Biology subjects

Gursky, O.

Publications and source records attributed to Gursky, O..

6 recordsLinked to original sources

bioRxiv2026

Cryo-EM reveals patient- versus organ-specific structural diversity and bound ligands in lambda-6 light chain amyloids

Immunoglobulin light chain (LC) amyloidosis is a debilitating multiorgan disease with limited treatment options. Sequence and structural variability make LC amyloids particularly challenging for therapeutic targeting. We report four cryo-EM structures of lambda6-LC amyloid fibrils from four organs of two patients. Fibrils from different patients show different N-terminal conformations expanding known repertoire of lambda6-LC amyloid folds. These folds contain a planar beta-arch with a flexible linker containing the complementarity-determining region 2, flanked by N- and C-terminal segments in variable patient-specific conformations. The surface location of the structurally frustrated charged segment may contribute to the overrepresentation of the lambda6-LC family in amyloidosis. These and other lambda6-LC amyloid structures from different patients show different side chain packing. Conversely, cardiac, renal and splenic amyloids from the same patient exhibit similar structures with small peripheral organ-specific variations. Moreover, they show similar orphan densities, suggesting collagen-like triple helices bound to a tyrosine ladder along the fibril spine. Mass spectrometry detects collagen type-VI in tissue-extracted amyloids. Molecular dynamics simulations suggest amyloid binds collagen-VI triple helices via mixed interactions facilitated by the geometric complementarity between the layered amyloid structure and the triple helix. Similar interactions may drive formation of other amyloid-collagen complexes, influencing biological properties of amyloids.

biophysics↗

bioRxiv2026

Small molecule stabilization of diverse amyloidogenic immunoglobulin light chains revealed by hydrogen-deuterium exchange mass spectrometry

Immunoglobulin light chains, a component of antibodies, can misfold and aggregate to cause systemic AL amyloidosis. Aggregation, including amyloid fibril formation, requires unfolding of the full-length light chain from its native state, and in most cases aberrant proteolysis. Small molecules that bind to the native state of light chains to stabilize them against conformational excursions and proteolysis are under development as drug candidates for AL amyloidosis. Since each patient has a unique light chain sequence, a challenge for candidate stabilizer drugs is to bind multiple light chains and suppress their dynamics. Here, we used hydrogen-deuterium exchange measured by mass spectrometry to characterize the binding of six small molecule stabilizers to eleven different {lambda} light chain proteins. Despite structural and dynamic differences among the light chains, the binding of the most efficacious stabilizer molecule led to increased protection from hydrogen exchange, consistent with reduced local and global unfolding. Protection upon binding was most prominent in residues within complementarity determining region 3 and framework region 4 of the light chain variable domains, which undergo major conformational changes enabling amyloid formation. Stabilizer binding also reduced the rate at which all light chains were cleaved by protease. These data show that these stabilizers suppress the range of conformational dynamics associated with light chain aggregation, supporting their therapeutic potential. HighlightsO_LISmall-molecule kinetic stabilizers suppress conformational dynamics and aberrant proteolysis of diverse amyloidogenic full-length {lambda} light chains. C_LIO_LIHDX-MS indicates conserved protection in regions forming the interface between the two variable domains of the light chain dimer, corresponding to residues that form the core of patient-derived amyloid fibrils. C_LIO_LIPLIMSTEX binding titrations show coupled binding, dimerization and stabilization at sub-micromolar kinetic stabilizer concentrations. C_LIO_LISmall molecule kinetic stabilization across different {lambda} sequences supports kinetic stabilizers as a promising therapeutic strategy for AL amyloidosis. C_LI

biophysics↗

bioRxiv2025

Cryo-EM of cardiac AL-224L amyloid reveals shared features in {lambda}6 light chain fibril folds

In amyloid light chain (AL) amyloidosis, aberrant monoclonal antibody light chains (LCs) deposit in vital organs causing organ damage. Each AL patient features a unique LC. Previous cryogenic electron microscopy (cryo-EM) studies revealed different amyloid structures in different AL patients. How LC mutations influence amyloid structures remains unclear. We report a cryo-EM structure of cardiac AL-224L amyloid (2.92 [A] resolution) from {lambda}6-LC family, which is overrepresented in amyloidosis. Comparison with {lambda}6-LC structures from two other patients reveals similarities in amyloid folds. Mutation-induced structural differences in AL-224L include altered C-terminal conformation with an exposed ligand-binding surface; an enlarged hydrophilic pore with orphan density; and altered steric zipper registry with backbone flipping, which likely represent general adaptive mechanisms in amyloids. The results suggest shared features in {lambda}6-LC amyloid folds and reveal how mutation-induced structural changes influence amyloid-ligand interactions in a patient-specific manner.

biophysics↗

bioRxiv2023

Molecular modeling of apoE in complexes with Alzheimers amyloid-beta fibrils from human brain suggests a structural basis for apolipoprotein co-deposition with amyloids

Apolipoproteins co-deposit with amyloids, yet apolipoprotein-amyloid interactions are enigmatic. To understand how apoE interacts with Alzheimers amyloid-{beta} (A{beta}) peptide in fibrillary deposits, the NMR structure of full-length human apoE was docked to four structures of patient-derived A{beta}1-40 and A{beta}1-42 fibrils determined previously using cryo-electron microscopy or solid-state NMR. Similar docking was done using the NMR structure of human apoC-III. In all complexes, conformational changes in apolipoproteins were required to expose large hydrophobic faces of their amphipathic -helices for sub-stoichiometric binding to hydrophobic surfaces on sides or ends of fibrils. Basic residues flanking the hydrophobic helical faces in apolipoproteins interacted favorably with acidic residue ladders in some amyloid polymorphs. Molecular dynamics simulations of selected apoE-fibril complexes confirmed their stability. Amyloid binding via cryptic sites, which became available upon opening of flexibly linked apolipoprotein -helices, resembled apolipoprotein-lipid binding. This mechanism probably extends to other apolipoprotein-amyloid interactions. Apolipoprotein binding alongside fibrils could interfere with fibril fragmentation and secondary nucleation, while binding at the fibril ends could halt amyloid elongation and dissolution in a polymorph-specific manner. The proposed mechanism is supported by extensive prior experimental evidence and helps reconcile disparate reports on apoEs role in A{beta} aggregation. Furthermore, apoE domain opening and direct interaction of Arg/Cys158 with amyloid potentially contributes to isoform-specific effects in Alzheimers disease. In summary, current modeling supported by prior experimental studies suggests similar mechanisms for apolipoprotein-amyloid and apolipoprotein-lipid interactions; explains why apolipoproteins co-deposit with amyloids; and helps reconcile conflicting reports on the chaperone-like apoE action in A{beta} aggregation.

biophysics↗

bioRxiv2023

Role of Complementarity-Determining Regions 1 and 3 in Pathologic Amyloid Formation by Human Immunoglobulin κ1 Light Chains

Immunoglobulin light chain (LC) amyloidosis is a life-threatening disease whose understanding and treatment is complicated by vast numbers of patient-specific mutations. To address molecular origins of the disease, we explored 14 patient-derived and engineered proteins related to {kappa}1-family germline genes IGKVLD-33*01 and IGKVLD-39*01. Hydrogen-deuterium exchange mass spectrometry analysis of local conformational dynamics in full-length recombinant LCs and their fragments was integrated with studies of thermal stability, proteolytic susceptibility, amyloid formation, and amyloidogenic sequence propensities using spectroscopic, electron microscopic and bioinformatics tools. The results were mapped on the atomic structures of native and fibrillary proteins. Proteins from two {kappa}1 subfamilies showed unexpected differences. Compared to their germline counterparts, amyloid LC related to IGKVLD-33*01 was less stable and formed amyloid faster, whereas amyloid LC related to IGKVLD-39*01 had similar stability and formed amyloid slower. These and other differences suggest different major factors influencing amyloid formation. In 33*01-related amyloid LC, these factors involved mutation-induced destabilization of the native structure and probable stabilization of amyloid. The atypical behaviour of 39*01-related amyloid LC tracked back to increased dynamics/exposure of amyloidogenic segments in {beta}CV and {beta}EV that could initiate aggregation, combined with decreased dynamics/exposure near the Cys23-Cys88 disulfide whose rearrangement is rate-limiting to amyloidogenesis. The results suggest distinct amyloidogenic pathways for closely related LCs and point to the antigen-binding, complementarity-determining regions CDR1 and CDR3, which are linked via the conserved internal disulfide, as key factors in amyloid formation by various LCs.

biochemistry↗

bioRxiv2018

Molecular basis for a novel systemic form of human hereditary apoA-I amyloidosis with vision loss

Hereditary apolipoprotein A-I (apoA-I) amyloidosis (AApoAI) is a life-threatening incurable genetic disorder whose molecular underpinnings and the full spectrum of afflicted organs are unclear. We report a new form of AApoAI with amyloid deposition in multiple organs, including an unprecedented retinal amyloidosis. Genetic and proteomic analyses identified Glu34Lys apoA-I as the fibrillar protein causing the clinical manifestations. A life-saving combined hepatorenal transplantation was performed for one Glu34Lys carrier. To elucidate structural underpinnings for amyloidogenic properties of Glu34Lys, we generated its recombinant globular domain and compared the conformation and dynamics of its lipid-free form with those of two other naturally occurring apoA-I variants, Phe71Tyr (amyloidogenic) and Leu159Arg (non-amyloidogenic). All variants showed reduced stability and altered aromatic residue packing. Molecular dynamics simulations revealed local helical unfolding and suggested that transient opening of Trp72 induced mutation-dependent structural perturbations in a sensitive region, including the major amyloid hotspot residues 14-22. We posit that a shift from the \"closed\" to an \"open\" orientation of Trp72 modulates structural protection of amyloid hotspots, suggesting a previously unknown early step in protein misfolding.

molecular biology↗