Biology subjects

Rossmann, K.

Publications and source records attributed to Rossmann, K..

7 recordsLinked to original sources

bioRxiv2025

A silicon rhodamine-fused glibenclamide to label and detect malaria-infected red blood cells

The malaria parasite Plasmodium falciparum affects the lives of millions of people worldwide every year. The detection of replicating parasites within human red blood cells is of paramount importance, requiring appropriate diagnostic tools. Herein, we design and apply a silicon rhodamine-fused glibenclamide (SiR-glib). We first test this far-red fluorescent, fluorogenic and endoplasmic reticulum-targeting sulfonylurea in mammalian cells and pancreatic tissues, before characterizing its labeling performance in red blood cells infected with the asexual developmental stages of Plasmodium falciparum. We further combine SiR-glib with a portable smartphone-based microscope to easily and rapidly identify parasitized red blood cells, providing proof of principle for diagnostic use in rural endemic areas without major healthcare facilities.

biochemistry↗

bioRxiv2024

A one-step protocol to generate impermeable fluorescent HaloTag substrates for in situ live cell application and super-resolution imaging

Communication between cells is largely orchestrated by proteins on the cell surface, which allow information transfer across the cell membrane. Super-resolution and single-molecule visualization of these proteins can be achieved by genetically grafting HTP (HaloTag Protein) into the protein of interest followed by brief incubation of cells with a dye-HTL (dye-linked HaloTag Ligand). This approach allows for use of cutting-edge fluorophores optimized for specific optical techniques or a cell-impermeable dye-HTL to selectively label surface proteins without labeling intracellular copies. However, these two goals often conflict, as many high-performing dyes exhibit membrane permeability. Traditional methods to eliminate cell permeability face synthetic bottlenecks and risk altering photophysical properties. Here we report that dye-HTL reagents can be made cell-impermeable by inserting a charged sulfonate directly into the HTL, leaving the dye moiety unperturbed. This simple, one-step method requires no purification and is compatible with both the original HTL and second-generation HTL.2, the latter offering accelerated labeling. We validate such compounds, termed dye-SHTL ( dye shuttle) conjugates, in live cells via widefield microscopy, demonstrating exclusive membrane staining of extracellular HTP fusion proteins. In transduced primary hippocampal neurons, we label mGluR2, a neuromodulatory G protein-coupled receptor (GPCR), with dyes optimized for stimulated emission by depletion (STED) super-resolution microscopy, allowing unprecedented accuracy in distinguishing surface and receptors from those in internal compartments of the presynaptic terminal, important in neural communication. This approach offers broad utility for surface-specific protein labelling.

pharmacology and toxicology↗

bioRxiv2024

Melanocortin system activates carotid body arterial chemoreceptors in hypertension

BackgroundThe bodys internal milieu is controlled by a system of interoceptors coupled to motor outflows that drive compensatory adaptive responses. These include the arterial chemoreceptors, best known for sensing arterial oxygen. In cardiometabolic diseases, such as essential hypertension, the carotid bodies (CB) exhibit heightened reflex sensitivity and tonic activity without an apparent stimulus. The mechanisms behind CB sensitization in these conditions are not well understood. MethodsGuided by functional genomics, a range of functional assays is used to interrogate downstream intracellular and interorgan signalling pathways involved in arterial chemosensory function. ResultsHere, we report the presence of the Melanocortin 4 receptor (MC4R) in the mammalian CB and show its elevated expression in experimental hypertension. We demonstrate that melanocortin agonists activate arterial chemosensory cells, modulating CB chemosensory afferent drive to influence both resting and chemoreflex-evoked sympathetic and ventilatory activity. Transcriptional analysis of hypertensive CB implicates the activation of the Mash1 (Ascl1) regulatory network in driving elevated Mc4r expression. ConclusionsCollectively, our data indicate a primarily pathophysiological role of melanocortin signalling in arterial chemosensation, contributing to excess sympathetic activity in cardiometabolic disease.

neuroscience↗

bioRxiv2023

Deuteration provides a general strategy to enhance azobenzene-based photopharmacology

Herein, we present deuterated azobenzene photoswitches as a general means of enhancing photopharmacological molecules. Deuteration can improve azobenzene performance in terms of light sensitivity, photoswitch efficiency, and photoswitch kinetics with minimal alteration to the underlying structure of the photopharmacological ligand. We report synthesized deuterated azobenzene-based ligands for the optimized optical control of ion channel and G protein-coupled receptor function in live cells, setting the stage for the straightforward, widespread adoption of this approach.

biochemistry↗

bioRxiv2022

A versatile Halo- and SNAP-tagged BMP/TGFβ receptor library for quantification of cell surface ligand binding

The TGF{beta} superfamily of secreted growth factors comprises more than 30 members including TGF{beta}s, BMPs and Activins. While all TGF{beta} superfamily members signal through heteromeric receptor complexes to regulate a plethora of developmental and homeostatic processes, each ligand possesses a unique affinity towards a subset of BMP and TGF{beta} type I and type II receptors. Whereas the Activin and TGF{beta} class display a higher affinity towards type II receptors, BMPs and GDFs preferentially bind to type I receptors. Sofar, the lack of specific antibodies and chemical biology tools hampered simultaneous testing of ligand binding towards all BMP and TGF{beta} receptors. Here we present a N-terminally Halo- and SNAP-tagged TGF{beta}/BMP receptor library to visualize the receptor complexes in dual color. In combination with novel fluorescently labeled TGF{beta} superfamily ligands, we established a Ligand Surface Binding Assay (LSBA) for optical quantification of receptor-dependent growth factor binding for Activin A, TGF{beta}1 and BMP9 in a cellular context. We confirm ligand-receptor interface specificity by identifying BMPR2- or ALK2-mutants that switch from a low-affinity Activin A- or BMP9-receptor to a high-affinity receptor, respectively.

cell biology↗

bioRxiv2021

Sulfonated rhodamines as impermeable labelling substrates for cell surface protein visualization

Sulfonated rhodamines that endow xanthene dyes with cellular impermeability are presented. We fuse charged sulfonates to red and far-red dyes to obtain Sulfo549 and Sulfo646, respectively, and further link these to SNAP- and Halo-tag substrates for protein self-labelling. Cellular impermeability is validated in live cell imaging experiments in transfected HEK cells and neurons derived from induced pluripotent stem cells (iPSCs). Lastly, we show that Sulfo646 is amenable to STED nanoscopy by recording membranes of SNAP/Halo-surface-labelled human iPSC-derived neuronal axons. We therefore provide an avenue for rendering dyes impermeable for exclusive extracellular visualization via self-labelling protein tags.

biochemistry↗

bioRxiv2020

Deuterated rhodamines for protein labelling in nanoscopy

Rhodamine molecules are setting benchmarks in fluorescence microscopy. Herein, we report the deuterium (d12) congeners of tetramethyl(silicon)rhodamine, obtained by isotopic labelling of the four methyl groups, which improves photophysical (i.e. brightness, lifetimes) and chemical (i.e. bleaching) properties. We explore this finding for SNAP- and Halo-tag labelling, and highlight enhanced properties in several applications, such as Forster resonance energy transfer, fluorescence activated cell sorting, fluorescence lifetime microscopy and stimulated emission depletion nanoscopy. We envision deuteration as a generalizable concept to improve existing and develop new Chemical Biology Probes.

physiology↗