Biology subjects

Robert-Paganin, J.

Publications and source records attributed to Robert-Paganin, J..

7 recordsLinked to original sources

bioRxiv2026

Plasmodium falciparum Myosin B is a slow motor optimized for force generation

Malaria is a disease caused by apicomplexan parasites of the genus Plasmodium. These organisms express two atypical class-XIV myosins: Myosin A (MyoA), a core component of the glideosome expressed throughout the entire lifecycle, and Myosin B (MyoB), which is restricted to invasive stages and localizes to the apical region. Here, we determine the crystal structure of Plasmodium falciparum MyoB (PfMyoB) in the Rigor state and identify its essential light chain as the same subunit bound to MyoA. Combining structural analysis, molecular dynamics simulations and in vitro kinetic and motility assays, we show that PfMyoB is a slow motor optimized for force production during invasion. The N-terminal extensions of PfMyoA and PfMyoB exert distinct effects on each motor s mechanochemistry. Altogether, these findings reveal how Plasmodium myosins have evolved specialized functions during the complex parasite lifecycle and provide insight into developing multi-target inhibitors of erythrocytic invasion based on the PfMyoA inhibitor KNX-002.

biophysics↗

bioRxiv2023

Omecamtiv mecarbil and Mavacamten target the same myosin pocket despite antagonistic effects in heart contraction

Inherited cardiomyopathies are amongst the most common cardiac diseases worldwide, leading in the late-stage to heart failure and death. The most promising treatments against these diseases are small-molecules directly modulating the force produced by {beta}-cardiac myosin, the molecular motor driving heart contraction. Two of these molecules that produce antagonistic effects on cardiac contractility have completed clinical phase 3 trials: the activator Omecamtiv mecarbil and the inhibitor Mavacamten. In this work, we reveal by X-ray crystallography that both drugs target the same pocket and stabilize a pre-stroke structural state, with only few local differences. All atoms molecular dynamics simulations reveal how these molecules can have antagonistic impact on the allostery of the motor by comparing {beta}-cardiac myosin in the apo form or bound to Omecamtiv mecarbil or Mavacamten. Altogether, our results provide the framework for rational drug development for the purpose of personalized medicine.

molecular biology↗

bioRxiv2023

Cryo-EM structure of the folded-back state of human β-cardiac myosin

During normal levels of exertion, many cardiac muscle myosin heads are sequestered in an off-state even during systolic contraction to save energy and for precise regulation. They can be converted to an on-state when exertion is increased. Hypercontractility caused by hypertrophic cardiomyopathy (HCM) myosin mutations is often the result of shifting the equilibrium toward more heads in the on-state. The off-state is equated with a folded-back structure known as the interacting head motif (IHM), which is a regulatory feature of all muscle myosins and class-2 non-muscle myosins. We report here the human {beta}-cardiac myosin IHM structure to 3.6 [A] resolution. The structure shows that the interfaces are hot spots of HCM mutations and reveals details of the significant interactions. Importantly, the structures of cardiac and smooth muscle myosin IHMs are dramatically different. This challenges the concept that the IHM structure is conserved in all muscle types and opens new perspectives in the understanding of muscle physiology. The cardiac IHM structure has been the missing puzzle piece to fully understand the development of inherited cardiomyopathies. This work will pave the way for the development of new molecules able to stabilize or destabilize the IHM in a personalized medicine approach. *This manuscript was submitted to Nature Communications in August 2022 and dealt efficiently by the editors. All reviewers received this version of the manuscript before 9208 August 2022. They also received coordinates and maps of our high resolution structure on the 18208 August 2022. Due to slowness of at least one reviewer, this contribution was delayed for acceptance by Nature Communications and we are now depositing in bioRxiv the originally submitted version written in July 2022 for everyone to see. Indeed, two bioRxiv contributions at lower resolution but adding similar concepts on thick filament regulation were deposited this week in bioRxiv, one of the contributions having had access to our coordinates. We hope that our data at high resolution will be helpful for all readers that appreciate that high resolution information is required to build accurate atomic models and discuss implications for sarcomere regulation and the effects of cardiomyopathy mutations on heart muscle function.

biophysics↗

bioRxiv2022

Mechanism of small molecule inhibition of Plasmodium falciparum myosin A informs antimalarial drug design

Malaria is responsible for more than a half million deaths per year. The Plasmodium parasites responsible continue to develop resistance to all known agents, despite treatment with different antimalarial combinations. The atypical Myosin A motor (PfMyoA) is part of a core macromolecular complex called the glideosome, essential for Plasmodium parasite mobility and therefore an attractive drug target. Here, we characterize the interaction of a small molecule (KNX-002) with PfMyoA. KNX-002 inhibits PfMyoA ATPase activity in vitro and blocks asexual blood stage growth of merozoites, one of three motile Plasmodium life-cycle stages. Combining biochemical assays, X-ray crystallography and molecular dynamics, we demonstrate that KNX-002 targets a novel pocket in PfMyoA, sequestering it in a post-rigor state detached from actin. KNX-002 binding affects Mg2+ coordination near ATP, preventing ATP hydrolysis and thus inhibiting motor activity. This first-in-class small-molecule inhibitor of PfMyoA paves the way for developing a new generation of antimalarial treatments.

molecular biology↗

bioRxiv2022

Dexamethasone, a direct modulator of AQP2 in Meniere s disease.

Menieres disease is a chronic illness characterized by intermittent episodes of vertigo associated with fluctuating sensorineural hearing loss, tinnitus and aural pressure. This pathology strongly correlates with a dilatation of the fluid compartment of the endolymph, so-called hydrops. Dexamethasone is one of the therapeutic approaches recommended when conventional antivertigo treatments have failed. Several mechanisms of actions have been hypothesized for the mode of action of dexamethasone such as anti-inflammatory effect or as a regulator of the inner ear water homeostasis. However, none of them have been experimentally confirmed so far. Aquaporins (AQPs) are transmembrane water channels and are hence central in the regulation of trans-cellular water fluxes. In the present study we investigated the hypothesis that dexamethasone could impact water fluxes in the inner ear through direct interaction with AQP2. We addressed this question through molecular dynamics simulations approaches and managed to demonstrate a direct interaction between AQP2 and dexamethasone and its significant impact on the channel water permeability. We also describe the molecular mechanisms involved in dexamethasone binding and in its regulatory action upon AQP2 function. HighlightsO_LIAQP2 water permeability is modulated by dexamethasone at physiological concentrations C_LIO_LIThe interaction impacts water fluxes through a direct interaction with the extra-cellular surface of the aquaporin C_LIO_LIKey interactions implicate conserved residues of the ar/R constriction C_LIO_LINew insights on corticosteroids mode of actions in Menieres disease treatment C_LI

biochemistry↗

bioRxiv2020

Structure of Full Length Plasmodium Myosin A and its light chain PfELC, dual targets against malaria parasite pathogenesis

Parasites from the genus Plasmodium are the causative agents of malaria. The mobility, infectivity and ultimately pathogenesis of this parasite relies on a macromolecular complex, called the glideosome. At the core of the glideosome is an essential and divergent Myosin A motor (PfMyoA), a first order drug target against malaria. Here we present the full-length structure of PfMyoA in two states of its motor cycle. We report novel interactions that are essential for motor priming and the mode of recognition of its two light chains (PfELC and MTIP) by two degenerate IQ motifs. Kinetic and motility assays using PfMyoA variants, along with molecular dynamics, demonstrate how specific priming and atypical sequence adaptations tune the motor’s mechano-chemical properties. Supported by evidence for an essential role of the PfELC in malaria pathogenesis, these structures provide a blueprint for the design of future antimalarials targeting both the glideosome motor and its regulatory elements.HighlightsThe first structures of the full length PfMyoA motor in two states of its motor cycle.A unique priming of the PfMyoA lever arm results from specific lever arm/motor domain interactions, which allows for a larger powerstroke to enhance speed.Sequence adaptations within the motor domain and degenerate IQ motifs in the lever arm dictate PfMyoA motor properties.PfELC is essential for blood cell invasion and is a weak link in the assembly of a fully functional motor, providing a second novel target for antimalarial drug design.Competing Interest StatementThe authors have declared no competing interest.View Full Text

biochemistry↗

bioRxiv2018

Hypertrophic cardiomyopathy disease results from disparate impairments of cardiac myosin function and auto-inhibition

AbstractHypertrophic cardiomyopathies (HCM) result from distinct single-point mutations in sarcomeric proteins that lead to muscle hypercontractility. While different models account for a pathological increase in the power output, clear understanding of the molecular basis of dysfunction in HCM is the mandatory next step to improve current treatments. An optimized quasi-atomic model of the sequestered state of cardiac myosin coupled to X-ray crystallography and in silico analysis of the mechanical compliance of the lever arm allowed us to perform a systematic study for a large set of HCM mutations. We define different classes of mutations depending on their effects on lever arm compliance, sequestered state stability and motor functions. This work reconciles previous models and explains how distinct HCM mutations can have disparate effects on the motor mechano-chemical parameters and yet lead to the same disease. The framework presented here can guide future investigations aiming at finding HCM treatments.

biophysics↗