The neuropeptide GsMTx4 inhibits a mechanosensitive BK channel through the voltage-dependent modification specific to mechano-gating

Abstract

Edited by Mike Shipston The cardiac mechanosensitive BK (Slo1) channels are gated by Ca 2؉ , voltage, and membrane stretch. The neuropeptide GsMTx4 is a selective inhibitor of mechanosensitive (MS) channels. It has been reported to suppress stretch-induced cardiac fibrillation in the heart, but the mechanism underlying the specificity and even the targeting channel(s) in the heart remain elusive. Here, we report that GsMTx4 inhibits a stretch-activated BK channel (SAKcaC) in the heart through a modulation specific to mechano-gating. We show that membrane stretching increases while GsMTx4 decreases the open probability (P o) of SAKcaC. These effects were mostly abolished by the deletion of the STREX axis-regulated (STREX) exon located between RCK1 and RCK2 domains in BK channels. Single-channel kinetics analysis revealed that membrane stretch activates SAKcaC by prolonging the open-time duration (O) and shortening the closed-time constant (C). In contrast, GsMTx4 reversed the effects of membrane stretch, suggesting that GsMTx4 inhibits SAKcaC activity by interfering with mechano-gating of the channel. Moreover, GsMTx4 exerted stronger efficacy on SAKcaC under membrane-hyperpolarized/resting conditions. Molecular dynamics simulation study revealed that GsMTx4 appeared to have the ability to penetrate deeply within the bilayer, thus generating strong membrane deformation under the hyperpolarizing/resting conditions. Immunostaining results indicate that BK variants containing STREX are also expressed in mouse ventricular cardiomyocytes. Our results provide common mechanisms of peptide actions on MS channels and may give clues to therapeutic suppression of cardiac arrhythmias caused by excitatory currents through MS channels under hyper-mechanical stress in the heart.

Mechanobiology of the brain in ageing and Alzheimer's disease

“…Interestingly, S1P and S1P receptor signalling are known to be involved in axon guidance in the frog optic nerve (Strochlic, Dwivedy, van Horck, Falk, & Holt, 2008). Neurons and glia also express other mechanosensitive channels that open in response to direct forces, such as TRPV4 (upregulated in astrocytes following hypoxic/ischaemic injury) (Butenko et al., 2012), TRPA1 (expressed in layer V pyramidal neurons in the somatosensory cortex) (Kheradpezhouh, Choy, Daria, & Arabzadeh, 2017), TRPC1 (knockout of which abolishes environmental enrichment‐induced neurogenesis in the dentate gyrus) (Du et al., 2017), NMDA receptor (channel gating is modulated by hydrostatic and osmotic pressures and deformations in the cell membrane) (Kloda, Martinac, & Adams, 2007; Paoletti & Ascher, 1994) and Ca 2+ ‐activated potassium (BK) channels (expressed in the outer layers of the cortex and the perforant path fibres projecting to the hippocampus) (Li et al., 2019; Wanner et al., 1999). Table 1 describes some of the receptors and signalling cascades that may be important in CNS mechanosensation.…”

Piezo1 and BKCa channels in human atrial fibroblasts: interplay and remodelling in atrial fibrillation

“…To confirm channel identity, we applied the spider toxin peptide Grammostola spatulata mechanotoxin 4 (GsMTx4) L-isomer (10 μmol/L, H 2 0 as solvent, CSBio, Menlo Park, CA, USA), a known blocker of cation non-selective SAC, including Piezo1 41 and potassium-selective ion channels such as BK Ca . 42 The holding voltage for all experiments was −80 mV when recording Piezo1. Current-pressure curves were fitted with a standard Boltzmann function , where I max is the highest value of current during a pressure pulse, I min is the lowest one, and P 0.5 is the pressure required to obtain half-maximal activation and k is the time constant.…”

Mechanical and chemical activation of GPR68 probed with a genetically encoded fluorescent reporter

“…Acute incubation with micromolar concentrations of the small spider toxin GsMTx4 inhibits activation of certain mechanosensitive ion channels by membrane stretch, FSS and mechanical indentation (Alcaino et al, 2017;Bae et al, 2011;Jetta et al, 2019;Li et al, 2019;Suchyna et al, 2004). In addition, GsMTx4 also reduces the activity of the membrane motor prestin (Fang and Iwasa, 2006)…”