Biology subjects

Wirth, J. O.

Publications and source records attributed to Wirth, J. O..

5 recordsLinked to original sources

bioRxiv2025

CLUSTERING DYNAMICALLY MODULATE THE BIOPHYSICS OF VOLTAGE-GATED SODIUM CHANNELS: HOW NANOSCALE PHENOMENA DETERMINE HEALTH AND DISEASE

Precise regulation of ion channel biophysics is an essential life process that governs electrical signaling in excitable tissues. Many ion channels including voltage-gated Na+ channels (NaVs) exist in the membrane as clusters, which show distinct biophysical behavior not predicted by single-channel measurements. In both heterologous and native systems, we report that single-channel-based predictions significantly overestimated Na+ current (INa) amplitudes from multi-channel clusters. Computational modeling suggested that these observations could reflect interactions between adjacent channels, such as recently reported between NaVs, and identified specific biophysical consequences thereof. This updated model not only accurately predicted behaviors observed from NaV clusters and consequent cellular physiology, but also suggested the possibility that clustered NaVs may respond differently to use-dependent pharmacological agents. Experiments validated the latter prediction and further identified modulation of clustering as a novel approach to correcting macroscopic electrophysiological dysfunction resulting from NaV defects linked to life-threatening arrhythmias and seizures. Thus, our study not only motivates a fundamental revision of how ion channels behave when clustered but also highlights resulting biophysical effects as important considerations for pharmacology and a potential therapeutic target to address human disease.

physiology↗

bioRxiv2025

A Two-Heads-Bound State Drives KIF1A Superprocessivity

KIF1A, a neuron-specific Kinesin-3 motor, is indispensable for long-distance axonal transport and nuclear migration, processes vital for neuronal function. Using MINFLUX tracking, we reveal that KIF1A predominantly adopts a two-heads-bound state, even under ATP-limiting conditions, challenging prior models proposing a one-head-bound rate-limiting step. This two-heads-bound conformation, stabilized by interactions between the positively charged K-loop and negatively charged tubulin tails, enhances microtubule affinity and minimizes detachment. The shorter neck linker facilitates inter-head tension, keeping the heads out of phase and enabling highly coordinated stepping. In contrast, Kinesin-1 (KIF5B) transitions to a one-head-bound state under similar conditions, limiting its processivity. Perturbing KIF1As mechanochemical cycle by prolonging its one-head-bound state significantly reduces processivity, underscoring the critical role of the two-heads-bound state in motility. These findings establish a mechanistic framework for understanding KIF1As adaptations for neuronal transport and dysfunction in neurological diseases.

biophysics↗

bioRxiv2024

Dual-color MINFLUX: Kinesin-1 takes Chasse-Inchworm steps

Withdrawal statementThe authors have withdrawn this manuscript because refined experiments with a remodeled two-color MINFLUX setup featuring improved accuracy and precision of the two-color registration, do not support the reported Chasse-Inchworm stepping mechanism of kinesin-1. The Chasse-Inchworm mechanism was postulated based on recurrent observations of separations of 0 and 16 nanometers between a green-absorbing and a red-absorbing fluorophore, each respectively attached to the two motor domains of kinesin-1. However, the same experiments performed with the improved two-color MINFLUX setup revealed merely separations of 0 and 8 nanometers, aligning with the widely accepted hand-over-hand mechanism. Since the authors no longer stand behind their initial conclusions, they do not wish this work to be cited as a reference. In case of questions, please contact the corresponding author.

biophysics↗

bioRxiv2024

Diffraction minima resolve point scatterers at tiny fractions (1/80) of the wavelength

Discerning two or more identical and constantly scattering point sources using freely propagating waves is thought to be limited by diffraction. Here we show both theoretically and experimentally that by employing a diffraction minimum rather than a maximum for resolution, a given number of point scatterers can be discerned at tiny fractions of the employed wavelength. Specifically, we identify an 8 nm distance between two constantly emitting (non-blinking, non-switchable) fluorescent molecules, corresponding to 1/80 of the wavelength. Moreover, we show that contrary to naive expectations, the measurement precision improves with decreasing distance between the scatterers and with increased scatterer density, thus opening up the prospect of resolving clusters of (optical) point scatterers at tiny fractions of the wavelength.

biophysics↗

bioRxiv2023

Uncovering kinesin dynamics in neurites with MINFLUX

Neurons grow neurites of several tens of micrometers in length, necessitating active transport from the cell body by motor proteins. By tracking fluorophores as minimally invasive labels, MINFLUX is able to quantify the motion of those proteins with nanometer/millisecond resolution. Here we study the substeps of a truncated kinesin-1 mutant in primary rat hippocampal neurons, which have so far been mainly observed on microtubules polymerized on glass coverslips. A gentle fixation protocol largely maintains the structure and surface modifications of the microtubules in the cell. By analyzing the time between the substeps, we identify the ATP-binding state of kinesin-1 and observe the associated rotation of the kinesin-1 head in neurites. We also observed kinesin-1 switching microtubules mid-walk, highlighting the potential of MINFLUX to study the details of active cellular transport.

biophysics↗