Biology subjects

Yengo, C. M.

Publications and source records attributed to Yengo, C. M..

11 recordsLinked to original sources

bioRxiv2026

Disease-associated amino acid substitutions outside canonical motor motifs impair Myo1e localization and activity

Steroid-resistant nephrotic syndrome (SRNS) is a severe kidney disorder characterized by proteinuria and disruption of glomerular filtration, often driven by genetic defects in genes encoding proteins required for podocyte functions. Among these, MYO1E, encoding the actin- and membrane-associated motor protein Myosin 1e (Myo1e), has been implicated in familial and sporadic forms of SRNS. Here, we investigated two MYO1E missense variants, A92E and G562R, identified in trans in a patient with childhood-onset SRNS and located outside canonical P-loop and switch subdomains of the Myo1e motor domain. Both residues are highly conserved, located within predicted -helices in the motor domain, and replaced by larger charged residues, which may reduce protein stability or folding. In podocyte-derived cells, both mutants failed to localize at intercellular junctions and displayed reduced colocalization with actin. The G562R variant additionally formed cytoplasmic aggregates that were partially expression-level-dependent and exhibited decreased fluorescence recovery after photobleaching, indicating impaired protein dynamics. In vitro motility and ATPase assays indicated that the G562R mutant exhibited a marked loss of ATPase activity while the A92E mutant displayed ATPase activity similar to the WT but was characterized by reduced motility and thermal stability. Together, these results demonstrate that A92E and G562R mutations compromise Myo1e localization and function, supporting their pathogenic role in SRNS.

cell biology↗

bioRxiv2026

The Dilated Cardiomyopathy E525K Mutation Stabilizes the Cardiac Myosin Interacting-Heads Motif While Activating the Isolated Motor Domain

Mutations in {beta}-cardiac myosin are a common cause of inherited cardiomyopathies. The dilated cardiomyopathy E525K mutation alters both thick filament regulation and motor activity, yet the structural basis for these effects has remained unclear. Here, we combined cryo-EM and MD simulations to determine how E525K affects the conformational landscape of cardiac myosin in both its autoinhibited interacting-heads motif (IHM) and isolated myosin head states. E525K-mutated myosin exclusively adopted a single S2 conformation in IHM, in contrast to the conformational heterogeneity observed in wild-type myosin. Structural and electrostatic analyses revealed that the mutation increased positive charge density at the blocked-head (BH) - S2 (subfragment-2) interface, strengthening interactions with negatively charged residues within S2. 3D variability analysis and MD simulations of the E525K IHM demonstrated reduced S2 mobility, consistent with strengthened BH - S2 interactions, and decreased conformational flexibility, providing a structural mechanism for stabilization of the IHM state. To investigate the isolated myosin head, we determined cryo-EM structures of wild-type and E525K subfragment-1 (S1). The mutation induced local conformational rearrangements in the activation-loop and Loop 3 region, the SH3-like domain, and the essential light chain of S1, revealing structural changes that support the enhanced motor activity previously reported for isolated E525K myosin motors. These findings show that E525K stabilizes the autoinhibited IHM through electrostatic stabilization of the BH - S2 interface while inducing structural changes consistent with activation of the isolated motor domain, providing structural insights into how a single DCM mutation differentially regulates cardiac myosin S1 and IHM structure and function.

biophysics↗

bioRxiv2026

Hearts may grow concentrically to balance ATP supply and demand and eccentrically to stabilize titin-based stress

Hearts change their wall thickness (concentric growth) and chamber size (eccentric growth) as they adapt to circulatory demands and the intrinsic function of their contractile cells. Factors associated with wall thickening include variants of sarcomeric proteins that enhance contractility, mitochondrial dysfunction, and hypertension. Chambers can dilate due to many factors including sarcomeric variants that depress contractility and aortic and / or mitral valve insufficiency. Despite intensive study, the mechanisms that regulate cardiac growth remain unclear. It is also uncertain whether inherited variants induce growth via the same mechanisms as more common clinical pathologies, such as hypertension. Here we show that computer simulations of a beating left ventricle reproduce both variant and non-variant-related growth patterns when myocytes grow concentrically to regulate intracellular ATP concentration and eccentrically to maintain titin-based intracellular stress. The simulations support the hypothesis that cardiac growth reflects homeostatic feedback through three interacting systems whereby myocytes add or remove mitochondria and sarcomeres (1) in parallel to match ATP generation to myocardial energy demand, and (2) in series to regulate passive tension, while (3) the autonomic nervous system regulates cardiac power, and thus myocardial ATPase, via baroreflex control. The new framework provides a mechanistic basis for the patterns of eccentric and concentric growth induced by a wide range of clinically-relevant conditions and could facilitate in silico testing of potential therapies for cardiac disease. Significance statementHearts grow in response to both physiological and pathological stimuli. The patterns of concentric (wall thickening / thinning) and eccentric (chamber dilation / constriction) induced by different challenges are well recognized but the underlying mechanisms remain unclear. This work presents simulations of a beating left ventricle where (1) concentric growth is regulated by myocytes attempting to stabilize the intracellular ATP concentration and (2) eccentric growth is regulated by titin-mediated stress. The calculations reproduce the growth associated with inherited variants of sarcomeric proteins, mitochondrial dysfunction, hypertension, and both mitral and aortic valve insufficiency. The new ability to predict cardiac growth and its potential modification by treatments, including myotropes, brings the field closer to in silico optimization of therapy for cardiovascular disease.

biophysics↗

bioRxiv2025

Cryo-EM Reveals How Cardiomyopathy Therapeutic Drugs Modulate the Myosin Motors of the Heart

Genetic mutations in myosin, the motor protein that powers the heartbeat, are linked to inherited hypertrophic and dilated cardiomyopathies. Mavacamten and omecamtiv mecarbil are therapeutic, myosin-targeted drugs designed to treat these myopathies, but their mechanism of action has remained unclear. Using single-particle cryo-EM, we determined near-atomic resolution structures of wild-type, mavacamten-bound, and omecamtiv mecarbil-bound myosin molecules. Across all conditions, two conformations of myosin were observed. We show how mavacamten stabilizes one conformation by reinforcing key electrostatic interfaces in the molecule, whereas omecamtiv mecarbil weakens these interfaces, favoring the second structure. This remodeling elucidates previously unclear allosteric mechanisms through which these drugs either inhibit or enhance myosin activity, countering the deleterious impacts of disease. These findings reveal how drugs modulate myosin structure to control cardiac contractility.

biophysics↗

bioRxiv2023

Tail Length and E525K Dilated Cardiomyopathy Mutant Alter Human β-Cardiac Myosin Super-Relaxed State

Dilated cardiomyopathy (DCM) is characterized by impaired cardiac function due to myocardial hypo-contractility and is associated with point mutations in {beta}-cardiac myosin, the molecular motor that powers cardiac contraction. Myocardial function can be modulated through sequestration of myosin motors into an auto-inhibited "super relaxed" state (SRX), which is further stabilized by a structural state known as the "Interacting Heads Motif" (IHM). Therefore, hypo-contractility of DCM myocardium may result from: 1) reduced function of individual myosin, and/or; 2) decreased myosin availability due to increased IHM/SRX stabilization. To define the molecular impact of an established DCM myosin mutation, E525K, we characterized the biochemical and mechanical activity of wild-type (WT) and E525K human {beta}-cardiac myosin constructs that differed in the length of their coiled-coil tail, which dictates their ability to form the IHM/SRX state. Single-headed (S1) and a short-tailed, double-headed (2HEP) myosin constructs exhibited low ([~]10%) IHM/SRX content, actin-activated ATPase activity of [~]5s-1 and fast velocities in unloaded motility assays ([~]2000nm/s). Double-headed, longer-tailed (15HEP, 25HEP) constructs exhibited higher IHM/SRX content ([~]90%), and reduced actomyosin ATPase (<1s-1) and velocity ([~]800nm/s). A simple analytical model suggests that reduced velocities may be attributed to IHM/SRX-dependent sequestration of myosin heads. Interestingly, the E525K 15HEP and 25HEP mutants showed no apparent impact on velocity or actomyosin ATPase at low ionic strength. However, at higher ionic strength, the E525K mutation stabilized the IHM/SRX state. Therefore, the E525K-associated DCM human cardiac hypo-contractility may be attributable to reduced myosin head availability caused by enhanced IHM/SRX stability. SummaryThis research investigates the E525K mutation in human {beta}-cardiac myosin, crucial for heart contraction, and its role in causing Dilated Cardiomyopathy (DCM). It demonstrates that the length of the myosin tail influences its self-inhibition, and the E525K mutation strengthens this effect, potentially reducing heart contractility in DCM.

molecular biology↗

bioRxiv2023

Dilated cardiomyopathy mutation in beta-cardiac myosin enhances actin activation of the power stroke and phosphate release

Inherited mutations in human beta-cardiac myosin (M2{beta}) can lead to severe forms of heart failure. The E525K mutation in M2{beta} is associated with dilated cardiomyopathy (DCM) and was found to stabilize the interacting heads motif (IHM) and autoinhibited super-relaxed (SRX) state in dimeric heavy meromyosin. However, in monomeric M2{beta} subfragment 1 (S1) we found that E525K enhances (3-fold) the maximum steady-state actin-activated ATPase activity (kcat) and decreases (6-fold) the actin concentration at which ATPase is one-half maximal (KATPase). We also found a 3 to 4-fold increase in the actin-activated power stroke and phosphate release rate constants at 30 M actin, which overall enhanced the duty ratio 3-fold. Loaded motility assays revealed that the enhanced intrinsic motor activity translates to increased ensemble force in M2{beta} S1. Glutamate 525, located near the actin binding region in the so-called activation loop, is highly conserved and predicted to form a salt-bridge with another conserved residue (lysine 484) in the relay helix. Enhanced sampling molecular dynamics simulations predict that the charge reversal mutation disrupts the E525-K484 salt-bridge, inducing conformations with a more flexible relay helix and a wide phosphate release tunnel. Our results highlight a highly conserved allosteric pathway associated with actin activation of the power stroke and phosphate release and suggest an important feature of the autoinhibited IHM is to prevent this region of myosin from interacting with actin. The ability of the E525K mutation to stabilize the IHM likely overrides the enhanced intrinsic motor properties, which may be key to triggering DCM pathogenesis. Significance StatementHeart disease can be caused by inherited mutations in beta-cardiac myosin, the molecular motor that powers systolic contraction in the ventricles of the heart. However, it remains unclear how these mutations lead to contractile dysfunction and pathogenic remodeling of the heart. We investigated a unique dilated cardiomyopathy mutation (E525K) that dramatically stabilizes the autoinhibited state while enhancing intrinsic motor function. Thus, we examined how this mutation impacts transient kinetic steps of the ATPase cycle, motile properties, and structural changes associated with the power stroke and phosphate release. Our results provide a kinetic and structural basis for how beta-cardiac myosin mutations may disrupt molecular-level contractile function in complex ways, which may inform the development of targeted therapeutics.

biophysics↗

bioRxiv2022

Conformational changes linked to ADP release from human cardiac myosin bound to actin-tropomyosin

Following binding to the thin filament, {beta}-cardiac myosin couples ATP-hydrolysis to conformational rearrangements in the myosin motor that drive myofilament sliding and cardiac ventricular contraction. However, key features of the cardiac-specific actin-myosin interaction remain uncertain, including the structural effect of ADP release from myosin, which is ratelimiting during force generation. In fact, ADP release slows under experimental load or in the intact heart due to the afterload, thereby adjusting cardiac muscle power output to meet physiological demands. To further elucidate the structural basis of this fundamental process, we used a combination of cryo-EM reconstruction methodologies to determine structures of the human cardiac actin-myosin-tropomyosin filament complex at better than 3.4 [A]-resolution in the presence and in the absence of Mg2+{middle dot}ADP. Focused refinements of the myosin motor head and its essential light chains in these reconstructions reveal that small changes in the active site are coupled to significant rigid body movements of the myosin converter domain and a 16-degree lever arm swing. Our structures provide a mechanistic framework to understand the effect of ADP binding and release on human cardiac {beta}-myosin and offer insights into the force-sensing mechanism displayed by the cardiac myosin motor. Short SummaryCryo-EM was used to elucidate high-resolution structures of actin-tropomyosin filaments decorated with human cardiac myosin in the rigor and ADP-bound states. Differences in the myosin lever arm orientation detected correlate with the overall actomyosin-linked force-sensitivity.

biophysics↗

bioRxiv2022

Dissecting β-Cardiac Myosin and Cardiac Myosin-Binding Protein C Interactions using a Nanosurf Assay

Cardiac myosin-binding protein C (cMyBP-C) regulates cardiac contractility by slowing shortening velocity and sensitizing the thin filament to calcium. cMyBP-C has been shown to interact with the proximal myosin S2 tail and the thin filament. However, the relative contribution of these interactions to the collective modulation of actomyosin ensemble function remains unclear. Hence, we developed a "nanosurf" assay as a model system to interrogate cMyBP-C interactions with actin and/or myosin. Synthetic thick filaments were generated using recombinant human {beta}-cardiac myosin subfragments (HMM or S1) attached to DNA nanotubes, with 14 or 28 nm spacing, corresponding to the 14.3 nm myosin spacing found in native thick filaments. In vitro motility assays with myosin bound to the surrounding surface, exhibit enhanced thin filament interactions with synthetic thick filaments. No significant differences were observed in mean thin filament velocities between 14 and 28 nm spacing, consistent with our previous results for myosin V, VI, and {beta}-cardiac myosin S1. Our nanosurf assay demonstrates the slowing of actomyosin motility by cMyBP-C. Alternating {beta}-cardiac myosin HMM and cMyBP-C N-terminal fragments, C0-C2 or C1-C2, every 14 nm on the nanotube, reduced the mean thin filament velocity 4-6 fold relative to myosin alone. Interestingly, similar inhibition was observed using a {beta}-cardiac myosin S1 construct, which lacks the S2 region proposed to interact with cMyBP-C, suggesting the actin-cMyBP-C interactions may dominate the inhibitory mechanism. No significant inhibition of thin filament velocity was observed with a C0-C1f fragment, lacking the majority of the M-domain, supporting the importance of this domain for inhibitory interaction(s). A phosphomimetic C0-C2 fragment showed a 3-fold higher velocity compared to its phosphonull counterpart, further highlighting phosphorylation-dependent regulation via the M-domain. Together, we have established the nanosurf assay as a tool to precisely manipulate spatially dependent cMyBP-C binding partner interactions, shedding light on the molecular regulation of {beta}-cardiac myosin contractility. STATEMENT OF SIGNIFICANCECardiac myosin-binding protein C (cMyBP-C) is the most frequently mutated protein associated with hypertrophic cardiomyopathy (HCM), a common cause of sudden cardiac death. Despite the importance of cMyBP-C in cardiac contractility, the mechanisms underlying this regulation are unclear due to experimental challenges in studying the complex, transient, weak interactions of cMyBP-C with the contractile proteins of the sarcomere. In this study, we created a nanosurf synthetic DNA thick filament assay to dissect the cMyBP-C interactions with actin and human {beta}-cardiac myosin. We demonstrate actomyosin inhibition by cMyBP-C fragments regardless of recombinant human {beta}-cardiac myosin subfragment (HMM or S1) and highlight the importance of the cMyBP-C M-domain using cMyBP-C fragments and phosphomimetics.

biophysics↗

bioRxiv2022

Dilated cardiomyopathy mutation E525K in human beta-cardiac myosin stabilizes the interacting heads motif and super-relaxed state of myosin

The auto-inhibited, super-relaxed (SRX) state of cardiac myosin is thought to be crucial for regulating contraction, relaxation, and energy conservation in the heart. We used single ATP turnover experiments to demonstrate that a dilated cardiomyopathy (DCM) mutation (E525K) in human beta-cardiac myosin increases the fraction of myosin heads in the SRX state (with slow ATP turnover), especially in physiological ionic strength conditions. We also utilized FRET between a C-terminal GFP tag on the myosin tail and Cy3ATP bound to the active site of the motor domain to estimate the fraction of heads in the closed, interacting-heads motif (IHM); we found a strong correlation between the IHM and SRX state. Negative stain EM and 2D class averaging of the construct demonstrated that the E525K mutation increased the fraction of molecules adopting the IHM. Overall, our results demonstrate that the E525K DCM mutation may reduce muscle force and power by stabilizing the auto-inhibited SRX state. Our studies also provide direct evidence for a correlation between the SRX biochemical state and the IHM structural state in cardiac muscle myosin. Furthermore, the E525 residue may be implicated in crucial electrostatic interactions that modulate this conserved, auto-inhibited conformation of myosin. Significance StatementDilated cardiomyopathy can be caused by single point mutations in cardiac muscle myosin, the motor protein that powers contraction of the myocardium. We found that the E525K DCM mutation in the cardiac myosin heavy chain stabilizes the auto-inhibited, super-relaxed state, suggesting a mechanism by which this mutation reduces muscle force and power. The E525K mutation also highlights critical electrostatic interactions important for forming the conserved, auto-inhibited conformational state of striated muscle myosins.

biophysics↗

bioRxiv2021

Steroid-resistant nephrotic syndrome associated MYO1E mutations have differential effects on myosin 1e localization, dynamics, and activity

Myo1e is a non-muscle motor protein enriched in the podocyte foot processes. Mutations in MYO1E are associated with steroid-resistant nephrotic syndrome (SRNS). Here, we set out to differentiate between the pathogenic and neutral MYO1E variants identified in SRNS patients by exome sequencing. Based on protein sequence conservation and structural predictions, two mutations in the motor domain, T119I and D388H, were selected for this study. EGFP-tagged Myo1e constructs were delivered into the Myo1e-KO podocytes via adenoviral infection to analyze Myo1e protein stability, Myo1e localization, and clathrin-dependent endocytosis, which is known to involve Myo1e activity. Furthermore, truncated Myo1e constructs were expressed using the baculoviral expression system and used to measure Myo1e ATPase and motor activity in vitro. Both mutants were expressed as full-length proteins in the Myo1e-KO podocytes. However, unlike wild-type (WT) Myo1e, the T119I variant was not enriched at the cell junctions or clathrin-coated vesicles (CCVs) in podocytes. In contrast, the D388H variant localization was similar to the WT. Surprisingly, the dissociation of the D388H variant from cell-cell junctions and CCVs was decreased, suggesting that this mutation also affects Myo1e activity. The ATPase activity and the ability to translocate actin filaments were drastically reduced for the D388H mutant, supporting the findings from cell-based experiments. The experimental pipeline developed in this study allowed us to determine that the T119I and D388H mutations appear to be pathogenic and gain additional knowledge in the Myo1e role in podocytes. This workflow can be applied to the future characterization of novel MYO1E variants associated with SRNS.

cell biology↗

bioRxiv2020

Cardiomyopathy Mutations Impact the Power Stroke of Human Cardiac Myosin

Cardiac muscle contraction is driven by the molecular motor myosin that uses the energy from ATP hydrolysis to generate a power stroke when interacting with actin filaments, while it is unclear how this mechanism is impaired by mutations in myosin that can lead to heart failure. We have applied a Forster resonance energy transfer (FRET) strategy to investigate structural changes in the lever arm domain of human {beta}-cardiac myosin subfragment 1 (M2{beta}-S1). We exchanged the human ventricular regulatory light chain labeled at a single cysteine (V105C) with Alexa 488 onto M2{beta}-S1, which served as a donor for Cy3ATP bound to the active site. We monitored the FRET signal during the actin-activated product release steps using transient kinetic stopped-flow measurements. We proposed that the fast phase measured with our FRET probes represents the structural change associated with rotation of the lever arm during the power stroke in M2{beta}-S1. Our results demonstrated human cardiac muscle myosin has a slower power stroke compared with fast skeletal muscle myosin and myosin V. Measurements at different temperatures comparing the rate constants of the power stroke and phosphate release revealed that the power stroke occurs before phosphate release, and the two steps are tightly coupled. We speculate that the slower power stroke rate constant in cardiac myosin may correlate with the slower force development and/or unique thin filament activation properties in cardiac muscle. Additionally, we demonstrated that HCM (R723G) and DCM (F764L) associated mutations both reduced actin-activation of the power stroke in M2{beta}-S1. We also demonstrate that both mutations decrease ensemble force development in the loaded in vitro motility assay. Thus, examining the structural kinetics of the power stroke in M2{beta}-S1 has revealed critical mutation-associated defects in the myosin ATPase pathway, suggesting these measurements will be extremely important for establishing structure-based mechanisms of contractile dysfunction. SignificanceMutations in human beta-cardiac myosin are known to cause various forms of heart disease, while it is unclear how the mutations lead to contractile dysfunction and pathogenic remodeling of the heart. In this study, we investigated two mutations with opposing phenotypes and examined their impact on ATPase cycle kinetics, structural changes associated with the myosin power stroke, and ability to slide actin filaments in the presence of load. We found that both mutations impair the myosin power stroke and other key kinetic steps as well as the ability to produce ensemble force. Thus, our results provide a structural basis for how mutations disrupt molecular level contractile dysfunction.

biophysics↗