Biology subjects

Cruz-Leon, S.

Publications and source records attributed to Cruz-Leon, S..

6 recordsLinked to original sources

bioRxiv2024

cryoTIGER: Deep-Learning Based Tilt Interpolation Generator for Enhanced Reconstruction in Cryo Electron Tomography

Cryo-electron tomography enables the visualization of macromolecular complexes within native cellular environments, but is limited by incomplete angular sampling and the maximal electron dose that biological specimen can be exposed to. Here, we developed cryoTIGER (Tilt Interpolation Generator for Enhanced Reconstruction), a computational workflow leveraging a deep learning-based frame interpolation to generate intermediate tilt images. By interpolating between tilt series projections, cryoTIGER improves angular sampling, leading to enhanced 3D reconstructions, more refined particle localization, and improved segmentation of cellular structures. We evaluated our interpolation workflow on diverse datasets and compared its performance against non-interpolated data. Our results demonstrate that deep learning-based interpolation improves image quality and structural recovery. The presented cryoTIGER framework offers a computational alternative to denser sampling during tilt series acquisition, paving the way for enhanced cryo-ET workflows and advancing structural biology research.

molecular biology↗

bioRxiv2024

Passage of the HIV capsid cracks the nuclear pore

Upon infection, human immunodeficiency virus (HIV-1) releases its cone-shaped capsid into the cytoplasm of infected T-cells and macrophages. As its largest known cargo, the capsid enters the nuclear pore complex (NPC), driven by interactions with numerous FG-repeat nucleoporins (FG-Nups). Whether NPCs structurally adapt to capsid passage and whether capsids are modified during passage remains unknown, however. Here, we combined super-resolution and correlative microscopy with cryo electron tomography and molecular simulations to study nuclear entry of HIV-1 capsids in primary human macrophages. We found that cytosolically bound cyclophilin A is stripped off capsids entering the NPC, and the capsid hexagonal lattice remains largely intact inside and beyond the central channel. Strikingly, the NPC scaffold rings frequently crack during capsid passage, consistent with computer simulations indicating the need for NPC widening. The unique cone shape of the HIV-1 capsid facilitates its entry into NPCs and helps to crack their rings.

biophysics↗

bioRxiv2024

Nuclear pores as conduits for fluid flow during osmotic stress

Changing environmental conditions necessitate an immediate cellular adaptation to ensure survival. Dictyostelium discoideum, a bacteriovore slime mold present in the soil of most terrestrial ecosystems, is known for its ability to tolerate drastic changes in osmolarity. How the cells cope with the resulting mechanical stress remains understudied. Here we show that D. discoideum has extraordinarily elaborate and resilient nuclear pores that serve as conduits for massive fluid exchange between cytosol and nucleus. We capitalize on the unique properties of D. discoideum cells to quantify flow across the nuclear envelope that is necessitated by changing nuclear size in response to osmotic stress. Based on mathematical concepts adapted from hydrodynamics, we conceptualize this phenomenon as porous flow across nuclear pores. This type of fluid flow is distinct from the canonically characterized modes of nucleocytoplasmic transport, i.e. passive diffusion and active nuclear transport, because of its dependence on pressure. Our insights are relevant in any biological condition that necessitates rapid nuclear size changes, which includes metastasizing cancer cells squeezing through constrictions, migrating cells and differentiating tissues.

cell biology↗

bioRxiv2023

MolecularWebXR: Multiuser discussions about chemistry and biology in immersive and inclusive VR

MolecularWebXR is a new website for education, science communication and scientific peer discussion in chemistry and biology, based on modern web-based Virtual Reality (VR) and Augmented Reality (AR). With no installs as it is all web-served, MolecularWebXR enables multiple users to simultaneously explore, communicate and discuss concepts about chemistry and biology in immersive 3D environments, by manipulating and passing around objects with their bare hands and pointing at different elements with natural hand gestures. User may either be present in the same real space or distributed around the world, in the latter case talking naturally with each other thanks to built-in audio features. Although MolecularWebXR is most immersive when running in the web browsers of high-end AR/VR headsets, its WebXR core also allows participation by users with consumer devices such as smartphones, possibly inserted into cardboard goggles for deeper immersivity, or even in computers and tablets. MolecularWebXR comes with preset VR rooms that cover topics from general, inorganic and organic chemistry, biophysics and structural biology, and general biology; besides, new content can be added at will through moleculARwebs PDB2AR tool or by contacting the lead authors. We verified MolecularWebXRs ease of use and versatility by people aged 12-80 years old in entirely virtual sessions or in mixed real-virtual sessions at various science outreach events, in courses at the bachelor, masters and early doctoral levels, in scientific collaborations, and in conference lectures. MolecularWebXR is available for free use without registration at https://molecularwebxr.org, and a blog post version of this preprint with embedded videos is available at https://go.epfl.ch/molecularwebxr-blog-post.

scientific communication and education↗

bioRxiv2023

High-confidence 3D template matching for cryo-electron tomography

Cryo-electron tomography (CryoET) resolves individual macromolecules inside living cells. However, the complex composition and high density of cells challenge the faithful identification of features in tomograms. Here, we capitalize on recent advances in electron tomography and demonstrate that 3D template matching (TM) localizes a wide range of structures inside crowded eukaryotic cells with confidence 10 to 100-fold above the noise level. We establish a TM pipeline with systematically tuned parameters for automated, objective and comprehensive feature identification. High-fidelity and high-confidence localizations of nuclear pore complexes, vaults, ribosomes, proteasomes, lipid membranes and microtubules, and individual subunits, demonstrate that TM is generic. We resolve [~]100-kDa proteins, connect the functional states of complexes to their cellular localization, and capture vaults carrying ribosomal cargo in situ. By capturing individual molecular events inside living cells with defined statistical confidence, high-confidence TM greatly speeds up the CryoET workflow and sets the stage for visual proteomics.

molecular biology↗

bioRxiv2023

RNA multiscale simulations as an interplay of electrostatic, mechanical properties, and structures inside viruses

Multiscale simulations have broadened our understanding of RNA structure and function. Various methodologies have enabled the quantification of electrostatic and mechanical interactions of RNA at the nanometer scale. Atom-by-atom simulations, coarse-grained strategies, and continuum models of RNA and its environment provide physical insight and allow to interpret diverse experiments in a systematic way. In this chapter, we present and discuss recent advances in a set of methods to study nucleic acids at different scales. In particular, we introduce details of their parameterization, recent applications, and current limitations. We discuss the interaction of the proteinacous virus capsid, RNA with substrates, compare the properties of RNA and DNA and their interaction with the environment, and analyze the application of these methods to reconstruct the structure of the virus genome structure. Finally, the last lines are dedicated to future developments and challenges ahead.

biophysics↗