Discovering the neuronal signalling mechanism at the heart of cardiac arrhythmias
Background: Cardiac arrhythmias are a leading cause of mortality and long-term morbidity worldwide. Over 25% of these originate in the heart’s electrically-autonomous (pacemaking) cells without a detectable heart attack. Inappropriate release of calcium from internal compartments (e.g. endoplasmic reticulum) into the cytoplasm of pacemaker cells is central to this pathology. Recent reports suggest that a small group of intracellular calcium channels, ryanodine receptor type-3 (RyR3) – historically associated with neuronal signalling – can interact with other calcium handling proteins to trigger arrhythmogenic calcium signals. The molecular mechanism and locations of RyR3 and its partners seeding these arrhythmias are unknown.
Objectives: (i) To locate RyR3 and its partner proteins which trigger arrhythmogenic calcium signals in pacemaker cells at nanometre precision (ii) To use pharmacological inhibitors tested previously on neuronal cells for perturbing the calcium signals inappropriately triggered by RyR3.
Timeliness: A number of current anti-arrhythmic therapies target other calcium handling proteins and involve significant risks. Identification of RyR3 and partners as a trigger mechanism for arrhythmias in pacemaker cells would be crucial to developing alternative and potentially safer therapies.
Novelty: RyR3, until now, has not been linked with heart disease. This project will utilise the latest super-resolution microscopy tools like Expansion Microscopy and DNA-PAINT to pinpoint the epicentres of arrhythmogenic calcium signals at an unprecedented spatial resolution.
Approach: You will exploit the leading-edge super-resolution microscopy tools (DNA-PAINT and Expansion Microscopy) pioneered by the Nanoscale Microscopy Group in Leeds (website: https://musclesuperres.com/ ), to visually examine how RyR3s are organised in the pacemaking (sinoatrial node) cells of healthy hearts. You will then examine a rat model prone to arrhythmias, comparing how RyR3, IP3-receptors and SERCA proteins are re-arranged in the nanometre-scale during the pathology. You will complete at least two secondments with the industrial partner Badrilla Ltd (website: https://badrilla.com/) to design, manufacture and test bespoke antibody labels which will allow you to map the arrhythmogenic calcium signals against the underpinning RyR3 and partner protein layouts. For this, you will harness a novel correlative microscopy protocol developed by the primary supervisor for overlaying calcium and DNA-PAINT images. Using pharmacological inhibitors of IP3R and SERCA established for studying dorsal root ganglion neurons, you will modulate the calcium handling of RyR3 and partners to understand how the signals can be reverted towards a healthy phenotype.
Key outcomes will include mechanistic schemes of the molecular-scale factors in RyR3-mediated calcium signals seeding arrhythmias and a set of pharmacological strategies to impede them.
Research environment: You will be embedded in the Nanoscale Microscopy Group, nested within the Cardiovascular Research group in the University of Leeds (working with Dr Izzy Jayasinghe and Prof Ed White). This is one of the UK’s leading clusters of researchers examining the cellular mechanisms of cardiovascular diseases. You will form bridges between this group, Prof Nikita Gamper of the Leeds Neuroscience group, Badrilla Ltd which is one of the leading specialists of analytical reagents for the cardiovascular sciences, and our international collaborators in Australia, New Zealand and USA.
Benefits of being in the DiMeN DTP: This project is part of the Discovery Medicine North Doctoral Training Partnership (DiMeN DTP), a diverse community of PhD students across the North of England researching the major health problems facing the world today. Our partner institutions (Universities of Leeds, Liverpool, Newcastle and Sheffield) are internationally recognised as centres of research excellence and can offer you access to state-of the-art facilities to deliver high impact research. We are very proud of our student-centred ethos and committed to supporting you throughout your PhD. As part of the DTP, we offer bespoke training in key skills sought after in early career researchers, as well as opportunities to broaden your career horizons in a range of non-academic sectors.
1. Jayasinghe, I. et al. True molecular scale visualisation of variable clustering properties of ryanodine receptors. Cell Reports. 2018; 22 (2), 557-567
2. Ouyang, K. et al. Ca2+ sparks and secretion in dorsal root ganglion neurons. PNAS. 2005; 102 (34) 12259-12264
3. Jayasinghe, I. et al. Shining new light on the structural determinants of cardiac couplon function. Frontiers in Physiology. doi: 10.3389/fphys.2018.01472