CardiovascularElectrophysiologyLaboratory

Key Research Areas

• Understanding sudden cardiac death during the “fight or flight” response
• Mechanisms of mitochondrial dysfunction in the familial hypertrophic heart
• Mechanisms of sudden cardiac death in familial hypertrophic cardiomyopathy
• Preventing heart failure associated with muscular dystrophy
• Elucidating structure of the L-type calcium channel

Research Overview

Based in Western Australia, the Cardiovascular Electrophysiology Laboratory led by Professor Livia Hool, is concerned with understanding how alterations in calcium and energetics in the heart lead to sudden cardiac death and heart failure. The main way that calcium moves into heart muscle cells is via a unique channel. The channel is essential to life and controls excitation and contraction in the heart. Scientists in this laboratory are currently designing and optimising treatments to help people suffering from ischemic and hypertrophic cardiomyopathy, as well as heart failure associated with muscular dystrophy.

Muscular dystrophy is a fatal muscle wasting disorder affecting 1 in 3,500 boys. The boys show signs of weakness as infants and are restricted to a wheelchair by the age of 12. Researchers in the Cardiovascular Electrophysiology Laboratory have collaborated with scientists from Murdoch University, to develop a drug therapy to help young boys suffering from muscular dystrophy. The drug was administered to a wheelchair-bound ten year old in the United States as part of a clinical trial and as a result of the therapy the boy was able to run in the Boston Children’s Marathon in June 2014.

There are 5 key projects underway in the Cardiovascular Electrophysiology Laboratory, based in Western Australia:

1. Identifying the molecular mechanism for activation of the L-type Ca2+ channel during the “fight or flight” response

Acute alterations in function of the L-type Ca2+ channel lead to sudden cardiac death. Chronic increases in function of the channel lead to the development of cardiac hypertrophy and failure. Sympathetic stimulation increases calcium influx through the L-type Ca2+ channel as a result of phosphorylation of the channel by PKA and is absolutely required to increase contractility during the “fight or flight” response. However the mechanism for this has remained controversial for 40 years because heterogeneous expression systems used to study responses have resulted in conflicting findings and the use of in vitro cell systems have confounded the findings. We have identified a novel serine required to activate the purified human Ca_v1.2 channel protein by PKA. We will “molecularly reconstruct” the channel from purified Ca_v1.2 protein and confirm the functional role of the serine on the native channel in vitro. Using CRISPR/Cas9 technology we will demonstrate that the site is essential for in vivo channel stimulation by β-adrenergic signalling.

2. Determining therapy to reverse hypertrophy in familial hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy is the leading cause of death in healthy individuals under the age of 40 years with the exception of sudden infant death syndrome. There is currently no treatment that prevents the cardiomyopathy. We have identified a novel mechanism by which the L-type Ca2+ channel regulates mitochondrial function and energetics in the heart that occurs via cytoskeletal proteins. In familial hypertrophic cardiomyopathy the communication between the channel and the mitochondria is altered and the hearts are hypermetabolic. We have targeted the L-type Ca2+ channel with a peptide that prevents the hypermetabolic mitochondrial response. We are designing mutant peptides with increased affinity for the channel to reverse the cardiomyopathy.

3. Elucidating the mechanisms for induction of sudden cardiac death in familial hypertrophic cardiomyopathy

Patients with a mutation in a sarcomeric protein associated with familial hypertrophic cardiomyopathy have an increased risk of sudden cardiac death but the mechanisms for sudden death are poorly understood. We use single cell electrophysiology and fluorescent techniques in myocytes from hearts of murine models of familial hypertrophic cardiomyopathy and iPSC-cardiomyocytes from patients with known mutations to determine mechanisms for arrhythmia.

4. How is force transmitted from membrane to the mitochondria in a myocyte

The mechanisms for the development of hypertrophic cardiomyopathy at the level of the myocyte are not well understood. This project examines the effect of altering the stiffness of substrates on myocyte function in particular calcium regulation and mitochondrial function.

5. Elucidating structure/function of the L-type Ca2+ channel

We are utilising patch clamp electrophysiology in conjunction with CRISPR/Cas9 technology to assess functional consequences of point mutations in the L-type Ca2+ channel responsible for Long QT arrhythmias. In collaboration with Filip van Petegem at the University of British Columbia we use this information to assist with determining the structure of the Cav1.2 protein using NMR and cryoEM studies to inform 3D structure guided drug design.

1. Rossetti G, Ermer J, Stentenbach M, Siira S, Richman TR, Milenkovic D, Perks KL, Hughes L, Jameison E, Xiafukaiti G, Ward N, Takahashi S, Whiley NG, Viola HM, Hool LC, Rackham O, Filipovska A. A common genetic variant of a mitochondrial RNA processing enzyme predisposes to insulin resistance. Science Advances Sep 24;7(39):eabi7514, 2021.
2. Chin, I, Hool LC and Choi Y-S Interrogating Cardiac Muscle Cell Mechanobiology on Polyacrylamide Stiffness Gradient Hydrogels Biomaterials Science Oct 12;9(20):6795-6806; 2021.
3. Solomon T, Filipovska A. Hool LC and Viola HM Preventative therapeutic approaches for hypertrophic cardiomyopathy J Physiology Aug 21. doi: 10.1113/JP279410, 2020.
4. Viola HM, Shah A, Johnstone V, Hodson M and Hool LC. Characterization and validation of a preventative therapy for hypertrophic cardiomyopathy in a murine model of the disease Proc Natl Acad Sci U S A. 2020 Sep 15;117(37):23113-23124.
5. Hotka M, Cagalinec M, Hilber K, Hool L, Boehm S and Kubista H. L-type calcium channel-mediated Ca2+-influx adjusts neuronal mitochondrial function to physiological and pathophysiological conditions. Science Signaling Feb 11;13(618):eaaw6923, 2020.
6. Rudler D, Hughes L, Perks T, Richman T, Kuznetsova I, Ermer J, Abudulai LN, Shearwood A-M, Viola HM, Filipovska A, Hool LC, Siira S, Rackham O and Filipovska A. Fidelity of translation initiation is required for coordinated respiratory complex assembly Science Advances. Dec 20;5(12):eaay2118. doi: 10.1126/sciadv.aay2118, 2019.
7. Ferreira N, Perks K, Rossetti G, Rudler D, Hughes L, Ermer JA, Scott L, Kuznetsova I, Narayana V, Cserne Szappanos H, Tull D, Yeoh G, Hool LC, Filipovska A and Rackham O. Mitochondrial stress signalling and cellular proliferation reverse the effects of mitochondrial mistranslation EMBO J Nov 13:e102155, 2019.
8. Olivé M, Engvall M , Ravenscroft G, Cabrera-Serrano M, Jiao H, Bortolotti CA, Pignataro M, Lambrughi M, Jiang H, Forrest ARR, Benseny-Cases N, Hofbauer S, Obinger C, Battistuzzi G, Bellei M, Borsari M, Di Rocco G, Viola HM, Hool LC, Cladera J, Lagerstedt-Robinson K, Xiang F, Wredenberg A, Miralles M, Baiges JJ, Malfatti E, Romero NB, Streichenberger N, Vial C, Claeys KG, Straathof CSM, Goris A, Freyer C, Lammens M, Bassez G, Kere J, Clemente P, Sejersen T, Udd B, Vidal N, Ferrer I, Edström L, Wedell A and Laing NG. MB mutation impairs oxygen binding and causes myoglobinopathy, an adult-onset autosomal dominant myopathy with characteristic sarcoplasmic inclusions. Nature Communications. Mar 27;10(1):1396, 2019.
9. Siira S, Rossetti G, Richman T, Perks K, Kuznetsova I, Hughes L, Ermer J, Shearwood A-M, Viola H, Hool L, Rackham O and Filipovska A. Concerted regulation of mitochondrial and nuclear non-coding RNAs by a dual-targeted RNase Z EMBO Reports Oct 20. pii: e46198. doi: 10.15252/embr.201846198, 2018.
10. Viola HM, Johnstone V, Adams A, Fletcher S, Hool LC. A morpholino oligomer therapy regime that restores mitochondrial function and prevents mdx cardiomyopathy. JACC Basic to Translational Science Jun 25;3(3):391-402, 2018.
11. Perks K, Rossetti G, Kuznetsova I, Hughes L, Ermer J, Ferreira N, Rudler D, Spahr H, Shearwood A-M, Viola H, Siira S, Hool L, Larsson N, Rackham O, Filipovska A. PTCD1 recruits a pseudouridinylase complex to the mitochondrial 16S rRNA and is essential for mitochondrial ribosome assembly Cell Reports Apr 3;23(1):127-142, 2018.
12. Cserne-Szappanos H, Muralidharan P, Petereit J, Millar H, Ingley E and Hool LC. Identification of a novel cAMP dependent protein kinase A phosphorylation site on the human cardiac calcium channel. Scientific Reports Nov 9;7(1):15118, 2017.
13. Perks KL, Ferreira N, Richman TR, Ermer JA, Kuznetsova I, Shearwood A-M, Lee RG, Matthews V, Viola HM, Johnstone VPA, Hool LC, Rackham O and Filipovska A. Adult-onset obesity is triggered by impaired mitochondrial gene expression Science Advances Aug 16;3(8):e1700677, 2017.
14. Muralidharan, P., Szappanos, H.C., Ingley, E. and Hool, L. (2016) “Evidence for redox sensing by a human cardiac calcium channel.” Nature Scientific Reports 6: 19067(1-14). First report to identify the reactive cysteine on the Cav1.2 protein and provide evidence of redox sensing by the channel clarifying controversies over whether the channel is an oxygen sensor.
15. Viola HM, Johnstone VPA, Cserne Szappanos H, Richman T, Toutsman T, Filipovska A, Semsarian C, Seidman J, Seidman C and Hool LC. The role of the L-type Ca2+ channel in altered metabolic activity in a murine model of familial hypertrophic cardiomyopathy JACC: Basic Translational Research VOL. 1, NO. 1-2, 2016
16. Richman TR, Spahr H, Ermer JA, Davies SMK, Viola HM, Bates KA, Papadimitriou J, Hool LC, Rodger J, Larsson N-G, Rackham O and Filipovska A. Loss of the RNA-binding protein TACO1 causes late-onset mitochondrial dysfunction in mice Nature Communications Jun 20;7:11884, 2016.
17. Viola HM, Johnstone VPA, Cserne Szappanos H, Richman T, Toutsman T, Filipovska A, Semsarian C and Hool LC. The L-type Ca2+ channel facilitates abnormal metabolic activity in the cTnI-G203S mouse model of hypertrophic cardiomyopathy J Physiology (London) Jul 15;594(14):4051-70, 2016. Evidence that communication between the channel and mitochondria is disrupted in TnI mutant mice and L-type Ca2+ channel current is altered.
18. Hardy N, Viola HM, Johnstone VPA, Clemons TD, Cserne Szappanos H, Singh R, Smith NM, Swaminathan Iyer K and Hool LC. Nanoparticle Mediated Dual-delivery Enables Simultaneous Action Against Myocardial Damage and Oxidative Stress in Cardiac Ischemia- Reperfusion Injury ACS Nano 9(1): 279-289, 2015. A pioneering example of dual drug delivery and parallel imaging in nanomedicine.
19. Viola HM, Adams A, Davies SKM, Fletcher S, Filipovska A and Hool LC. Impaired functional communication between the L-type calcium channel and mitochondria contributes to metabolic inhibition in the mdx heart Proceedings National Academy Sciences USA 111(28): E2905-E2914, 2014. Selected for F1000Prime recommended as being of special significance in the field. Evidence that communication between the channel and mitochondria is disrupted in mdx cardiomyopathy. Treatment with morpholino oligomers rescues metabolic inhibition.
20. Clemons TD, Viola HM, House M, Swaminathan Iyer K and Hool L. A ‘TAT-less’ delivery of a peptide against activation of the L-type calcium channels in cardiac ischemia-reperfusion injury ACS Nano 7(3): 2212-2220, 2013. First example of nanoparticle mediated delivery of peptides to the heart outperforming the traditional cell penetrating peptide performance.
21. Gaur N, Rudy Y and Hool LC. Contributions of ion-channel currents to ventricular action potential changes and induction of early afterdepolarizations during acute hypoxia. Circulation Research 105(12): 1196-203, 2009.
22. Viola HM, Arthur PG and Hool LC. Evidence for regulation of mitochondrial function by the L-type Ca2+ channel in ventricular myocytes Journal of Molecular and Cellular Cardiology 46:1016–1026, 2009. Selected for F1000Prime recommended as being of special significance in the field.
23. Hool, L.C. and Arthur, P.G. Decreasing cellular hydrogen peroxide with catalase mimics the effects of hypoxia on the sensitivity of the L-type Ca2+ channel to b-adrenergic receptor stimulation in cardiac myocytes. Circulation Research: 91:601-609, 2002.
24. Hool, L.C. Hypoxia alters the sensitivity of the L-type Ca2+ channel to a-adrenergic receptor stimulation in the presence of b-adrenergic receptor stimulation. Circulation Research 88(10): 1036-1043, 2001.
25. Hool, L.C. Hypoxia increases the sensitivity of the L-type Ca2+ channel to b-adrenergic receptor stimulation via a C2 region-containing protein kinase C isoform. Circulation Research 87(12): 1164-1171, 2000.