Role of N- and C-terminal fibrinogen beta-chain residues in fibrin catch-slip bond behaviour: relevance to clot properties and thromboembolism

A fully funded 3-year PhD studentship, sponsored by the British Heart Foundation, is available in the School of Medicine, starting in October 2024. This project will be led by Dr. Cédric Duval and Prof. Robert Ariëns from the Leeds Institute of Cardiovascular and Metabolic Medicine.

This project focuses on characterising a unique type of bond crucial in protein interactions: the catch-slip bond. Protein interactions involve various non-covalent bonds such as ionic forces, van der Waals interactions, and hydrogen bonding. Recent studies have identified two main types of bonds: ‘slip’ bonds weaken as proteins are pulled apart, and ‘catch-slip’ bonds initially strengthen (‘catch’ phase) before slipping at higher force. More protein interactions, including the fibrin-fibrin interaction essential in blood clotting, are recognised as ‘catch-slip’ bonds.

Abnormal blood clotting is crucial in thrombotic diseases like heart attack, stroke, and venous thromboembolism. Fibrinogen converts to fibrin after cleavage by thrombin, forming a three-dimensional clot backbone. Thrombin cleavage exposes N-terminal knobs ‘A’ and ‘B’, binding tightly to holes ‘a’ and ‘b’. The resulting A:a and B:b interactions, crucial for protofibril formation and fibrin fibre network branching, exhibit catch-slip bond behaviour [1,2]. Beyond the knob and hole sites, additional interactions likely contribute to this behaviour, enhancing binding during fibrin polymerisation. 

We recently showed that mutations in the C-terminal domain of the γ-chain reduce the ‘catch’ and increase the ‘slip’ behaviour of the A:a bond [3]. These mutations significantly alter clot structure and biomechanical properties [3]. N-terminal residues of the beta-chain may also influence the A:a interaction, while C-terminal residues of the beta-chain contribute to the catch-slip behaviour of the B:b interaction, as observed in computational models [2]. However, the precise role of beta-chain residues in fibrin polymerisation requires further investigation.

In this project, you will explore the significance of extended regions of the fibrin beta-chain in A:a and B:b interactions during the polymerisation process, aiming to uncover potential strategies for inhibiting thrombosis. The project objectives include: 

• Investigating the individual contributions of A:a and B:b interactions to fibrin polymerisation.
• Assessing the impact of specific residues involved in A:a and B:b interactions on clot formation, lysis, and biomechanical properties in-vitro.
• Utilising computational modelling to simulate the effects of these specific residues on catch-slip knob-hole interactions in-silico.
• Validating the observed catch-slip bond behaviour ex-vivo.

Here, you will develop a comprehensive skill set crucial for future research. This includes expertise in protein mutagenesis, expression, and purification. You will also gain proficiency in analysing clot formation and structure using techniques such as turbidity measurement, laser-scanning confocal microscopy, scanning electron microscopy, and atomic force microscopy. Additionally, you will explore clot viscoelastic properties using specialised methods, like magnetic tweezers and lateral force microscopy, unique to our lab. Furthermore, you will expand your experience through a visit to Prof. Valeri Barsegov’s laboratory at the University of Massachusetts – Lowell. During this collaboration, you will engage in molecular dynamic simulations focusing on fibrin polymerisation, particularly studying key fibrinogen mutants identified in your research.

Eligibility

This studentship is only available to applicants who are eligible to pay academic fees at the UK Home rate.

You should hold at least a 2:1 UK Honours degree (or international equivalent), or a MSc degree, in a relevant subject.

If English is not your first language, you must provide evidence that you meet the University’s minimum English language requirements. The minimum English language entry requirement for postgraduate research study in the School of Medicine is an IELTS of 6.5 overall with at least 6.0 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid.

How to Apply

To apply for this scholarship opportunity, applicants should complete an online application form and attach the following documentation to support your application. 

• A full academic CV
• Degree certificate and transcripts of marks (or marks so far if still studying)
• Evidence that you meet the programme’s minimum English language requirements (if applicable)

To help us identify that you are applying for this scholarship project please ensure you provide the following information on your application form;

• Select PhD in Medicine as your planned programme of study
• Give the full project title and name the supervisors listed in this advert
• For source of funding please state that you are applying for a BHF PhD Studentship

To apply for this scholarship opportunity, applicants should complete an online application form and attach the following documentation to support your application. 

• A full academic CV
• Degree certificate and transcripts of marks (or marks so far if still studying)
• Evidence that you meet the programme’s minimum English language requirements (if applicable)

To help us identify that you are applying for this scholarship project please ensure you provide the following information on your application form;

• Select PhD in Medicine as your planned programme of study
• Give the full project title and name the supervisors listed in this advert
• For source of funding please state that you are applying for a BHF PhD Studentship

For information about the project please see the University website or contact C.Duval@leeds.ac.uk (please state “BHF studentship” in the subject line). Informal enquiries are encouraged.

For further information about the admissions process please contact the FMH PGR Admissions Team: fmhpgradmissions@leeds.ac.uk