Biology subjects

Rentsch, J.

Publications and source records attributed to Rentsch, J..

6 recordsLinked to original sources

bioRxiv2024

CONDENSATES OF SYNAPTIC VESICLES AND SYNAPSIN ARE MOLECULAR BEACONS FOR ACTIN SEQUESTERING AND POLYMERIZATION

Neuronal communication relies on precisely maintained synaptic vesicle (SV) clusters, which assemble via liquid-liquid phase separation (LLPS). This process requires synapsins, the major synaptic phosphoproteins, which are known to bind actin. The reorganization of SVs, synapsins and actin is a hallmark of synaptic activity, but their interplay is still unclear. Here, we combined the reconstitution approaches, expansion microscopy, super-resolution imaging and cryo-electron tomography to dissect the roles of synapsin-SV condensates in the organization of the presynaptic actin cytoskeleton. Our data indicate that LLPS of synapsin initiates actin polymerization, allowing for SV:synapsin:actin assemblies to facilitate the mesoscale organization of SV clusters along axons mimicking the native presynaptic organization in both lamprey and mammalian synapses. Understanding the relationship between the actin network and synapsin-SVs condensates is an essential building block on a roadmap to unravel how coordinated neurotransmission along the axon enables circuit function and behavior.

cell biology↗

bioRxiv2023

Comparative transcriptomics of Venus flytrap (Dionaea muscipula) across stages of prey capture and digestion

The Venus flytrap, Dionaea muscipula, is perhaps the worlds best-known botanical carnivore. The act of prey capture and digestion along with its rapidly closing, charismatic traps make this species a compelling model for studying the evolution and fundamental biology of carnivorous plants. There is a growing body of research on the genome, transcriptome, and digestome of Dionaea muscipula, but surprisingly limited information on changes in trap transcript abundance over time since feeding. Here we present the results of a comparative transcriptomics project exploring the transcriptomic changes across seven timepoints in a 72-hour time series of prey digestion and three timepoints directly comparing triggered traps with and without prey items. We document a dynamic response to prey capture including changes in abundance of transcripts with Gene Ontology (GO) annotations related to digestion and nutrient uptake. Comparisons of traps with and without prey documented 174 significantly differentially expressed genes at 1 hour after triggering and 151 genes with significantly different abundances at 24 hours. Approximately 50% of annotated protein-coding genes in Venus flytrap genome exhibit change (10041 of 21135) in transcript abundance following prey capture. Whereas peak abundance for most of these genes was observed within 3 hours, an expression cluster of 3009 genes exhibited continuously increasing abundance over the 72-hour sampling period, and transcript for these genes with GO annotation terms including both catabolism and nutrient transport may continue to accumulate beyond 72 hours.

plant biology↗

bioRxiv2023

Sub-membrane actin rings compartmentalize the plasma membrane

The compartmentalization of the plasma membrane is a fundamental feature of cells. The diffusivity of membrane proteins in the plane of the membrane is significantly lower in cells than observed in artificial membranes. This seems due to the sub-membranous actin cortex, but tractable assays to prove a direct dependence of membrane protein motion on actin filaments have been elusive. We recently showed that a periodic array of sub-membrane actin filaments that surround neuronal axons in ring-like structures in the axonal initial segment (AIS) confines membrane protein motion between them, but the local enrichment of ion channels may offer an alternative explanation for compartmentalization. Here we show using computational modeling that in contrast to actin rings, the dense array of ion channels in the AIS cannot mediate membrane protein confinement. We go on to show that indeed the actin rings are closely apposed to the plasma membrane, and that they confine membrane protein motion between them in a [~] 200 nm periodic pattern in progenitor-derived neuronal cells. We find that this compartmentalization is also detectable for inner-leaflet membrane proteins and multi-spanning receptors. Strikingly, several cell types with actin rings in their protrusions, like progenitor-derived astrocytes and oligodendrocytes, also exhibit lateral confinement of membrane proteins in a periodic pattern consistent with actin ring spacing. Actin ring-mediated membrane compartmentalization is thus not unique to neurons. Finally, we show that acute actin disruption in live progenitor-derived neuronal cells leads to a loss of membrane compartmentalization in areas that were compartmentalized before treatment. Taken together, we here develop a much-needed tractable experimental system for the investigation of membrane compartmentalization and show that actin rings compartmentalize the plasma membrane of cells.

biophysics↗

bioRxiv2021

Precise measurement of nanoscopic septin ring structures in deep learning-assisted quantitative superresolution microscopy

The combination of image analysis and fluorescence superresolution microscopy methods allows for unprecedented insight into the organization of macromolecular assemblies in cells. Advances in deep learning-based object recognition enables the automated processing of large amounts of data, resulting in high accuracy through averaging. However, while the analysis of highly symmetric structures of constant size allows for a resolution approaching the dimensions of structural biology, deep learning methods are prone to different forms of bias. A biased recognition of structures may prohibit the development of readouts for processes that involve significant changes in size or shape of amorphous macromolecular complexes. What is required to overcome this problem is a detailed investigation of potential sources of bias and the rigorous testing of trained models using real or simulated data covering a wide dynamic range of possible results. Here we combine single molecule localization-based superresolution microscopy of septin ring structures with the training of several different deep learning models for a quantitative investigation of bias resulting from different training approaches and finally quantitative changes in septin ring structures. We find that trade-off exists between measurement accuracy and the dynamic range of recognized phenotypes. Using our trained models, we furthermore find that septin ring size can be explained by the number of subunits they are assembled from alone. Our work provides a new experimental system for the investigation of septin polymerization.

cell biology↗

bioRxiv2020

The postsynaptic MAGUK scaffold protein MPP2 organises a distinct interactome that incorporates GABAA receptors at the periphery of excitatory synapses

Recent advances in imaging technology have highlighted that scaffold proteins and receptors are arranged in sub-synaptic nanodomains. The synaptic MAGUK scaffold protein MPP2 is a component of AMPA receptor-associated protein complexes and also binds to the synaptic cell adhesion molecule SynCAM1. Using super-resolution imaging, we now show that MPP2 and SynCAM1 are situated at the periphery of the postsynaptic density. In order to explore MPP2-associated protein complexes, we used a quantitative comparative mass spectrometry approach and identified multiple GABAA receptor subunits among the novel synaptic MPP2 interactors. We further show that GABAA receptors are found together with MPP2 in a subset of dendritic spines and thus highlight MPP2 as a scaffold molecule capable of acting as an adaptor molecule that links peripheral synaptic elements critical for inhibitory regulation to central structures at the PSD of glutamatergic synapses.

neuroscience↗

bioRxiv2020

Directed manipulation of membrane proteins by fluorescent magnetic nanoparticles

The plasma membrane is the interface through which cells interact with their environment. Membrane proteins are embedded in the lipid bilayer of the plasma membrane and their function in this context is often linked to their specific location and dynamics within the membrane. However, few methods are available for nanoscale manipulation of membrane protein location at the single molecule level. Here, we report the use of fluorescent magnetic nanoparticles (FMNPs) to track membrane molecules and to manipulate their movement. FMNPs allow single-particle tracking (SPT) at 10 nm spatial and 5 ms temporal resolution, and using a magnetic needle, we pull membrane components laterally through the membrane with femtonewton-range forces. In this way, we successfully dragged lipid-anchored and transmembrane proteins over the surface of living cells. Doing so, we detected submembrane barriers and in combination with super-resolution microscopy could localize these barriers to the actin cytoskeleton. We present here a versatile approach to probe membrane processes in live cells via the magnetic control of membrane protein motion.

biophysics↗