Cultivating ACE research skills to tackle cardiovascular disease

“The GCRF START grant has been a game-changer for young African scientists, particularly from underrepresented groups such as female, and black scientists, enabling them to enter the field of Structural Biology and thrive. This has been achieved by collaborations from Africa and the UK, outstanding workshops on research techniques, international conferences, symposia hosted in Africa, and the recruitment of African scientific officers and postdoctoral fellows.”
Prof. Edward D. Sturrock, University of Cape Town, South Africa.

GCRF START – belonging to a diverse group of African scientists

My name is Lizelle Lubbe and I am a GCRF START Postdoctoral Research Fellow. My field of research is Structural Biology, which is a scarce skill in Africa with only a handful of scientists trained in single particle cryo-EM – a cutting-edge technique for determining the structure of proteins. START provides me with the opportunity to learn from these science pioneers in Africa, as well as from experts in the UK by establishing networks for discussion and organising workshops for hands-on training. Furthermore, GCRF START provides us with the resources to conduct outreach, not only to make science accessible for the community but also to inspire the future generation of scientists. I find it very stimulating to be a part of such a diverse group of scientists who are all working together towards achieving common goals to uplift communities and find solutions to global challenges.

Dr Lizelle Lubbe, GCRF START Postdoctoral Research Fellow. Photo Credit: Rebekka Stredwick. ©Diamond Light Source

Structural Biology combines concepts of Biology, Chemistry and Physics and therefore can be quite daunting to enter. For example, the design of drugs for the treatment of disease requires one to understand how the disease develops, identify a drug target in this process, use medicinal chemistry to design a small molecule capable of blocking that target, and validate the process using structural techniques. Although this has traditionally been a more male-dominated field, the hardships endured by women in science throughout history have led to ground-breaking discoveries and a paradigm shift, so that today I have the privilege of doing my postdoctoral research using revolutionary techniques like cryo-EM.

As a result of the GCRF START grant, I am funded to do my research which includes associated travel costs for data collection, access to mentoring from experts in their field, and the use of state-of-the-art equipment and facilities such as the UK’s national synchrotron, Diamond Light Source, and the GCRF START Centre for Excellence in the University of Cape Town’s (UCT’s) Aaron Klug Centre for Imaging and Analysis. START has made it possible to gain valuable and much sought-after experience and skills in biophysical and synchrotron techniques.

From left: GCRF START collaborating scientists, Dr Priscilla Masamba, Dr Jeremy Woodward, Melissa Marx, Dr Andani Mulelu, Dr Philip Venter, Dr Lizelle Lubbe, Prof. Trevor Sewell at the University of Cape Town. Photo Credit: Rebekka Stredwick. ©Diamond Light Source

Improving the health of patients with hypertension and other diseases

My research is focused on a protein called angiotensin-converting enzyme (ACE) which is well-known for its role in blood pressure¹ regulation. It is found in many organs throughout the human body where it catalyses a reaction to produce a peptide (string of amino acids) that causes constriction of blood vessels, thereby regulating blood pressure and circulation. In some cases, however, this process goes awry, and the blood pressure becomes elevated, increasing the force of blood against the artery walls. This condition is known as hypertension and typically does not produce any noticeable symptoms.

According to the World Health Organisation, 1.13 billion people suffer from hypertension globally², with many countries in Africa³ experiencing the highest prevalence of hypertension in the world at 27% (WHO, 2019). Conditions caused by hypertension include stroke, heart failure, heart attack, kidney failure and loss of vision. There are many risk factors to hypertension, and these include family history, increasing age, stress, being overweight/obese, a diet high in salt, smoking tobacco, drinking too much alcohol, and a lack of exercise. Given the important role of ACE in blood pressure regulation, ACE inhibitors are commonly used in the clinic to effectively treat hypertension and heart/kidney disease. The use of ACE inhibitors is unfortunately linked to the development of side effects in some patients. It can be mild (loss of taste, skin rash or persistent dry cough) but also life-threatening in the case of angioedema. Angioedema is a condition where the patient develops severe swelling below the skin surface which can affect the throat, tongue and lips and obstruct the airway.

I am motivated by the potential of the research we are doing to improve the lives of patients living with hypertension and other diseases associated with ACE by increasing our understanding of the disease-causing protein. This would ultimately allow us to design ACE inhibitors with less side-effects. It is also very exciting to learn structural biology techniques such as cryo-EM and to help establish this expertise in Africa for the benefit of our community. By gaining valuable experience in the scarce field of Structural Biology, I hope to strengthen research in Africa and motivate others towards a career in science.

GCRF START Postdoctoral Research Fellow, Dr Lizelle Lubbe from the University of Cape Town (UCT) with START collaborator Dr Andani Mulelu at the University of Cape Town’s Postgraduate Showcase outreach event in July 2019. Dr Mulelu is a researcher at UCT’s Drug Discovery and Development Centre (H3D).
Photo credit: Dr Jeremy Woodward. ©Diamond Light Source

Inspired into biochemistry – persistence pays off!

The motivation I describe above started at a young age, and I was greatly inspired by my parents who both studied science – my mother studied Microbiology and my father, Mechanical Engineering. I grew up on a small farm outside Pretoria in the Gauteng province of South Africa and have been interested in the mechanism of action of therapeutic drugs from a young age. Opportunities for women in science were scarce in the early 1990’s and my mother could unfortunately no longer pursue her career after my birth. Her interest in the world of microorganisms remained, however, and inspired me to enter the field of Biochemistry where one could not only study microorganisms and other factors in relation to disease but also design therapies.

I had very limited hands-on exposure to science at the farm school I attended. My siblings and I spent many afternoons in the community library and at some point, I started reading encyclopaedias and became fascinated with science. After that, I saved some money and bought myself a second-hand toy light-microscope which occupied me for hours. However, these years were not without hardship. After obtaining his degree in Mechanical Engineering, my father single-handedly established a small business and it was very challenging to secure an income, so we were often left without certain essentials. Our school tuition was funded by government subsidies and as we could not afford private healthcare, I spent many school days in long queues since before the crack of dawn at the local District Hospital.

During my final year at high school (matric), the Physical Sciences teacher told me about the field of Biochemistry and although my parents could not afford to pay for my tertiary education, I was determined to obtain a degree and arranged to get a student loan. Persistence paid off and I obtained my undergraduate Bachelor of Science (BSc) degree at the University of Pretoria majoring in Biochemistry and Chemistry in 2011.

Great mentors – learning key Structural Biology techniques from GCRF START experts

These challenges and hardships only cemented my determination to continue in the field I am passionate about and having experienced mentors has really helped. My PhD at the University of Cape Town was supervised and co-supervised by Prof. Ed Sturrock and Prof. Trevor Sewell, respectively. They are both Co-Investigators on the GCRF START grant and, after finalising my PhD thesis, Prof. Sturrock offered me a GCRF START Postdoctoral Fellowship on a related research project in his laboratory. I started as a GCRF START postdoc in October 2018 and, in October 2019, I travelled to the UK to the Harwell Campus, and collected a dataset of ACE at the Electron Bio-Imaging Centre (eBIC) at Diamond Light Source using a Titan Krios transmission electron microscope with K3 detector. I am in the data analysis stage right now.

Dr Lizelle Lubbe transferring a puck containing the cryo-EM grids of ACE from the shipping dewar to be clipped for data collection session at eBIC at the UK’s national Diamond Light Source synchrotron. Photo credit: Dr Jeremy D Woodward. ©Diamond Light Source

GCRF START Postdoctoral Research Fellow,Dr Lizelle Lubbe, with START collaborator, Melissa Marx from the University of Cape Town (UCT) next to the Titan Krios III (M06) at eBIC embedded at the UK’s national Diamond Light Source synchrotron, which was used to image ACE. Melissa is an MSc student co-supervised by Dr Woodward at UCT.
Photo credit: Dr Jeremy Woodward. ©Diamond Light Source

Professor Sturrock⁴ is a leader in the design of anti-hypertensive drugs and was an excellent mentor during my BSc (Med)(Hons) in Medical Biochemistry (completed in 2012) and PhD in Chemical Biology (completed in 2018) studies. He has taught me how to think critically about the problem at hand and to persevere despite the numerous setbacks one experiences as a scientist. For example, Structural Biology techniques such as X-ray crystallography, molecular dynamics (MD) simulations and cryo-electron microscopy (cryo-EM) are key to understanding proteins involved in disease and how to target them.

However, because advanced Mathematics or Physics modules were not included in my undergraduate training, it was really difficult for me to learn the theoretical aspects of these techniques and how it is applied in practice. I am therefore very grateful for the START project which has given me the opportunity to learn from experts in the field of Structural Biology – experts such as Dr Jeremy Woodward and Prof.Trevor Sewell from the UCT Aaron Klug Centre for Imaging and Analysis. A further challenge throughout my PhD was my limited background in Computational Science. The computer skills I learned from high school were very elementary which meant a particularly steep learning curve when I decided to use MD simulations to answer key research questions.

GCRF START Co-Investigator, Prof. Ed Sturrock, and GCRF START Postdoctoral Fellow, Dr Lizelle Lubbe, at the GCRF START launch in Oxford, UK.
Photo credit: Prof. Ed Sturrock. ©Diamond Light Source

Studying ACE for the future design of ACE inhibitors

ACE is a dumbbell-shaped protein comprised of two domains (the N- and C-domain) which perform diverse physiological functions: the C-domain is mainly responsible for blood pressure regulation while the N-domain is important for regulating scar tissue formation. The main focus of Prof. Sturrock’s research is to design inhibitors that selectively bind to the N- or C-domain. Selectivity is very important since the side-effects associated with current ACE inhibitors are due to equal inhibition of both domains. At the end of my BSc (Med)(Hons) year, Prof. Sturrock (in collaboration with Prof. Kelly Chibale at UCT) discovered a molecule (33RE) which binds with 1000-times greater affinity to the N-domain than the C-domain of ACE^5. N-selective ACE inhibitors are antifibrotic and as such, show potential for the treatment of fibrosis (excessive scar tissue formation). X-ray crystallography was used to study the binding of 33RE to the N-domain but the reason for its selectivity remained a mystery. One limitation of this technique is that it only gives you a static ‘snapshot’ of the protein’s structure while proteins are naturally very dynamic when in solution (as in the body).

For my PhD research, I therefore decided to study ACE using MD simulations. In this technique, the atoms in the crystal structure are allowed to move which can provide more insight into how the drug interacts with the protein. My results were really interesting and showed that subtle amino acid differences between the two domains caused drastic changes in their dynamics and thereby, their affinity for 33RE⁶.

GCRF START ensures the continuation of postdoctoral research

As a GCRF START postdoc, I am continuing this research in collaboration with Prof. K Ravi Acharya⁷ at the University of Bath and we have recently discovered that these differences in dynamics also affect the binding and selectivity of ACE inhibitors from different classes⁸⁹. This has great implications for the future design of ACE inhibitors and emphasizes the importance of using a range of biophysical techniques when studying proteins. The workshops funded by the GCRF START grant has equipped me with valuable skills and I am very excited to discover even more insight into the workings of ACE by applying these skills.

The biggest challenge on my road to becoming a scientist has been financing ten years of tertiary study. Although I was fortunate enough to receive merit and government bursaries to fund my PhD, I am still paying off the student loan from my undergraduate and honours years. Therefore, funding through the GCRF START grant has been invaluable, ensuring the continuation of my postdoctoral research.

Commenting on Lizelle’s achievements and the impact of the GCRF START grant on emerging African scientists like Lizelle, Prof. Ed Sturrock said,

“The GCRF START grant has had a significant impact on Lizelle’s career development, career opportunities and personal growth. Her progress with a very challenging research project and her involvement in other GCRF START activities, such as the START outreach project to uplift the community and promote science through art, bear testament to this. I have been enormously impressed by what Lizelle has achieved as a START postdoctoral research fellow in a relatively short period of time.”

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