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The Stewart lab has an opening for a Research Assistant in Biochemical Ophthalomology for a period of 24 months. For details of the post and how to apply see the link.

Cardiac excitation-contraction (EC) coupling, a process which governs contractility of the heart, depends on the controlled release of calcium ions (Ca²⁺) from the sarcoplasmic reticulum (SR) through specialised Ca²⁺-release channels called type-2 ryanodine receptors (RyR2). RyR2 plays a pivotal role as the main pathway for the release of Ca²⁺, driving cellular contraction. Consequently, dysfunction in the release of Ca²⁺ through these channels and the modulatory influences which control RyR2 function have been identified as contributory to the pathophysiology of heart failure and fatal cardiac arrhythmias.

Very recently a link between elevated levels of intracellular zinc and heart disease has been highlighted, but very little is understood regarding the role of zinc in the heart. In this latest publication in The Journal of Biological Chemistry the Pitt group show that Zn²⁺ is a high affinity regulator of RyR2 displaying three modes of operation. Picomolar free Zn²⁺ concentrations potentiate RyR2 responses but channel activation is still dependent on the presence of cytosolic Ca²⁺. At concentrations of free Zn²⁺ >1 nM, Zn²⁺ is the main activating ligand and the dependency on Ca²⁺ is removed. Zn²⁺ is therefore a higher affinity activator of RyR2 than Ca²⁺. This work suggest that RyR2-mediated Ca²⁺-homeostasis is intimately related to intracellular Zn²⁺ levels providing a mechanistic explanation linking altered Zn²⁺ homeostasis to cardiac RyR2 function.The data presented represents a shift in our understanding of how RyR2 is activated during EC coupling and indicates that channel dysregulation, through aberrant Zn²⁺ homeostasis, is likely to play a fundamental role in the generation of heart failure and other arrhythmic diseases. Full text is available online.

A research grant of £110,951 has been awarded to Dr Alan Stewart and Dr Imre Lengyel (UCL Institute of Ophthalmology) from Fight for Sight to carry out a new 2-year study entitled “Identifying the hydroxyapatite interactome: clarifying the involvement of serum proteins in the formation of sub-retinal pigment epithelial (RPE) deposits”. A major feature of the ageing retina is the thickening of Bruch’s membrane and the formation of sub-retinal pigment epithelial (RPE) deposits that can block metabolic exchange between the choroidal blood circulation and the retina leading to sensory retinal degeneration and eventually to age-related macular degeneration (AMD), a major cause of visual impairment and blindess in older adults (>50 years). Recently, Thompson et al. reported the existence of small (0.5-20 μm diameter) protein-binding hydroxyapatite (HAP) spherules within sub-RPE deposits isolated from AMD-affected individuals (see link). This suggests that the spherules may provide nucleation sites for sub-RPE deposit formation, where the initiation, growth and retention of deposits are controlled by the binding of proteins present in the sub-RPE space to the spherules. In the funded study, HAP-binding proteins in the plasma of genotyped late-stage AMD patients will be isolated and quantitatively identified and biochemically characterised.

The Physiological Society, Techniques Workshop – An Introduction to Molecular Biology, UCL, 14-17 april 2015.

Ben and Gavin found the course very informative and enjoyable. The techniques learned have already been used in the lab!

Ben and Gavin would like to thank, the Physiological Society and the course organisers specifically Caroline Pellet-Many who coordinated the whole week.

A research grant of £191,250 has been awarded to Dr Alan Stewart from the British Heart Foundation to carry out a new 3-year study entitled “Role of zinc in controlling histidine-rich glycoprotein (HRG) complex formation: Implications for the development of thrombotic complications”. This work will advance current knowledge of the structure and function of HRG, a key molecule involved in controlling coagulation, and its regulation of haemostasis in health and disease. In addition, the project will evaluate a potentially novel zinc-dependent haemopathological mechanism in diabetes patients stemming from elevated plasma FFA levels and modulation of HRG functioning. The study is a collaboration between investigators at the University of St Andrews (Dr Stewart, Dr Samantha Pitt and Prof. James Naismith) and the University of Leeds (Dr Ramzi Ajjan).

The Northwood Charitable Trust has just awarded Dr Samantha J. Pitt a small grant (£21,000) titled “Regulation of cardiac function; new mechanisms and novel ion channels”

This research will address the role of zinc signalling in regulating sarcoplasmic reticulum ion-channel function during excitation contraction coupling, and will characterise the potential detrimental role of zinc in cardiomyopathies.

Many thanks for supporting our research.

Was great meeting all of the S4 pupils from St Andrews High, Kirkcaldy, at the routes into employment STEM “speed dating” event yesterday. I hope they enjoyed it as much as I did. I wish them all the best in their future careers. – Dr Samantha J. Pitt

Dr Samantha Pitt and Dr Alan Stewart would like to thank the British Heart Foundation for supporting their research titled “Understanding new mechanisms of cardiac ryanodine receptor regulation by zinc”. These funds will support Gavin Robertson during his PhD research.

Gavin starts his PhD today!

Histidine-rich glycoprotein (HRG) is a plasma protein that regulates a number of biological processes in the blood including coagulation, through its ability to bind and neutralize heparins. HRG contains a distinctive histidine-rich region that associates with zinc ions (Zn²⁺) to stimulate HRG-heparin complex formation. Under normal conditions the majority of Zn²⁺ in plasma associates with serum albumin. However, clinically high levels of free fatty acid (FFA) allosterically disrupt the major Zn²⁺-binding site on serum albumin and are associated with an increased risk of thrombotic complications. The Stewart group report in the Journal of Thrombosis and Haemostasis that increased levels of circulatory fatty acids are likely to increase the proportion of plasma Zn²⁺ associated with HRG. In this study the Zn²⁺-binding properties of HRG and the formation of HRG-heparin complexes in the presence of different Zn²⁺ concentrations were investigated. Furthermore, the binding of Zn²⁺ to serum albumin was examined in the presence of various concentrations of myristate by ITC. Speciation modeling of plasma Zn²⁺ based upon the data obtained from these experiments suggests that FFA-mediated displacement of Zn²⁺ from serum albumin is likely to contribute to the development of thrombotic complications in individuals with high plasma FFA levels – Full text is available online.