neuronal protein implicated in neurotransmitter release. Its function is thought to critically depend on the dynamic equilibrium between free and membrane-bound protein. α-synuclein amyloid formation implicated in Parkinson's Disease was also shown to be modulated by lipid membranes. However, it remains elusive whether α-synuclein-...

The central hallmark of Parkinson's disease pathology is the aggregation of the α-synuclein protein, which, in its healthy form, is associated with lipid membranes. Purified monomeric α-synuclein is relatively stable in vitro, but its aggregation can be triggered by the presence of lipid vesicles. Despite this central importance of lipids in the co...

For many chaperones, a propensity to self-assemble correlates with function. The highly efficient amyloid suppressing chaperone DNAJB6b has been reported to oligomerize. A key question is whether the DNAJB6b self-assemblies or their subunits are active units in the suppression of amyloid formation. Here, we address this question using a nonmodified...

The presence of amyloid fibrils is a hallmark of several neurodegenerative diseases. Some amyloidogenic proteins, such as α-synuclein and amyloid β, can interact with lipids, and this interaction can strongly...

α-synuclein is a small neuronal protein enriched at presynaptic termini. It is hypothesized to play a role in neuro-transmitter release and synaptic vesicle cycling, while the formation of α-synuclein amyloid fibrils is associated with several neurodegenerative diseases, most notably Parkinson's Disease. The molecular mechanisms of both the physiol...

Oligomeric assemblies of the amyloid β peptide (Aβ) have been investigated for over two decades as possible neurotoxic agents in Alzheimer’s disease. However, due to their heterogeneous and transient nature, it is not yet fully established which of the structural features of these oligomers may generate cellular damage. Here, we study distinct olig...

Self-replication of amyloid fibrils via secondary nucleation is an intriguing physicochemical phenomenon in which existing fibrils catalyze the formation of their own copies. The molecular events behind this fibril surface-mediated process remain largely inaccessible to current structural and imaging techniques. Using statistical mechanics, compute...

The onset and development of Alzheimer’s disease (AD) is linked to the accumulation of pathological aggregates formed from the normally monomeric amyloid-β peptide within the central nervous system. These Aβ aggregates are increasingly successfully targeted with clinical therapies, but the fundamental molecular steps that trigger the initial nuclea...

Amyloid β peptide (Aβ) is the crucial protein component of extracellular plaques in Alzheimer’s disease. The plaques also contain gangliosides lipids, which are abundant in membranes of neuronal cells and in cell-derived vesicles and exosomes. When present at concentrations above its critical micelle concentration (cmc), gangliosides can occur as m...

Aquaporin-0 (AQP0) is the main water channel in the mammalian lens and is involved in accommodation and maintaining lens transparency. AQP0 binds the Ca2+-sensing protein calmodulin (CaM) and this interaction is believed to gate its water permeability by closing the water-conducting pore. Here we express recombinant and functional human AQP0 in P....

The DNAJB6 chaperone inhibits fibril formation of aggregation-prone client peptides through interaction with aggregated and oligomeric forms of the amyloid peptides. Here, we studied the role of its C-terminal domain (CTD) using constructs comprising either the entire CTD or the first two or all four of the CTD β-strands grafted onto a scaffold pro...

The double nucleation mechanism of amyloid β (Aβ) peptide aggregation is retained from buffer to cerebrospinal fluid (CSF) but with reduced rate of all microscopic processes. Here, we used a bottom-up approach to identify retarding factors in CSF. We investigated the Aβ42 fibril formation as a function of time in the absence and presence of apolipo...

Photo-induced cross-linking of unmodified proteins (PICUP) has been used in the past to study size distributions of protein assemblies. PICUP may, for example, overcome the significant experimental challenges related to the transient nature, heterogeneity, and low concentration of amyloid protein oligomers relative to monomeric and fibrillar specie...

The human chaperone DNAJB6b increases the solubility of proteins involved in protein aggregation diseases and suppresses the nucleation of amyloid structures. Due to such favourable properties, DNAJB6b has gained increasing attention over the past decade. The understanding of how DNAJB6b operates on a molecular level may aid the design of inhibitor...

The aggregation of the protein tau into amyloid fibrils is associated with Alzheimer’s disease and related tauopathies. Since different tauopathies are characterised by the formation of distinct tau fibril polymorphs, it is important to develop in vitro tau aggregation assays that recapitulate the mechanism of tau aggregation in the brain, resultin...

Self-replication of amyloid fibrils via secondary nucleation is an intriguing physicochemical phenomenon in which existing fibrils catalyse the formation of their own copies. The molecular events behind this fibril surface-mediated process remain largely inaccessible to current structural and imaging techniques. Using statistical mechanics, compute...

Alzheimer's disease is a neurodegenerative condition which involves heavy neuronal cell death linked to oligomers formed during the aggregation process of the amyloid β peptide 42 (Aβ42). The aggregation of Aβ42 involves both primary and secondary nucleation. Secondary nucleation dominates the generation of oligomers and involves the formation of n...

A general discovery in protein science in the past few decades has been the finding that a number of unrelated proteins and peptides all have a marked propensity to form amyloid fibrils in vivo and in vitro. These structures have become known as the pathological hallmark of some of the most prevalent neurodegenerative diseases. More recently, the p...

Oligomeric species arising during aggregation of α-synuclein are proposed to be a major source of toxicity in Parkinson’s disease, and thus a major potential drug target. However, their mechanism of formation and role in aggregation are largely unresolved. Here we first show that, at physiological pH, α-synuclein aggregates by secondary nucleation,...

Amyloid fibrils may adopt different morphologies depending on the solution conditions and the protein sequence. Here, we show that two chemically identical but morphologically distinct α-synuclein fibrils can form under identical conditions. This was observed by nuclear magnetic resonance (NMR), circular dichroism (CD), and fluorescence spectroscop...

The presence of amyloid fibrils is a hallmark of several neurodegenerative diseases. Some amyloidogenic proteins, such as α-synuclein and amyloid β, can interact with lipids, and this interaction can strongly favor the formation of amyloid fibrils. In particular the primary nucleation step, i.e. the de novo formation of amyloid fibrils, has been sh...

The aggregation of the amyloid β (Aβ) peptide is one of the molecular hallmarks of Alzheimer's disease (AD). Although Aβ deposits have mostly been observed extracellularly, various studies have also reported the presence of intracellular Aβ assemblies. Because these intracellular Aβ aggregates might play a role in the onset and progression of AD, i...

Interactions of lipid vesicles play important roles in a large variety of functions and dysfunctions in the human body. Vital for several biochemical functions is the interaction between monomeric proteins and lipid membranes, and the induced phenomena such as fusion between vesicles and cell membranes, lipid exchange between the membranes, or vesi...

The self-assembly of the amyloid β 42 (Aβ42) peptide is linked to Alzheimer's disease, and oligomeric intermediates are linked to neuronal cell death during the pathology of the disease. These oligomers are produced prolifically during secondary nucleation, by which the aggregation of monomers is catalyzed on fibril surfaces. Significant progress h...

The presence of amyloid fibrils of α-synuclein is closely associated with Parkinson's disease and related synucleinopathies. It is still very challenging, however, to systematically discover small molecules that prevent the formation of these aberrant aggregates. Here, we describe a structure-based approach to identify small molecules that specific...

Parkinson's disease is characterized by the aggregation of the presynaptic protein α-synuclein (αSyn), and its co-assembly with lipids and other cellular matter in the brain. Here we investigated lipid-protein co-assembly in a system composed of αSyn and model membranes containing the glycolipid ganglioside GM3. We quantified the uptake of lipids i...

Amyloid formation is linked to devastating neurodegenerative diseases, motivating detailed studies of the mechanisms of amyloid formation. For Aβ, the peptide associated with Alzheimer’s disease, the mechanism and rate of aggregation have been established for a range of variants and conditions in vitro and in bodily fluids. A key outstanding questi...

Fibrillar protein aggregates are a hallmark of a range of human disorders, from prion diseases to dementias, but are also encountered in several functional contexts. Yet, the fundamental links between protein assembly mechanisms and their functional or pathological roles have remained elusive. Here, we analyze the aggregation kinetics of a large se...

α-Synuclein (aSyn) is a 140 residue long protein present in presynaptic termini of nerve cells. The protein is associated with Parkinson's disease, in which case it has been found to self-assemble into long amyloid fibrils forming intracellular inclusions that are also rich in lipids. Furthermore, its synaptic function is proposed to involve intera...

In vivo, apolipoprotein A-I (ApoA-I) is commonly found together with lipids in so-called lipoprotein particles. The protein has also been associated with several diseases—such as atherosclerosis and amyloidosis—where insoluble aggregates containing ApoA-I are deposited in various organs or arteries. The deposited ApoA-I has been found in the form o...

α-Synuclein is a small neuronal protein that reversibly associates with lipid membranes. The membrane interactions are believed to be central to the healthy function of this protein involved in synaptic plasticity and neurotransmitter release. α-Synuclein has been speculated to induce vesicle fusion as well as fission, processes which are analogous...

Fibrillar protein aggregates are a hallmark of the pathology of a range of human disorders, from prion diseases to dementias. Yet, the same aggregated structures that are formed in disease are also encountered in several functional contexts. The fundamental properties that determine whether these protein assembly processes are functional or, by con...

Significance Alzheimer’s disease affects a growing number of people, but a cure is lacking. The disease is connected to the formation of plaques in the brain, the first of which appear years before the first symptoms. Current approaches fail to stop or revert the propagation of these plaques, which are also a source of neurotoxic species in the for...

The aggregation of the amyloid β peptide (Aβ) is one of the major molecular hallmarks of Alzheimer′s disease. Although Aβ deposits have been mostly observed extracellularly, various studies have reported the presence of also intracellular Aβ assemblies. Because these intracellular Aβ aggregates might play a role in the onset and progression of Alzh...

The pathology of Alzheimer's disease is connected to the aggregation of β-amyloid (Aβ) peptide, which in vivo exists as a number of length-variants. Truncations and extensions are found at both the N- and C-termini, relative to the most commonly studied 40- and 42-residue alloforms. Here, we investigate the aggregation of two physiologically abunda...

Fluorescence-based single molecule techniques provide important tools towards understanding the molecular mechanism of complex neurodegenerative diseases. This requires efficient covalent attachment of fluorophores. Here we create a series of cysteine mutants (S8C, Y10C, S26C, V40C, and A42C) of Aβ42, involved in Alzheimer’s disease, based on expos...

The chaperone DNAJB6b delays amyloid formation by suppressing the nucleation of amyloid fibrils and increases the solubility of amyloid-prone proteins. These dual effects on kinetics and equilibrium are related to the unusually high chemical potential of DNAJB6b in solution. As a consequence, the chaperone alone forms highly polydisperse oligomers,...

Significance Amyloid-β (Aβ) is the subject of intense scrutiny because of its close association with Alzheimer’s disease (AD), which currently afflicts about 50 million people worldwide. The results reported in this manuscript focus on the new possibilities provided by ultrafast magic-angle spinning (MAS) ¹ H detection and fast-MAS dynamic nuclear...

The presence of amyloid fibrils of alpha-synuclein is closely associated with Parkinson's disease and related synucleinopathies. It is still very challenging, however, to systematically discover small molecules that prevent the formation of these aberrant aggregates. Here, we describe a structure-based approach to identify small molecules that spec...

Significance Alzheimeŕs disease is one of the major global health challenges. Neuronal cell dysfunction and death are connected to the self-assembly of the amyloid β peptide (Aβ42) into oligomeric and fibrillar aggregates. The fibril surface can catalyze the formation of toxic oligomers via secondary nucleation. Access to a high-resolution structur...

The self-assembly of the protein tau into neurofibrillary tangles is one of the hallmarks of Alzheimer’s disease and related tauopathies. Still, the molecular mechanism of tau aggregation is largely unknown. This problem may be addressed by systematically obtaining reproducible in vitro kinetics measurements under quiescent conditions in the absenc...

The aggregation of the human islet amyloid polypeptide (IAPP) is associated with diabetes type II. A quantitative understanding of this connection at the molecular level requires that the aggregation mechanism of IAPP is resolved in terms of the underlying microscopic steps. Here we have systematically studied recombinant IAPP, with amidated C-term...

Aggregated α-synuclein (α-syn) is the main constituent of Lewy bodies, which are a pathological hallmark of Parkinson’s disease (PD). Environmental factors are thought to be potential triggers capable of initiating the aggregation of the otherwise monomeric α-syn. Braak’s seminal work redirected attention to the intestine and recent reports of dysb...

The dense accumulation of α-Synuclein fibrils in neurons is considered to be strongly associated with Parkinson’s disease. These intracellular inclusions, called Lewy bodies, also contain significant amounts of lipids. To better understand such accumulations, it should be important to study α-Synuclein fibril formation under conditions where the fi...

Several devastating human diseases are linked to peptide self-assembly, but our understanding their onset and progression is not settled. This is a sign of the complexity of the aggregation process, which is prevented, catalyzed, or retarded by numerous factors in body fluids and cells, varying in time and space. Biophysical studies of pure peptide...

In this work we measured, by using a direct approach, the equilibrium solubility of recombinant Aβ40 peptide to be S = 0.36 ± 0.15 μM in aqueous solution of 20 mM sodium phosphate buffer at pH 7.4. Microfluidic diffusional sizing (MDS) and mass spectrometry (MALDI-TOF/TOF) with isotope standard were used to quantify the concentration of soluble Aβ4...

Thermodynamics of co-aggregation and disaggregation. ( a ) Free energy diagram for a closed system of an amyloid peptide (blue) and chaperone (red). At the highest level i, all species are monomeric. At level ii, the peptide is monomeric and the chaperone a mixture of monomers and oligomers. At level iii, there are amyloid fibrils, chaperone oligom...

Apolipoprotein A-I (ApoA-I) is the major protein constituent of high-density lipoprotein particles, and as such is involved in cholesterol transport and activation of LCAT (the lecithin:cholesterol acyltransferase). It may also form amyloidal deposits in the body, showing the multifaceted interactions of ApoA-I. In order to facilitate the study of...

Cooperative binding is a key feature of metabolic pathways, signaling, and transport processes. It provides tight regulation over a narrow concentration interval of a ligand, thus enabling switching to be triggered by small concentration variations. The data presented in this work reveal strong positive cooperativity of α-synuclein binding to phosp...

Peptides and proteins have evolved to self‐assemble into supramolecular entities through a set of non‐covalent interactions. Such structures and materials provide the functional basis of life. Crucially, biomolecular assembly processes can be highly sensitive to and modulated by environmental conditions, including temperature, light, ionic strength...

Electrostatic interactions play crucial roles in protein function. Measuring pKa value perturbations upon complex formation or self-assembly of e.g. amyloid fibrils gives valuable information about the effect of electrostatic interactions in those processes. Site-specific pKa value determination by solution NMR spectroscopy is challenged by the hig...

Calmodulin (CaM) is a ubiquitous Ca²⁺ sensing protein that binds to and modulates numerous target proteins and enzymes during cellular signaling processes. A large number of CaM-target complexes have been identified and structurally characterized, revealing a wide diversity of CaM-binding modes. A newly identified target is creatine kinase (CK), a...

The self-assembly of the protein tau into neurofibrillary tangles is one of the hallmarks of Alzheimer’s disease and related tauopathies. Still, the molecular mechanism of tau aggregation is largely unknown. This problem may be addressed by systematically obtaining reproducible in vitro kinetic measurements under quiescent conditions in the absence...

Aggregated alpha-synuclein (α-syn) is the main constituent of Lewy bodies, the main pathological hallmark of Parkinson's disease (PD). Environmental factors are thought to be potential triggers capable of initiating the aggregation of the otherwise monomeric α-syn. Braak's seminal work redirected attention to the intestine and recent reports of dys...

α-Synuclein is a membrane-interacting protein involved in Parkinson’s disease. Here we have investigated the co-association of α-synuclein and lipids from ganglioside-containing model membranes. Our study relies on the reported importance of ganglioside lipids, which are found in high amounts in neurons and exosomes, on cell-to-cell prion-like tran...

A Correction to this paper has been published: https://doi.org/10.1038/s42003-021-01680-7

Aberrant soluble oligomers formed by the amyloid-β peptide (Aβ) are major pathogenic agents in the onset and progression of Alzheimer’s disease. A variety of biomolecules can influence the formation of these oligomers in the brain, although their mechanisms of action are still largely unknown. Here, we studied the effects on Aβ aggregation of DOPAL...

The aggregation of α-synuclein is a central event in Parkinsons’s disease and related synucleinopathies. Since pharmacologically targeting this process, however, has not yet resulted in approved disease-modifying treatments, there is an unmet need of developing novel methods of drug discovery. In this context, the use of chemical kinetics has recen...

The amyloid cascade hypothesis, according to which the self-assembly of amyloid-β peptide (Aβ) is a causative process in Alzheimer’s disease, has driven many therapeutic efforts for the past 20 years. Failures of clinical trials investigating Aβ-targeted therapies have been interpreted as evidence against this hypothesis, irrespective of the charac...

Protein folding is governed by non-covalent interactions under the benefits and constraints of the covalent linkage of the backbone chain. In the current work we investigate the influence of loop length variation on the free energies of folding and ligand binding in a small globular single-domain protein containing two EF-hand subdomains—calbindin...

Self-assembling peptide-based hydrogels are a class of tunable soft materials that have been shown to be highly useful for a number of biomedical applications. The dynamic formation of the supramolecular fibrils that compose these materials has heretofore remained poorly characterized. A better understanding of this process would provide important...

Malfunction and amyloid formation of the Islet Amyloid Polypeptide (IAPP) are factors contributing to Type 2 diabetes. Unravelling the mechanism of IAPP aggregate formation may forward our understanding of this process and its effect on pancreatic β-islet cell. Such mechanistic studies require access to sequence homogeneous and highly pure IAPP. He...

Significance Alzheimer’s disease affects a rapidly growing number of individuals worldwide. Key unresolved questions relate to the onset and propagation of the disease, linked to the self-assembly of amyloid β peptide into fibrillar and smaller aggregates. This study investigates the propagation of aggregates of amyloid β peptide and asks whether h...

The formation of amyloid deposits in human tissues is a defining feature of more than 50 medical disorders, including Alzheimer’s disease. Strong genetic and histological evidence links these conditions to the process of protein aggregation, yet it has remained challenging to identify a definitive connection between aggregation and pathogenicity. U...

Significance Developing effective strategies against human disorders linked with amyloid aggregation, including Alzheimer’s and Parkinson’s diseases, has proven to be difficult. A major reason is that traditional drug-discovery methods are poorly suited to deal with complex reaction networks such as those in involved in the aggregation process. It...

α-Synuclein (α-syn) is an intrinsically disordered protein with a highly asymmetric charge distribution, whose aggregation is linked to Parkinson’s disease. The effect of ionic strength was investigated at mildly acidic pH (5.5) in the presence of catalytic surfaces in the form of α-syn seeds or anionic lipid vesicles using thioflavin T fluorescenc...

Membrane proteins perform a vast range of vital biological functions and are the gatekeepers for exchange of information and matter between the intracellular and extracellular environment. However, membrane protein interactions can be challenging to characterise in a quantitative manner due to the low solubility and large size of the membrane prote...

High purity and sequence homogeneity of intrinsically disordered proteins are prerequisites for reproducible studies of the kinetics and equilibrium of their self-assembly reactions. Starting from the pure state enables quantitative studies of intrinsic and extrinsic factors in the process to understand its molecular determinants. Here we outline d...