Biology subjects

Gautel, M.

Publications and source records attributed to Gautel, M..

4 recordsLinked to original sources

bioRxiv2021

Structure of the thin filament in native skeletal muscles reveals its interaction with nebulin and two distinct conformations of myosin

Nebulin is a major structural protein of skeletal sarcomeres and is essential for proper assembly and contraction of skeletal muscle1. It stabilises and regulates the length of thin filaments,2 but the structural mechanism remains nebulous. Using electron cryotomography and sub-tomogram averaging, we present the first structure of native nebulin bound to thin filaments within the A-band and I-band of intact sarcomeres. This in-situ reconstruction reveals unprecedented detail of interaction at pseudo-atomic resolution between nebulin and actin, providing the basis for understanding the structural and regulatory roles of nebulin. The position of nebulin on the thin filament indicates that there is no contact to tropomyosin or myosin, but an unexpected interaction with a troponin-T linker, possibly through two binding motifs on nebulin. In addition, our structure of myosin bound to the thin filaments reveals different conformations of the neck domain, both within the same sarcomere and when compared to purified structures, highlighting an inherent structural variability in muscle. We provide a complete description of cross-bridge formation on fully native, nebulin-containing thin filaments at near-atomic scale. Our structures establish the molecular basis for the role of nebulin as a thin filament "molecular ruler" and the impact of nemaline myopathies mutations that will aid future development of therapies.

biochemistry↗

bioRxiv2021

Sub-diffraction error mapping for localization microscopy images

Assessing the quality of localization microscopy images is highly challenging due to difficulty in reliably detecting errors in experimental data, with artificial sharpening being a particularly common failure mode of the technique. Here we use Haar wavelet kernel analysis (HAWK), a localization microscopy data analysis method which is known to give results without artificial sharpening, to generate a reference image. This enables the mapping and quantification of this common artefact. By suppressing intensity information, we are able to map sharpening errors in a way which is not influenced by nonlinearity in the localisation imaging process. The HAWK Method for the Assessment of Nanoscopy (HAWKMAN) is a general approach which allows the reliability of localization information to be assessed.

cell biology↗

bioRxiv2020

Molecular Noise-Filtering in the β-adrenergic Signaling Network by Phospholamban Pentamers

Phospholamban (PLN) is an important regulator of calcium handling in cardiomyocytes due to its ability to inhibit the sarco(endo)plasmic reticulum calcium-ATPase (SERCA) {beta}-adrenergic stimulation reverses SERCA inhibition via PLN phosphorylation and facilitates fast calcium reuptake PLN also forms pentamers whose physiological significance has remained elusive Using biochemical experiments and mathematical modeling, we show that pentamers regulate both the dynamics and steady-state levels of monomer phosphorylation Substrate competition by pentamers and a feed-forward loop involving inhibitor-can delay monomer phosphorylation by protein kinase A (PKA) Steady-state phosphorylation of PLN is predicted to be bistable due to cooperative dephosphorylation of pentamers Both effects act as complementary noise-filters which can reduce the effect of random fluctuations in PKA activity Pentamers thereby ensure consistent monomer phosphorylation and SERCA activity in spite of noisy upstream signals Preliminary analyses suggest that the PLN mutation R del could impair noise-filtering, offering a new perspective on how this mutation causes cardiac arrhythmias.

systems biology↗

bioRxiv2020

Molecular plasticity of the native mouse skeletal sarcomere revealed by cryo-ET

Sarcomeres are the force-generating and load-bearing devices of muscles. A precise molecular understanding of how the entire sarcomere is built is required to understand its role in health, disease and ageing. Here, we determine the in situ molecular architecture of vertebrate skeletal sarcomeres through electron cryo-tomography of cryo-focused ion beam-milled native myofibrils. The reconstructions reveal the three-dimensional organisation and interaction of actin and myosin filaments in the A-band, I-band and Z-disc and demonstrate how -actinin cross-links antiparallel actin filaments to form a mesh-like structure in the Z-disc at an unprecedented level of molecular detail. A prominent feature is a so-far undescribed doublet of -actinin cross-links with [~] 6 nm spacing. Sub-volume averaging shows the interaction between myosin, tropomyosin and actin in molecular detail at [~] 10 [A] resolution and reveals two coexisting conformations of actin-bound heads. The flexible orientation of the lever arm and the essential and regulatory light chains allow the two heads of the "double-headed" myosin not only to interact with the same actin filament but also to split between two actin filaments. Our results provide new insights into the conformational plasticity and fundamental organisation of vertebrate skeletal muscle and serve as a strong foundation for future in situ investigations of muscle diseases.

cell biology↗