Dataset Information

Anomalous K_v 7 channel activity in human malignant hyperthermia syndrome unmasks a key role for H₂ S and persulfidation in skeletal muscle.

ABSTRACT:

Background and purpose

Human malignant hyperthermia (MH) syndrome is induced by volatile anaesthetics and involves increased levels of cystathionine β-synthase (CBS)-derived H₂ S within skeletal muscle. This increase contributes to skeletal muscle hypercontractility. K_v 7 channels, expressed in skeletal muscle, may be a molecular target for H₂ S. Here, we have investigated the role of K_v 7 channels in MH.

Experimental approach

Skeletal muscle biopsies were obtained from MH-susceptible (MHS) and MH-negative (MHN) patients. Immunohistochemistry, RT-PCR, Western blot, and in vitro contracture test (IVCT) were carried out. Development and characterization of primary human skeletal muscle cells (PHSKMC) and evaluation of cell membrane potential were also performed. The persulfidation state of K_v 7 channels and polysulfide levels were measured.

Key results

K_v 7 channels were similarly expressed in MHN and MHS biopsies. The IVCT revealed an anomalous contractility of MHS biopsies following exposure to the K_v 7 channel opener retigabine. Incubation of negative biopsies with NaHS, prior to retigabine addition, led to an MHS-like positive response. MHS-derived PHSKMC challenged with retigabine showed a paradoxical depolarizing effect, compared with the canonical hyperpolarizing effect. CBS expression and activity were increased in MHS biopsies, resulting in a major polysulfide bioavailability. Persulfidation of K_v 7.4 channels was significantly higher in MHS than in MHN biopsies.

Conclusions and implications

In skeletal muscle of MHS patients, CBS-derived H₂ S induced persulfidation of K_v 7 channels. This post-translational modification switches the hyperpolarizing activity into depolarizing. This mechanism can contribute to the pathological skeletal muscle hypercontractility typical of MH syndrome.

Linked articles

This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc.

SUBMITTER: Vellecco V

PROVIDER: S-EPMC7024712 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Anomalous K<sub>v</sub> 7 channel activity in human malignant hyperthermia syndrome unmasks a key role for H<sub>2</sub> S and persulfidation in skeletal muscle.

Vellecco Valentina V Martelli Alma A Bibli Iris Sofia IS Vallifuoco Marianna M Manzo Onorina L OL Panza Elisabetta E Citi Valentina V Calderone Vincenzo V de Dominicis Gianfranco G Cozzolino Caterina C Basso Elisabetta M EM Mariniello Martina M Fleming Ingrid I Mancini Antonio A Bucci Mariarosaria M Cirino Giuseppe G

British journal of pharmacology 20190503 4

<h4>Background and purpose</h4>Human malignant hyperthermia (MH) syndrome is induced by volatile anaesthetics and involves increased levels of cystathionine β-synthase (CBS)-derived H<sub>2</sub> S within skeletal muscle. This increase contributes to skeletal muscle hypercontractility. K<sub>v</sub> 7 channels, expressed in skeletal muscle, may be a molecular target for H<sub>2</sub> S. Here, we have investigated the role of K<sub>v</sub> 7 channels in MH.<h4>Experimental approach</h4>Skeletal m ...[more]

PMID: 31051045

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Project description:Malignant hyperthermia susceptibility (MHS) is primarily conferred by mutations within ryanodine receptor type 1 (RYR1). Here we address how the MHS mutation T4826I within the S4-S5 linker influences excitation-contraction coupling and resting myoplasmic Ca(2+) concentration ([Ca(2+)](rest)) in flexor digitorum brevis (FDB) and vastus lateralis prepared from heterozygous (Het) and homozygous (Hom) T4826I-RYR1 knock-in mice (Yuen, B. T., Boncompagni, S., Feng, W., Yang, T., Lopez, J. R., Matthaei, K. I., Goth, S. R., Protasi, F., Franzini-Armstrong, C., Allen, P. D., and Pessah, I. N. (2011) FASEB J. doi:22131268). FDB responses to electrical stimuli and acute halothane (0.1%, v/v) exposure showed a rank order of Hom ≫ Het ≫ WT. Release of Ca(2+) from the sarcoplasmic reticulum and Ca(2+) entry contributed to halothane-triggered increases in [Ca(2+)](rest) in Hom FDBs and elicited pronounced Ca(2+) oscillations in ∼30% of FDBs tested. Genotype contributed significantly elevated [Ca(2+)](rest) (Hom > Het > WT) measured in vivo using ion-selective microelectrodes. Het and Hom oxygen consumption rates measured in intact myotubes using the Seahorse Bioscience (Billerica, MA) flux analyzer and mitochondrial content measured with MitoTracker were lower than WT, whereas total cellular calpain activity was higher than WT. Muscle membranes did not differ in RYR1 expression nor in Ser(2844) phosphorylation among the genotypes. Single channel analysis showed highly divergent gating behavior with Hom and WT favoring open and closed states, respectively, whereas Het exhibited heterogeneous gating behaviors. [(3)H]Ryanodine binding analysis revealed a gene dose influence on binding density and regulation by Ca(2+), Mg(2+), and temperature. Pronounced abnormalities inherent in T4826I-RYR1 channels confer MHS and promote basal disturbances of excitation-contraction coupling, [Ca(2+)](rest), and oxygen consumption rates. Considering that both Het and Hom T4826I-RYR1 mice are viable, the remarkable isolated single channel dysfunction mediated through this mutation in S4-S5 cytoplasmic linker must be highly regulated in vivo.

Project description:BackgroundSkeletal muscle fibres contain transverse tubular (t-tubule) networks that allow electrical signals to rapidly propagate into the fibre. These electrical signals are generated by the transport of ions across the t-tubule membranes and this can result in significant changes in ion concentrations within the t-tubules during muscle excitation. During periods of repeated high-frequency activation of skeletal muscle the t-tubule K+ concentration is believed to increase significantly and diffusive K+ transport from the t-tubules into the interstitial space provides a mechanism for alleviating muscle membrane depolarization. However, the tortuous nature of the highly branched space-filling t-tubule network impedes the diffusion of material through the network. The effective diffusion coefficient for ions in the t-tubules has been measured to be approximately five times lower than in free solution, which is significantly different from existing theoretical values of the effective diffusion coefficient that range from 2-3 times lower than in free solution. To resolve this discrepancy, in this paper we study the process of diffusion within electron microscope scanned sections of the skeletal muscle t-tubule network using mathematical modelling and computer simulation techniques. Our model includes t-tubule geometry, tautness, hydrodynamic and non-planar network factors.ResultsUsing our model we found that the t-tubule network geometry reduced the K+ diffusion coefficient to 19-27% of its value in free solution, which is consistent with the experimentally observed value of 21% and is significantly smaller than existing theoretical values that range from 32-50%. We also found that diffusion in the t-tubules is anomalous for skeletal muscle fibres with a diameter of less than approximately 10-20 microm as a result of obstructed diffusion. We also observed that the [K+] within the interior of the t-tubule network during high-frequency activation is greater for fibres with a larger diameter. Smaller skeletal muscle fibres are therefore more resistant to membrane depolarization. Because the t-tubule network is anisotropic and inhomogeneous, we also found that the [K+] distribution generated within the network was irregular for fibres of small diameter.ConclusionOur model explains the measured effective diffusion coefficient for ions in skeletal muscle t-tubules.

Dataset Information

Anomalous K_v 7 channel activity in human malignant hyperthermia syndrome unmasks a key role for H₂ S and persulfidation in skeletal muscle.

Background and purpose

Experimental approach

Key results

Conclusions and implications

Linked articles

Publications

Anomalous K<sub>v</sub> 7 channel activity in human malignant hyperthermia syndrome unmasks a key role for H<sub>2</sub> S and persulfidation in skeletal muscle.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Dataset Information

Anomalous Kv 7 channel activity in human malignant hyperthermia syndrome unmasks a key role for H2 S and persulfidation in skeletal muscle.

Background and purpose

Experimental approach

Key results

Conclusions and implications

Linked articles

Publications

Anomalous K<sub>v</sub> 7 channel activity in human malignant hyperthermia syndrome unmasks a key role for H<sub>2</sub> S and persulfidation in skeletal muscle.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Anomalous K_v 7 channel activity in human malignant hyperthermia syndrome unmasks a key role for H₂ S and persulfidation in skeletal muscle.