Biology subjects

Wijerathne, T. D.

Publications and source records attributed to Wijerathne, T. D..

3 recordsLinked to original sources

bioRxiv2025

A two-step clockwork mechanism opens a proteo-lipidic pore in PIEZO2 channels

Mechanosensitive PIEZO channels are thought to open their pore through tension-induced flattening of large transmembrane arm domains. Yet, the structural basis of this activation remains unclear. Here, we uncover the conformational coupling between arm flattening and pore opening in PIEZO2 by capturing protein motions across length scales using hybrid-resolution molecular dynamics simulations. Sampling multiple microsecond-long trajectories under physiological activation tension show that arm flattening correlates with anticlockwise rotation of the pore domain and with clockwise twisting of inner pore helices, enabling dilation and hydration of a transmembrane pore gate. These clockwork motions enable PIEZO2 to populate two open states with distinct conductance depending on applied membrane tension, in agreement with single-channel electrophysiology. Pore opening is accompanied by the separation of pore helices, creating interhelical gaps which become filled with lipids, resulting in the fully conducting pore being walled by both lipids and protein. The fully open PIEZO2 state recapitulates minimal pore size, conductance, ion selectivity, and outward rectification of chloride currents observed electrophysiologically. This work reveals how tension-induced large-scale rearrangements of the PIEZO2 arms funnel into subtle and dynamic gating motions, providing invaluable structural insights for future structure-function and drug discovery studies.

biophysics↗

bioRxiv2024

Mammalian PIEZO channels rectify anionic currents

Under physiological conditions, mammalian PIEZO channels (PIEZO1 and PIEZO2) elicit transient currents mostly carried by monovalent and divalent cations. PIEZO1 is also known to permeate chloride ions, with a Cl- / Na+ permeability ratio of about 0.2. Yet, little is known about how anions permeate PIEZO channels. Here, by separately measuring sodium and chloride currents using non-permanent counter-ions, we show that both PIEZO1 and PIEZO2 rectify chloride currents outwardly, favoring entry of chloride ions at voltages above their reversal potential, whereas little to no rectification was observed for sodium currents. Interestingly, chloride currents elicited by 9K, an anion-selective PIEZO1 mutant harboring multiple positive residues along intracellular pore fenestrations, also rectify but in the inward direction. Molecular dynamics simulation indicate that the inward rectification of chloride currents in 9K correlates with the largely positive electrostatic potential at the intracellular pore entrance, suggesting that rectification can be tuned by pore polarity. These results demonstrate that the pore of mammalian PIEZO channels inherently rectifies chloride currents. Statement of significanceMechanosensitive PIEZO ion channels play many important roles across cells and tissues. Their open pore facilitates the flow of cations down their electrochemical gradients, eliciting sodium-driven membrane depolarization and calcium-dependent signaling under physiological conditions. Yet, these channels also permeate chloride ions. In this study, we show that the two mammalian PIEZO channel homologs preferentially permeate chloride ions into the cells at voltages more positive than the chloride reversal potential. Although PIEZOs permeate cations more effectively than chloride ions, the influx of chloride ions mediated by PIEZOs could participate in certain physiological processes.

biophysics↗

bioRxiv2022

Rearrangements of Piezo1 blade domains correlate with pore opening

PIEZO1 channels open in response to numerous mechanical stimuli, such as physical membrane deformations, which modulate the curvature of flexible domains called blades. Yet, whether different stimuli cause similar blade motions and whether these rearrangements correlate with pore opening remain unclear. Here, we scan local conformational changes along the PIEZO1 blade using fluorescent probes. We identify two distant probes, one intracellular proximal and the other extracellular distal, which independently and robustly respond to flow stimuli. Flow-induced signals from both probes exquisitely correlate with PIEZO1-dependent calcium influx and specifically increase in presence of fast-inactivating pore mutations. In contrast, both probes remain fluorimetrically silent to hypotonic shocks and indentations, two stimuli that otherwise evoke normal electrochemical responses in both engineered channels. This study reveals that flow-induced blade motions are functionally coupled to the pore and that at least two distant blade regions discriminate flow from two other stimuli, suggesting that PIEZO1 mobilizes distinct mechanisms to sense a broad range of mechanical cues. TeaserFluorimetric evidence suggests that different mechanical stimuli impart distinct rearrangements in PIEZO1s mechanosensory domains.

biophysics↗