Recent advances in quantifying protein conformational ensembles with dipolar EPR spectroscopy
Dastvan R and Stoll S
Recent advances in quantifying protein conformational ensembles with dipolar EPR spectroscopy
Dastvan R and Stoll S
This perspective highlights recent applications and technological progress in dipolar electron paramagnetic resonance (EPR) spectroscopy, including double electron-electron resonance (DEER) spectroscopy. These methods provide nanoscale distance distributions between site-specific spin labels in biomacromolecules. The resulting data are particularly well suited for quantifying the structure and energetics of conformational ensembles of multi-state and flexible proteins. Recent applications span a wide range of systems and are accompanied by innovations in spin labeling, deuteration, in-cell measurements, integrative multi-technique approaches, and novel computational modeling methods combined with structure prediction tools.
2-chlorofatty acid modification of neutrophil proteins: identification, localization and role in NETosis
Carlson HL, McGuffee RM, Patel RP and Ford DA
2-chlorofatty acid modification of neutrophil proteins: identification, localization and role in NETosis
Carlson HL, McGuffee RM, Patel RP and Ford DA
We previously demonstrated neutrophil MPO derived HOCl targets the vinyl ether bond of plasmalogens resulting in the Liberation of 2-chlorofatty aldehydes (2-ClFALDs) and their oxidation products, 2-chlorofatty acids (2-ClFAs), which elicit neutrophil extracellular trap (NET) formation. In this study, the click chemistry analog of 2-chlorohexadecanoic acid (2-ClHA) was utilized to identify 127 proteins covalently modified by 2-ClHA in human neutrophils. Bioinformatics revealed that multiple proteins modified by 2-ClHA are related to protein modification and binding as well as metabolite interconversion. Three key proteins involved in NET formation and function were modified by 2-ClHA including peptidyl arginine deiminase 4 (PAD4), neutrophil defensin alpha 3 (DEFA3), and neutrophil collagenase (MMP8). PAD4 activity was shown to be increased by 2-ClFA treatment. Further studies investigated 2-ClFA modified protein localization over time during NET formation. Initially PAD4 and 2-ClFA-modified proteins were extranuclear but over time they both localized to distinct nuclear regions. Following DNA release from neutrophils, 2-ClFA-modified proteins were found throughout the neutrophil and DNA strands. In summary, multiple neutrophil proteins are modified by 2-ClHA, including PAD4. 2-ClHA modification and activation of PAD4 is suggested as a key component of 2-ClHA elicited NET formation.
Mechanisms of DNMT3A-3L-mediated de novo DNA methylation on chromatin
Yan Y, Zhou XE, Thomas SL, Liu M, Lai GQ, Worden EJ, Jones PA and Xu TH
Mechanisms of DNMT3A-3L-mediated de novo DNA methylation on chromatin
Yan Y, Zhou XE, Thomas SL, Liu M, Lai GQ, Worden EJ, Jones PA and Xu TH
De novo DNA methylation is mediated by DNA methyltransferases DNMT3A and DNMT3B, in cooperation with the catalytically inactive paralogs DNMT3L and DNMT3B3. DNMT3L is predominantly expressed in embryonic stem cells to establish methylation patterns and is silenced upon differentiation, with DNMT3B3 substituting in somatic cells. Here we present high-resolution cryo-electron microscopy structures of nucleosome-bound, full-length DNMT3A2-3L and its oligomeric assemblies in the nucleosome-free state. We identified the critical role of DNMT3L as a histone modification sensor, guiding chromatin engagement through a mechanism distinct from DNMT3B3. The structures show a 180° rotated 'switching helix' in DNMT3L that prevents direct interaction with the nucleosome acidic patch. Instead, nucleosome binding is mediated by the DNMT3L ADD domain, while the DNMT3A PWWP domain exhibits reduced engagement in the absence of H3K36 methylation. The oligomeric arrangement of DNMT3A2-3L in nucleosome-free states highlights its dynamic assembly and potential allosteric regulation. We further capture dynamic structural movements of DNMT3A2-3L on nucleosomes. These findings uncover a previously unknown mechanism by which DNMT3A-3L mediates de novo DNA methylation on chromatin through complex assembly, histone tail sensing, dynamic DNA search and regulated nucleosome engagement, providing insights into epigenetic regulation.
The risk of going outside: Amino phospholipids in rheumatoid arthritis
Pozzi N and Ford DA
The risk of going outside: Amino phospholipids in rheumatoid arthritis
Pozzi N and Ford DA
Voltage sensor conformations induced by LQTS-associated mutations in hERG potassium channels
Chan AN, Quach CD, Handlin LJ, Lessie EN, Tajkhorshid E and Dai G
Voltage sensor conformations induced by LQTS-associated mutations in hERG potassium channels
Chan AN, Quach CD, Handlin LJ, Lessie EN, Tajkhorshid E and Dai G
Voltage sensors are essential for electromechanical coupling in hERG K channels, critical to cardiac rhythm. These sensors respond to membrane potential changes by moving within the transmembrane electric field. Mutations in hERG voltage-sensing arginines, associated with Long-QT syndrome, alter channel gating, though underlying mechanisms remain unclear. Using live-cell fluorescence lifetime imaging microscopy, transition metal FRET, an improved dual stop-codon-mediated strategy for noncanonical amino-acid incorporation, and molecular dynamics simulations, we identify intermediate voltage-sensor conformations induced by neutralizing key arginines in the charge transfer center. Phasor plot analysis of lifetime data reveals multiple voltage-dependent FRET states in these mutants, in contrast to the single high-FRET state observed in controls. These intermediate FRET states reflect distinct conformations of the voltage sensor, corresponding to predicted structures of voltage sensors in molecular dynamics simulations. This study provides insights into cardiac channelopathies, highlighting a structural mechanism that impairs voltage sensing in cardiac arrhythmias.
The Risk of Going Outside: Amino Phospholipids in Rheumatoid Arthritis
Pozzi N and Ford DA
The Risk of Going Outside: Amino Phospholipids in Rheumatoid Arthritis
Pozzi N and Ford DA
Sterile inflammation in laminopathies
de Faria RC and Gonzalo S
Sterile inflammation in laminopathies
de Faria RC and Gonzalo S
Sterile inflammation, an immune response triggered in the absence of pathogens, plays a key role in various chronic diseases, including aging-related disorders, cancer, and autoimmune conditions. This process is driven by damage-associated molecular patterns, such as self-DNA in the cytosol, which activate innate immune pathways and contribute to persistent inflammation. Chronic activation of these pathways exacerbates tissue damage and accelerates disease progression. Recent studies have connected sterile inflammation to laminopathies, a group of genetic disorders caused by mutations in the LMNA gene, which encodes nuclear intermediate filament proteins essential for nuclear structure and function. In this review we discuss the molecular mechanisms underlying sterile inflammation in laminopathies, emphasizing self-DNA sensing, inflammatory signaling cascade activation, and their pathological consequences. Additionally, we explore potential therapeutic strategies aimed at modulating inflammation and improving disease outcomes. Understanding these interactions may provide new avenues for targeting inflammation in laminopathies and related conditions.
Plasminogen mutation-associated thrombotic microangiopathy and role of anticoagulation: a single institution case series
Agarwal S, Pozzi N, Sukumar S, Masias C, Java A and Cataland S
Plasminogen mutation-associated thrombotic microangiopathy and role of anticoagulation: a single institution case series
Agarwal S, Pozzi N, Sukumar S, Masias C, Java A and Cataland S
Knowledge gaps exist regarding the role of coagulation pathway mutations such as those in the plasminogen () gene in the pathogenesis of thrombotic microangiopathy (TMA) and treatment outcomes.
Mechanism of Rad51 filament formation by Rad52 and Rad55-Rad57 in homologous recombination
Deveryshetty J, Mistry A, Pangeni S, Ghoneim M, Tokmina-Lukaszewska M, Gore SK, Liu J, Kaushik V, Karunakaran S, Taddei A, Heyer WD, Ha T, Bothner B and Antony E
Mechanism of Rad51 filament formation by Rad52 and Rad55-Rad57 in homologous recombination
Deveryshetty J, Mistry A, Pangeni S, Ghoneim M, Tokmina-Lukaszewska M, Gore SK, Liu J, Kaushik V, Karunakaran S, Taddei A, Heyer WD, Ha T, Bothner B and Antony E
Homologous recombination (HR) repairs double-stranded DNA breaks (DSBs) by generating single-stranded DNA (ssDNA), which is initially coated by Replication Protein A (Rpa). Rad51, a recombinase, catalyzes strand invasion but binds ssDNA with lower affinity than Rpa, necessitating mediator proteins like Rad52 (yeast) or BRCA2 (humans) for Rad51 loading. The mechanisms of this exchange remain unclear. We show that Saccharomyces cerevisiae Rad52 uses its disordered C-terminus to sort polydisperse Rad51 into discrete monomers. Using fluorescent-Rad51 and single-molecule optical tweezers, we visualize Rad52-mediated Rad51 filament formation on Rpa-coated ssDNA, preferentially at ssDNA-dsDNA junctions. Deleting the C-terminus of Rad52 disrupts Rad51 sorting and loading. Addition of the Rad51 paralog Rad55-Rad57 enhances Rad51 binding by ~60%. Despite structural differences, Rad52 and BRCA2 share conserved functional features. We propose a unified "Sort, Stack & Extend" (SSE) mechanism by which mediator proteins and paralogs coordinate Rad51 filament assembly during HR.
Understanding the structure of β-glycoprotein I: new insights and future paths for antiphospholipid syndrome
Kumar S and Pozzi N
Understanding the structure of β-glycoprotein I: new insights and future paths for antiphospholipid syndrome
Kumar S and Pozzi N
Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by recurrent life-threatening blood clots and pregnancy complications in individuals with antiphospholipid antibodies. Among these antibodies, those targeting the plasma glycoprotein β-glycoprotein I (βGPI) hold particular clinical significance. Despite extensive research, controversies persist regarding the structure of βGPI, which has substantial implications for understanding autoantibody reactivity and APS development. This article critically examines recent advancements in the structural biology of βGPI and its relevance to the recognition of antiphospholipid antibodies. Additionally, it introduces a new structure-based theory to explain how autoantibodies interact with βGPI and the functional consequence of this interaction. Finally, it identifies potential areas for future research that could enhance approaches to diagnosing and treating APS.