Biology subjects

Eichler, J.

Publications and source records attributed to Eichler, J..

5 recordsLinked to original sources

bioRxiv2025

STARD3 coordinates Endoplasmic Reticulum-late endosome/lysosome contacts and organelle positioning through a GSK3-regulated phosphorylation switch

Membrane contact sites (MCS) are dynamic regions where the membranes of two organelles come into close apposition. MCSs play many roles in cellular homeostasis by facilitating inter-organelle lipid and ion exchange as well as organelle positioning. The late endosome/lysosome (LE/Lys) cholesterol transfer protein STARD3 (StAR-related lipid transfer (START) domain containing protein 3) forms reversible contacts between the LE/Lys and the endoplasmic reticulum (ER). This tether protein contains a Phospho-FFAT motif (two phenylalanines (FF) in an acidic tract (AT)) whose interaction with ER-resident VAP proteins is phosphorylation-dependent. In this study, we identify Glycogen Synthase Kinase 3 (GSK3 and GSK3{beta}) as the kinases responsible for phosphorylating serine 209 within the Phospho-FFAT motif of STARD3. This phosphorylation event is both necessary and sufficient to activate STARD3s tethering activity, thereby promoting ER-LE/Lys contacts. Furthermore, we show that the ER-LE/Lys tethering activity made by STARD3 regulates endosome positioning, revealing an additional function for STARD3 on endosome biology. Our findings establish a direct and critical role for GSK3 in regulating MCS dynamics via STARD3 phosphorylation. This novel insight into GSK3-mediated phosphorylation expands our understanding of the molecular mechanisms governing inter-organelle communication.

cell biology↗

bioRxiv2021

The crystal structure of the varicella zoster Orf24-Orf27 nuclear egress complex spotlights multiple determinants of herpesvirus subfamily specificity

Varicella zoster virus (VZV) is a human pathogen from the -subfamily of herpesviruses. Here, the crystal structure of the VZV Orf24-Orf27 complex is described, representing the essential viral core nuclear egress complex (NEC) that orchestrates the egress of the preassembled capsids from the nucleus. While previous studies have primarily emphasized the finding that the architecture of core NEC complexes is highly conserved among herpesviruses, the present report focusses on subfamily-specific structural and functional features that help explain the differences in the autologous versus nonautologous interaction patterns observed for NEC formation across herpesviruses. CoIP and confocal imaging data show that Orf24-Orf27 complex formation displays some promiscuity in a herpesvirus subfamily-restricted manner. At the same time, analysis of the NEC formation thermodynamic parameters of three prototypical -, {beta}- and {gamma} herpesviruses, i.e. VZV, human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) reveals highly similar binding affinities for the autologous interaction with some specific differences in the enthalpy and entropy terms. Computational alanine scanning and structural comparisons highlight intermolecular interactions shared among -herpesviruses that are clearly distinct from those seen in {beta}- and {gamma}-herpesviruses. Combined, these data allow to explain the distinct properties of specificity and permissivity so far observed in herpesviral NEC interactions. These findings might prove highly valuable when attempting to target multiple herpesvirus core NECs with selective or broad-acting drug candidates.

biochemistry↗

bioRxiv2021

A pair of non-competing neutralizing human monoclonal antibodies protecting from disease in a SARS-CoV-2 infection model

TRIANNI mice carry an entire set of human immunoglobulin V region gene segments and are a powerful tool to rapidly generate human monoclonal antibodies. After immunizing these mice against the spike protein of SARS-CoV-2, we identified 29 hybridoma antibodies that reacted with the SARS-CoV-2 spike protein. Nine antibodies neutralized SARS-CoV-2 infection at IC50 values in the subnanomolar range. ELISA-binding studies and DNA sequence analyses revealed one cluster of clonally related neutralizing antibodies that target the receptor-binding domain and compete with the cellular receptor hACE2. A second cluster of neutralizing antibodies binds to the N-terminal domain of the spike protein without competing with the binding of hACE2 or cluster 1 antibodies. SARS-CoV-2 mutants selected for resistance to an antibody from one cluster are still neutralized by an antibody from the other cluster. Antibodies from both clusters markedly reduced viral spread in mice transgenic for human ACE2 and protected the animals from SARS-CoV-2 induced weight loss. Thus, we report two clusters of potent non-competing SARS-CoV-2 neutralizing antibodies providing potential candidates for therapy and prophylaxis of COVID-19. The study further supports the use of transgenic animals with human immunoglobulin gene repertoires in pandemic preparedness initiatives.

immunology↗

bioRxiv2020

3D nanoscale analysis of bone healing around degrading Mg implants studied by X-ray scattering tensor tomography

The nanostructural adaptation of bone is crucial for its compatibility with orthopedic implants. The bones nanostructure determines its mechanical properties, however little is known about its temporal and spatial adaptation in degrading implants. This study presents insights into this adaptation by applying electron microscopy, elemental analysis, and small-angle X-ray scattering tensor-tomography (SASTT). We extend the SASTT reconstruction to multiple radii of the reciprocal space vector q, providing a 3D reciprocal-space map per voxel. Each scattering curve is spatially linked to one voxel in the volume, and properties such as the thickness of the mineral particles are quantified. This reconstruction provides information on nanostructural adaptation during healing around a degrading ZX10 magnesium implant over the course of 18 months, using a sham as control. The nanostructural adaptation process is observed to start with an initially fast interfacial organization towards the implant direction, followed by a substantial reorganization of the volume around the implant, and an adaptation in the later degradation stages. The study sheds light on the complex bone-implant interaction in 3D, allowing a more guided approach towards the design of future implant materials, which are expected to be of great interest for further clinical studies on the bone-implant interaction. TOC text and figureDegrading Magnesium implants are mechanically and chemically well adapted orthopedic implant materials and ensure a gradual load transfer during bone healing due to their degradation. The impact of the implant degradation on the bone nanostructure is however not fully understood. This study unveils the processes 3D and shows different stages of bone healing. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=181 SRC="FIGDIR/small/375253v1_ufig1.gif" ALT="Figure 1"> View larger version (83K): org.highwire.dtl.DTLVardef@1a0ab0borg.highwire.dtl.DTLVardef@13d7486org.highwire.dtl.DTLVardef@1ad4485org.highwire.dtl.DTLVardef@6d9c86_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2020

mRNA secondary structure stability regulates bacterial translation insulation and re-initiation

In bacteria, translation re-initiation is crucial for synthesizing proteins encoded by genes that are organized into operons. The mechanisms regulating translation re-initiation remain, however, poorly understood. We now describe the ribosome termination structure (RTS), a conserved and stable mRNA secondary structure precisely localized downstream of stop codons, which serves as the main factor governing re-initiation efficiency in a synthetic Escherichia coli operon. We further report that in 95% of 128 analyzed bacterial genomes representing all phyla, this structure is selectively depleted when re-initiation is advantageous yet selectively enriched so as to insulate translation when re-initiation is deleterious.

molecular biology↗