Ionic Selectivity and Permeation Properties of Human PIEZO1 Channels

Abstract

Members of the eukaryotic PIEZO family (the human orthologs are noted hPIEZO1 and hPIEZO2) form cation-selective mechanically-gated channels. We characterized the selectivity of human PIEZO1 (hPIEZO1) for alkali ions: K+, Na+, Cs+ and Li+; organic cations: TMA and TEA, and divalents: Ba2+, Ca2+, Mg2+ and Mn2+. All monovalent ions permeated the channel. At a membrane potential of -100 mV, Cs+, Na+ and K+ had chord conductances in the range of 35–55 pS with the exception of Li+, which had a significantly lower conductance of ~ 23 pS. The divalents decreased the single-channel permeability of K+, presumably because the divalents permeated slowly and occupied the open channel for a significant fraction of the time. In cell-attached mode, 90 mM extracellular divalents had a conductance for inward currents carried by the divalents of: 25 pS for Ba2+ and 15 pS for Ca2+ at -80 mV and 10 pS for Mg2+ at -50 mV. The organic cations, TMA and TEA, permeated slowly and attenuated K+ currents much like the divalents. As expected, the channel K+ conductance increased with K+ concentration saturating at ~ 45 pS and the KD of K+ for the channel was 32 mM. Pure divalent ion currents were of lower amplitude than those with alkali ions and the channel opening rate was lower in the presence of divalents than in the presence of monovalents. Exposing cells to the actin disrupting reagent cytochalasin D increased the frequency of openings in cell-attached patches probably by reducing mechanoprotection.

The circulatory physiopathology of human red blood cells investigated with a multiplatform model of cellular homeostasis. II. Capillary transits and the role of PIEZO1

“…From the start, it was critical to select the body of knowledge we wished the model outcomes to comply with, and to establish a hierarchical scale of weight for the different parameters based on experimental support and relevance. The experimental data chosen to constrain and guide this investigation was primarily based on relatively recent results by Dyrda et al, (27), Glogowska et al, (38), Danielczok et al, (35), Kuchel and Shishmarev, (34), Zhao et al, (36) Ganansambandam et al, (39), and also on dated results that harmonize with the more recent findings (40)(41)(42). Five PIEZO1-attributed parameters defined the model protocol for single capillary transit simulations: duration of the open-state (OS, in s), three cationic permeabilities for Ca 2+ , Na + and K + , PzCa, PzNa, PzK, respectively (in h -1 ), and one anionic permeability for the combined diffusible Cl -+ HCO 3 anions, PzA (h -1 ).…”

Mechanical transduction by ion channels: A cautionary tale

“…You cannot depend upon channel conductance alone [57] as a sound marker of expressed channels since it is easy to find situations in which the environment: cell-attached patch, inside-out or outside-out patch, or whole-cell, or planar bilayer have different conductances [66,177] . You would want a channel with big differences in selectivity, ideally a change from cation to anion selectivity!…”

Inhibition of Piezo1 attenuates demyelination in the central nervous system

“…Piezo1 is a mechanically gated cation channel and allows the influx of calcium ions (Ca 2+ ) into the cell when activated by mechanical cues (Gnanasambandam et al, 2017;Gnanasambandam, Bae, Gottlieb, & Sachs, 2015). PIEZO proteins are highly conserved throughout evolution and play crucial roles in mechanosensation and mechanotransduction in multicellular organisms (Coste et al, 2012).…”

“…Piezo1 proteins (>2,500 amino acids)(Coste et al, 2010(Coste et al, , 2012 trimerize to form nonselective cation channels(Gnanasambandam et al, 2015) with extracellular mechanosensing "propeller blades" that facilitate the mechanogating mechanism of the ion channel(Zhao, Zhou, Li, & Xiao, 2018). Traction force-mediated activation of Piezo1 channels in neural stem cells causes Ca 2+ influx, resulting in nuclear localization of the mechanoresponsive transcriptional coactivators yes-associated protein (Yap) and transcriptional coactivator with PDZbinding motif (Taz)(Pathak et al, 2014).…”