ORCID Profile
0000-0003-1192-0403
Current Organisations
University of Queensland Institute for Molecular Bioscience
,
Ouranos Inc
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Publisher: Elsevier BV
Date: 05-2009
DOI: 10.1016/J.CECA.2009.03.006
Abstract: Calcium signaling in myocytes is dependent on the cardiac ryanodine receptor (RyR2) calcium release channel and the calcium buffering protein in the sarcoplasmic reticulum, cardiac calsequestrin (CSQ2). The overall properties of CSQ2 and its regulation of RyR2 have not been explored in detail or directly compared with skeletal CSQ1 and its regulation of the skeletal RyR1, with physiological ionic strength and Ca(2+) concentrations. We find that there are major differences between the two isoforms under these physiological conditions. Ca(2+) binding to CSQ2 is 50% lower than to CSQ1. Only approximately 30% of CSQ2 is bound to cardiac junctional face membrane (JFM), compared with approximately 70% of CSQ1 and the ratio of CSQ2 to RyR2 is only 50% of the CSQ1/RyR1 ratio. Chemical crosslinking shows that CSQ2 is mostly monomer/dimer, while CSQ1 is mostly polymerized. In single channel lipid bilayer experiments, CSQ2 monomers and/or dimers increase the open probability of both RyR1 and RyR2 channels, while CSQ1 polymers decrease the activity of RyR1. We speculate that CSQ2 facilitates high rates of Ca(2+) release through RyR2 during systole, while CSQ1 curtails RyR1 opening in response to a single action potential to maintain Ca(2+) and allow repeated Ca(2+) release and graded activation with increased stimulation frequency.
Publisher: Springer Science and Business Media LLC
Date: 29-01-2015
Publisher: Elsevier BV
Date: 02-2019
Publisher: Elsevier
Date: 2016
Publisher: The Company of Biologists
Date: 2014
DOI: 10.1242/JCS.156760
Abstract: We report the impact of redox potential on isolated cardiac ryanodine receptor (RyR2) channel activity and its response to physiological changes in luminal [Ca2+]. Basal leak from the sarcoplasmic reticulum (SR) is required for normal Ca2+ handling, but excess diastolic Ca2+ leak attributed to oxidative stress is thought to lower RyR2 threshold for spontaneous SR Ca2+ release to induce arrhythmia in pathological situations. Therefore we examined RyR2 response to luminal [Ca2+] under reducing or oxidising cytoplasmic redox conditions. Unexpectedly as luminal [Ca2+] increased from 0.1–1.5 mM RyR2 activity declined when pretreated with cytoplasmic 1 mM DTT, or GSH∶GSSG buffered to a “healthy” reduced cytoplasmic redox potential (−220 mV). Conversely, with 20 µM cytoplasmic 4,4′-DTDP, or redox buffered to an oxidising −180 mV, RyR2 activity increased with increasing luminal [Ca2+]. The luminal redox potential was constant at −180 mV in each case. These responses to luminal Ca2+ were maintained with 2 mM Na2ATP or 5 mM MgATP (1 mM free Mg2+). Overall the results suggest that the redox potential in the RyR2 junctional microdomain is normally more oxidised than the bulk cytoplasm.
Publisher: Springer Science and Business Media LLC
Date: 06-01-2021
Publisher: Springer Science and Business Media LLC
Date: 16-11-2020
DOI: 10.1186/S13395-020-00250-5
Abstract: Manual analysis of cross-sectional area, fiber-type distribution, and total and centralized nuclei in skeletal muscle cross sections is tedious and time consuming, necessitating an accurate, automated method of analysis. While several excellent programs are available, our analyses of skeletal muscle disease models suggest the need for additional features and flexibility to adequately describe disease pathology. We introduce a new semi-automated analysis program, MyoSight, which is designed to facilitate image analysis of skeletal muscle cross sections and provide additional flexibility in the analyses. We describe staining and imaging methods that generate high-quality images of immunofluorescent-labelled cross sections from mouse skeletal muscle. Using these methods, we can analyze up to 5 different fluorophores in a single image, allowing simultaneous analyses of perinuclei, central nuclei, fiber size, and fiber-type distribution. MyoSight displays high reproducibility among users, and the data generated are in close agreement with data obtained from manual analyses of cross-sectional area (CSA), fiber number, fiber-type distribution, and number and localization of myonuclei. Furthermore, MyoSight clearly delineates changes in these parameters in muscle sections from a mouse model of Duchenne muscular dystrophy (mdx). MyoSight is a new program based on an algorithm that can be optimized by the user to obtain highly accurate fiber size, fiber-type identification, and perinuclei and central nuclei per fiber measurements. MyoSight combines features available separately in other programs, is user friendly, and provides visual outputs that allow the user to confirm the accuracy of the analyses and correct any inaccuracies. We present MyoSight as a new program to facilitate the analyses of fiber type and CSA changes arising from injury, disease, exercise, and therapeutic interventions.
Publisher: Springer Science and Business Media LLC
Date: 24-03-2017
DOI: 10.1038/NCOMMS14659
Abstract: Mutations in the RYR1 gene cause severe myopathies. Mice with an I4895T mutation in the type 1 ryanodine receptor/Ca 2+ release channel (RyR1) display muscle weakness and atrophy, but the underlying mechanisms are unclear. Here we show that the I4895T mutation in RyR1 decreases the litude of the sarcoplasmic reticulum (SR) Ca 2+ transient, resting cytosolic Ca 2+ levels, muscle triadin content and calsequestrin (CSQ) localization to the junctional SR, and increases endoplasmic reticulum (ER) stress/unfolded protein response (UPR) and mitochondrial ROS production. Treatment of mice carrying the I4895T mutation with a chemical chaperone, sodium 4-phenylbutyrate (4PBA), reduces ER stress/UPR and improves muscle function, but does not restore SR Ca 2+ transients in I4895T fibres to wild type levels, suggesting that decreased SR Ca 2+ release is not the major driver of the myopathy. These findings suggest that 4PBA, an FDA-approved drug, has potential as a therapeutic intervention for RyR1 myopathies that are associated with ER stress.
Publisher: The Open Journal
Date: 18-05-2023
DOI: 10.21105/JOSS.05415
Publisher: Oxford University Press (OUP)
Date: 09-01-2015
DOI: 10.1093/HMG/DDV003
Publisher: Wiley
Date: 30-03-2021
Publisher: Wiley
Date: 23-04-2012
DOI: 10.1111/J.1440-1681.2012.05704.X
Abstract: The contractile function of the heart requires the release of Ca(2+) from intracellular Ca(2+) stores in the sarcoplasmic reticulum (SR) of cardiac muscle cells. The efficacy of Ca(2+) release depends on the amount of Ca(2+) loaded into the Ca(2+) store and the way in which this 'Ca(2+) load' influences the activity of the cardiac ryanodine receptor Ca(2+) release channel (RyR2). The effects of the Ca(2+) load on Ca(2+) release through RyR2 are facilitated by: (i) the sensitivity of RyR2 itself to luminal Ca(2+) concentrations and (ii) interactions between the cardiac Ca(2+) -binding protein calsequestrin (CSQ) 2 and RyR2, transmitted through the 'anchoring' proteins junctin and/or triadin. Mutations in RyR2 are linked to catecholaminergic polymorphic ventricular tachycardia (CPVT) and sudden cardiac death. The tachycardia is associated with changes in the sensitivity of RyR2 to luminal Ca(2+) . Triadin-, junctin- or CSQ-null animals survive, but their longevity and ability to tolerate stress is compromised. These studies reveal the importance of the proteins in normal muscle function, but do not reveal the molecular nature of their functional interactions, which must be defined before changes in the proteins leading to CPVT and heart disease can be understood. Herein, we discuss known interactions between the RyR, triadin, junctin and CSQ with emphasis on the cardiac isoforms of the proteins. Where there is little known about the cardiac isoforms, we discuss evidence from skeletal isoforms.
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 08-08-2014
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 22-06-2011
Abstract: Our aim was to examine the molecular basis for acute effects of the anthracycline daunorubicin on cardiac ryanodine receptor (RyR2) channels and cardiac calsequestrin (CSQ2). Cardiotoxic effects of anthracyclines preclude their chemotherapeutic use in patients with pre-existing heart conditions. To address this significant problem, the mechanisms of anthracycline toxicity must be defined but at present are poorly understood. RyR2 channel activity was assessed by measuring Ca²⁺ release from cardiac sarcoplasmic reticulum vesicles and by examining single RyR2 channels inserted into artificial lipid bilayers. We show that 0.5 to 10 μM daunorubicin increases the activity of RyR2 channels after 5 to 10 min and that activity then declines to very low levels when channels are exposed to daunorubicin concentrations of ≥ 2.5 μM for a further 10 to 20 min. Extensive dissection of these effects shows for the first time that the activation results from a redox-independent binding of daunorubicin to the RyR2 complex. Novel data include the demonstration of daunorubicin binding to RyR2. We provide compelling evidence that RyR2 channel inhibition is due to the oxidation of free SH groups. The oxidation reaction is prevented by the presence of 1 mM dithiothreitol. We also present novel data showing that CSQ2 modifies the response of RyR2 to daunorubicin, but that the response of RyR2 is not dependent on daunorubicin binding to CSQ2. We suggest that binding of daunorubicin to RyR2 and CSQ2, and oxidation of RyR2, are all likely to contribute to anthracycline-induced cardiotoxicity during chemotherapy.
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 15-09-2017
Abstract: The chemotherapeutic anthracycline metabolite doxorubicinol (doxOL) has been shown to interact with and disrupt the function of the cardiac ryanodine receptor Ca
Publisher: Rockefeller University Press
Date: 30-07-2012
Publisher: Elsevier BV
Date: 09-2014
Publisher: Springer Science and Business Media LLC
Date: 09-10-2020
DOI: 10.1038/S41467-020-18865-Z
Abstract: Mutations in the skeletal muscle Ca 2+ release channel, the type 1 ryanodine receptor (RYR1), cause malignant hyperthermia susceptibility (MHS) and a life-threatening sensitivity to heat, which is most severe in children. Mice with an MHS-associated mutation in Ryr1 (Y524S, YS) display lethal muscle contractures in response to heat. Here we show that the heat response in the YS mice is exacerbated by brown fat adaptive thermogenesis. In addition, the YS mice have more brown adipose tissue thermogenic capacity than their littermate controls. Blood lactate levels are elevated in both heat-sensitive MHS patients with RYR1 mutations and YS mice due to Ca 2+ driven increases in muscle metabolism. Lactate increases brown adipogenesis in both mouse and human brown preadipocytes. This study suggests that simple lifestyle modifications such as avoiding extreme temperatures and maintaining thermoneutrality could decrease the risk of life-threatening responses to heat and exercise in in iduals with RYR1 pathogenic variants.
Location: Australia
No related grants have been discovered for Pascal Bourgault.