Biology subjects

Esch, K.

Publications and source records attributed to Esch, K..

4 recordsLinked to original sources

bioRxiv2025

Structure and function of otoferlin, a synaptic protein of sensory hair cells essential for hearing

Our sense of hearing relies upon speedy synaptic transmission of sound information from cochlear inner hair cells (IHCs) to spiral ganglion neurons (SGNs). To accomplish this, IHCs employ a sophisticated presynaptic machinery including the multi-C2-domain protein otoferlin which is affected by human deafness mutations. Otoferlin is essential for IHC-exocytosis but how it binds Ca2+ and the target membrane to serve synaptic vesicle (SV) tethering, docking and fusion remained unclear. Here, we obtained cryo-electron-microscopy structures of Ca2+-bound otoferlin and employed molecular dynamics simulations of membrane binding. We show that membrane binding involves C2B-C2G-domains and repositions C2F- and C2G-domains. Progressive disruption of Ca2+-binding by the C2D-domain in mice increasingly altered synaptic sound encoding and eliminated the Ca2+-cooperativity of SV-exocytosis, indicating that this Ca2+-cooperativity reflects binding of several Ca2+-ions to otoferlin. Together, our findings elucidate molecular mechanisms underlying otoferlin-mediated SV-docking and support a role of otoferlin as Ca2+-sensor of SV-fusion in IHCs.

neuroscience↗

bioRxiv2025

Stimulus-induced mechanical compaction of biological polymer networks via smart hydrogel microstructures

The remodeling of the extracellular matrix by mechanical forces plays a crucial role in organizing cellular microenvironments. To study these mechanical perturbations, various methods have been developed to modify the cellular microenvironment and to apply controlled forces. However, most existing approaches rely either on instruments that cannot be integrated into lab-on-chip systems or on small probes with limited spatiotemporal precision. Here, we present a lab-on-chip system that enables spatially and temporally controlled mechanical perturbations of biological polymer networks. First, we fabricated thermoresponsive hydrogel microstructures within flow chambers and optimized their material composition and photopolymerization parameters. Second, we demonstrated the temporally controlled compression of Matrigel and collagen networks through temperature-stimulated expansion of the hydrogel microstructures. Following compression, Matrigel was plastically deformed, whereas the collagen network relaxed elastically. Finally, we showed that the compression of collagen networks can be spatially modulated by integrating hydrogel structures responsive to light stimuli. By mimicking the dynamic behavior of cells that remodel biological polymer networks, our method provides a versatile platform for future studies on extracellular matrix remodeling and the effects of mechanical forces on cellular microenvironments in both physiological and pathological contexts.

bioengineering↗

bioRxiv2025

Lithographic structuring of thermoresponsive hydrogel on a micron scale

Hydrogel microstructures and microchannels are important tools in biophysical bottom-up approaches for studying the interactions between extracellular obstacles or boundaries and cells. In prior studies, several microstructuring techniques, cell sources, and gel types have been employed to mimic static cellular environments. However, the dynamic nature of the extracellular environment, which exerts forces on cells, plays an important role in tissue-level contexts. To date, only few approaches have been implemenmted to mimic these forces of the extracellular environment. Here, we present an approach for generating arrays of hydrogel microstructures, that expand and contract dynamically in response to temperature modulations. To do this, we use a thermoresponsive hydrogel and a custom-built lithographic setup. Through direct lithographic photopatterning of a liquid phase, we fabricate smart hydrogel microstructures at the micrometer scale (10-100 m) with well-defined geometries. These hydrogel microstructures display reversible size changes of over 70% triggered by temperature modulations. Our study represents a step towards mimicking the dynamic properties of biological boundaries and obstacles. The dynamic nature of smart hydrogel microstructures holds the potential to mimic the micron-scale dynamics of extracellular environments. Our results may thus be relevant for the fields of bioengineering and systems level biophysics offering opportunities for manipulating and exploring cellular interactions with dynamic obstacles.

bioengineering↗

bioRxiv2024

Controlled Protein-Membrane Interactions Regulate Self-Organization of Min Protein Patterns

Self-organizing protein patterns play an essential role in life, governing important cellular processes, such as polarization and division. While the field of protein self-organization has reached a point where basic pattern-forming mechanisms can be reconstituted in vitro using purified proteins, understanding how cells can dynamically switch and modulate these patterns, especially when transiently needed, remains an interesting frontier. Here, we demonstrate the efficient regulation of self-organizing protein patterns through modulation of simple biophysical membrane parameters. Our investigation focusses on the impact of membrane affinity changes on Min protein patterns at lipid membranes composed of E. coli lipids or minimal lipid composition and we present three major results. First, we observed the emergence of a diverse array of pattern phenotypes, ranging from waves to snowflake-like structures. Second, we establish the dependency of these patterns on the density of protein-membrane linkers. Finally, we demonstrate the fine-tuning of snow-flake-like patterns by regulating membrane charge through lipid composition. Our results demonstrate the significant influence of membrane linkage as a straightforward biophysical parameter governing protein pattern formation. Our research points towards a simple yet intriguing mechanism by which cells can adeptly tune and switch protein patterns on the mesoscale.

biophysics↗