Biology subjects

Struckman, H. L.

Publications and source records attributed to Struckman, H. L..

5 recordsLinked to original sources

bioRxiv2026

Stress Granule Coarsening Is a Pathological Inflection Point for Cardiac Electrophysiological Dysfunction

Arrhythmia risk rises early in many forms of cardiac stress, often before contractile failure is evident. Stressed cardiomyocytes accumulate biomolecular condensates, known as stress granules (SGs), whose contribution to this electrical vulnerability has been unclear. We mapped where SGs reside and followed their life cycle under acute and chronic oxidative stress across complementary model systems and assessed electrophysiological consequences with pharmacological tools targeting granule assembly, microtubule integrity, and calcium channel function. Under both stress regimes, SGs localized preferentially to z-lines and intercalated discs, marking these mechanically critical sites as hubs of condensate assembly. Merging of granules, referred to as coarsening, rather than initial formation, emerged as a pathological connection. Early granules were broadly cytoprotective, whereas progressive coarsening was accompanied by disruption of alpha-actinin and L-type calcium channel (Cav1.2) nanodomains and by shortening of action potential (AP) duration. Coarsened granules disorganized Cav1.2 nanodomains through a microtubule-dependent mechanism, and arresting coarsening with nocodazole preserved nanodomain integrity and restored AP morphology. The transition from nascent to coarsened SGs therefore represents a targetable inflection point, and limiting coarsening may prevent proarrhythmic remodeling during cardiac oxidative stress.

bioengineering↗

bioRxiv2026

Common Genetic Variants of The Cardiac Sodium Channel Alter Patient Response to Class 1b Antiarrhythmics

Several common variants have been identified in SCN5A, which encodes the cardiac sodium channel -subunit Nav1.5 and is targeted by class I antiarrhythmics. Lidocaine and its analog mexiletine both have a primary amine that blocks Na+ current. While lidocaine is highly effective in terminating ventricular tachycardia after acute myocardial infarction, mexiletine has been shown to prevent arrhythmia induction in only [~]20% of patients. The factors underlying this inconsistent drug response are unclear. Here, we use cardiomyocytes that are derived from induced pluripotent stem cells to observe that a common polymorphism in the SCN5A gene, S1103Y, exhibits an altered pharmacological response to mexiletine, with enhanced use-dependent and tonic block of peak sodium current. In addition, an unexpected increase in late sodium current causes action potential prolongation. This paradoxical proarrhythmic phenotype shifts the paradigm of conventional antiarrhythmic therapy with mexiletine, suggesting that background variants may alter pharmacological responses leading to unanticipated consequences. Our results suggest that the unique genetic background of patients should inform therapeutic approaches to treat and prevent arrhythmias associated with common cardiac pathologies.

physiology↗

bioRxiv2024

Enantiomeric histidine-rich peptide coacervates enhance antigen delivery to T cells

Peptides and peptidomimetics that self-assemble via LLPS have recently emerged as building blocks for fabricating functional biomaterials due to their unique physicochemical properties and dynamic nature. One of lifes most distinctive signatures is its selectivity for chiral molecules and, to date, coacervates comprised of D-amino acids have not been reported. Here, we demonstrate that histidine-rich repeats of (GHGXY)4 (X=L/V/P) and their enantiomers undergo LLPS opening new avenues for enhancing coacervate stability. Through a series of biophysical studies, we find that LLPS kinetics, droplet size, fusion, and encapsulation efficiency are dictated by the primary sequence. Further, these coacervates can encapsulate therapeutic cargo which are then internalized via endocytic mechanisms. Finally, we show that the coacervates enhance antigen presentation to CD4+ and CD8+ T cells resulting in robust proliferation and production of functional cytokines. Collectively, our study describes the development and characterization of enantiomeric peptide coacervates as attractive vaccine delivery vehicles with tunable physicochemical properties. HIGHLIGHTSO_LID amino acid-peptides were used for the first time to construct phase separating coacervates C_LIO_LIChirality does not restrict LLPS or modulate other coacervate properties C_LIO_LIAntigen delivery using chiral coacervates enhances and prolongs presentation to T cells C_LI PROGRESS AND POTENTIALPeptides can undergo self-assembly via liquid-liquid phase separation (LLPS) to result in solute-rich coacervates that can serve as biomaterials. Using histidine-rich peptide repeats, this work demonstrates that peptides composed of entirely D-amino acids can form functional coaceravtes. The kinetics of LLPS and bulk properties of the droplets can be controlled through simple amino acid substitutions. The coacervates, while immunologically inert, exert an adjuvanting effect and enhance antigen presentation to T cells leading to proliferation and functional cytokine production. The materials showcased here possess high translational potential for combined delivery of immunomodulators and antigens for vaccine delivery against infectious diseases or cancer. The deliverables from this study will also inspire the development of chiral systems that will contribute to the knowledge of cellular processes associated with phase changes integral to both physiology and pathology.

bioengineering↗

bioRxiv2023

Indirect Correlative Light and Electron Microscopy (iCLEM): A Novel Pipeline for Multiscale Quantification of Structure from Molecules to Organs

Correlative light and electron microscopy (CLEM) methods are powerful methods which combine molecular organization (from light microscopy) with ultrastructure (from electron microscopy). However, CLEM methods pose high cost/difficulty barriers to entry and have very low experimental throughput. Therefore, we have developed an indirect correlative light and electron microscopy (iCLEM) pipeline to sidestep the rate limiting steps of CLEM (i.e., preparing and imaging the same samples on multiple microscopes) and correlate multiscale structural data gleaned from separate samples imaged using different modalities by exploiting biological structures identifiable by both light and electron microscopy as intrinsic fiducials. We demonstrate here an application of iCLEM, where we utilized gap junctions and mechanical junctions between muscle cells in the heart as intrinsic fiducials to correlate ultrastructural measurements from transmission electron microscopy (TEM), and focused ion beam scanning electron microscopy (FIB-SEM) with molecular organization from confocal microscopy and single molecule localization microscopy (SMLM). We further demonstrate how iCLEM can be integrated with computational modeling to discover structure-function relationships. Thus, we present iCLEM as a novel approach that complements existing CLEM methods and provides a generalizable framework that can be applied to any set of imaging modalities, provided suitable intrinsic fiducials can be identified.

systems biology↗

bioRxiv2023

Unraveling Chamber-specific Differences in Intercalated Disc Ultrastructure and Molecular Organization and Their Impact on Cardiac Conduction

During each heartbeat, the propagation of action potentials through the heart coordinates the contraction of billions of individual cardiomyocytes and is thus, a critical life process. Unsurprisingly, intercalated discs, which are cell-cell contact sites specialized to provide electrical and mechanical coupling between adjacent cardiomyocytes, have been the focus of much investigation. Slowed or disrupted propagation leads to potentially life-threatening arrhythmias in a wide range of pathologies, where intercalated disc remodeling is a common finding. Hence, the importance and urgency of understanding intercalated disc structure and its influence on action potential propagation. Surprisingly, however, conventional modeling approaches cannot predict changes in propagation elicited by perturbations that alter intercalated disc ultrastructure or molecular organization, owing to lack of quantitative structural data at subcellular through nano scales. In order to address this critical gap in knowledge, we sought to quantify intercalated disc structure at these finer spatial scales in the healthy adult mouse heart and relate them to function in a chamber-specific manner as a precursor to understanding the impacts of pathological intercalated disc remodeling. Using super-resolution light microscopy, electron microscopy, and computational image analysis, we provide here the first ever systematic, multiscale quantification of intercalated disc ultrastructure and molecular organization. By incorporating these data into a rule-based model of cardiac tissue with realistic intercalated disc structure, and comparing model predictions of electrical propagation with experimental measures of conduction velocity, we reveal that atrial intercalated discs can support faster conduction than their ventricular counterparts, which is normally masked by inter-chamber differences in myocyte geometry. Further, we identify key ultrastructural and molecular organization features underpinning the ability of atrial intercalated discs to support faster conduction. These data provide the first stepping stone to elucidating chamber-specific impacts of pathological intercalated disc remodeling, as occurs in many arrhythmic diseases.

physiology↗