Biology subjects

Docter, T.

Publications and source records attributed to Docter, T..

4 recordsLinked to original sources

bioRxiv2025

Structural basis for proton inhibition of the two-pore domain K+ channel TASK-1

TASK-1 is a pH-sensitive two-pore domain K+ channel inhibited by external protons. TASK-1 is widely expressed, including in cardiomyocytes and chemosensitive neurons in the brain. Altered channel expression and activity are implicated in diseases including atrial fibrillation, pulmonary arterial hypertension, and developmental delay with sleep apnea. Structures of TASK-1 have been captured with an open external and closed internal gate. The structural basis for external proton inhibition and potential for communication between inner and outer gates are incompletely understood. Here, we determine a cryo-EM structure of TASK-1 at low pH with a closed extracellular gate and assess pH sensitivity of mutated channels. Proton inhibition of TASK-1 involves a C-type selectivity filter gate similar to TASK-3, but distinct from other proton-inhibited K2Ps TASK-2 and TWIK-1. Protonation of an extracellular histidine leads to formation of a hydrophobic seal above the selectivity filter and dilation of the outer two K+ coordination sites to close the channel pore. We find that a pulmonary arterial hypertension-associated loss-of-function mutation near the outer gate increases proton sensitivity, while gain-of-function mutations near the inner X-gate and intracellular cavity reduce proton sensitivity. These data reveal the structural basis for extracellular pH-gating of TASK-1, suggest allosteric communication between the inner and outer gates, and illustrate differences in C-type gating among related K+ channels.

biophysics↗

bioRxiv2024

Cannabinoid inhibition of mechanosensitive K+ channels

Cannabidiol (CBD) is a prominent non-psychoactive small molecule produced by cannabis plants used clinically as an antiepileptic. Here, we show CBD and other cannabinoids are potent inhibitors of mechanosensitive two-pore domain K+ (K2P) channels, including TRAAK and TREK-1 that contribute to spike propagation in myelinated axons. Five TRAAK mutations that cause epilepsy or the neurodevelopmental syndrome FHEIG (facial dysmorphism, hypertrichosis, epilepsy, intellectual/developmental delay, and gingival overgrowth) retain sensitivity to cannabinoid inhibition. A cryo-EM structure reveals CBD binds in the intracellular cavity of TREK-1 to sterically block ion conduction. These results show that cannabinoids and endogenous lipids compete for a common binding site to inhibit channel activity, identify mechanosensitive K2Ps as potential physiological targets of CBD, and suggest cannabinoids could counter gain-of-function in TRAAK channelopathies. SummaryWe discover cannabinoids inhibit mechanosensitive K+ channels including mutants that cause disease and reveal the mechanism for channel block.

neuroscience↗

bioRxiv2023

Pressure and ultrasound activate mechanosensitive TRAAK K+ channels through increased membrane tension

TRAAK is a mechanosensitive two-pore domain K+ (K2P) channel found in nodes of Ranvier within myelinated axons. It displays low leak activity at rest and is activated up to one hundred-fold by increased membrane tension. Structural and functional studies have led to physical models for channel gating and mechanosensitivity, but no quantitative analysis of channel activation by tension has been reported. Here, we use simultaneous patch-clamp recording and fluorescent imaging to determine the tension response characteristics of TRAAK. TRAAK shows high sensitivity and a broad response to tension spanning nearly the entire physiologically relevant tension range. This graded response profile distinguishes TRAAK from similarly low-threshold mechanosensitive channels Piezo1 and MscS, which activate in a step-like fashion over a narrow tension range. We further use patch imaging to show that ultrasonic activation of TRAAK and MscS is due to increased membrane tension. Together, these results provide mechanistic insight into TRAAK tension gating, a framework for exploring the role of mechanosensitive K+ channels at nodes of Ranvier, and biophysical context for developing ultrasound as a mechanical stimulation technique for neuromodulation.

biophysics↗

bioRxiv2020

USH2A is a Meissner corpuscle end-organ protein necessary for vibration sensing in mice and humans

Fingertip mechanoreceptors comprise sensory neuron endings together with specialized skin cells that form the end-organ. Exquisitely sensitive vibration-sensing neurons are associated with Meissners corpuscles and Pacinian corpuscles1. Such end-organ structures have been recognized for more than 160 years, but their exact functions have remained a matter of speculation. Here we examined the role of USH2A in touch sensation in humans and mice. The USH2A gene encodes a transmembrane protein with a very large extracellular domain. Pathogenic USH2A mutations cause Usher syndrome associated with hearing loss and visual impairment2. We show that patients with biallelic pathogenic USH2A mutations also have profound impairments in vibrotactile touch perception. Similarly, mice lacking the USH2A protein showed severe deficits in a forepaw vibrotactile discrimination task. Forepaw rapidly-adapting mechanoreceptors (RAMs) recorded from Ush2a-/- mice innervating Meissners corpuscles showed profound reductions in their vibration sensitivity. However, the USH2A protein was not expressed in sensory neurons, but was found in specialized terminal Schwann cells in Meissners corpuscles. Loss of this large extracellular tether-like protein in corpuscular end-organs innervated by RAMs was sufficient to reduce the vibration sensitivity of mechanoreceptors. Thus, USH2A expressed in corpuscular end-organs associated with vibration sensing is required to properly perceive vibration. We propose that cells within the corpuscle present a tether-like protein that may link to mechanosensitive channels in sensory endings to facilitate small amplitude vibration detection essential for the perception of fine textured surfaces.

neuroscience↗