LICAMM Role of N- and C-terminal fibrinogen Beta-chain residues in fibrin catch-slip bond behaviour

Role of N- and C-terminal fibrinogen β-chain residues in fibrin catch-slip bond behaviour: relevance for clot mechanical properties and thromboembolism<br /> <br /> 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.

<p>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.</p> <p>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 β-chain may also influence the A:a interaction, while C-terminal residues of the β-chain contribute to the catch-slip behaviour of the B:b interaction, as observed in computational models [2]. However, the precise role of β-chain residues in fibrin polymerisation requires further investigation.</p> <p>In this project, you will explore the significance of extended regions of the fibrin β-chain in A:a and B:b interactions during the polymerisation process, aiming to uncover potential strategies for inhibiting thrombosis. The project objectives include:</p> <ul> <li>Investigating the individual contributions of A:a and B:b interactions to fibrin polymerisation.</li> <li>Assessing the impact of specific residues involved in A:a and B:b interactions on clot formation, lysis, and biomechanical properties in-vitro.</li> <li>Utilising computational modelling to simulate the effects of these specific residues on catch-slip knob-hole interactions in-silico.</li> <li>Validating the observed catch-slip bond behaviour ex-vivo.</li> </ul> <p>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.</p> <h5>References:</h5> <ol> <li>Litvinov RI, Kononova O, Zhmurov A, et al. Regulatory element in fibrin triggers tension-activated transition from catch to slip bonds. Proc Natl Acad Sci USA. 2018; 115(34): 8575-8580.</li> <li>Kononova O, Litvinov RI, Zhmurov A, et al. Molecular mechanisms, thermodynamics, and dissociation kinetics of knob-hole interactions in fibrin. J Biol Chem. 2013; 288(31): 22681-22692.</li> <li>Asquith NL, Duval C, Zhmurov A, et al. Fibrin protofibril packing and clot stability are enhanced by extended knob-hole interactions and catch-slip bonds. Blood Adv. 2022; 6(13): 4015-4027.<br />  </li> </ol>

<p>Please note these are not standalone projects and applicants must apply to the PhD academy directly.</p> <p>Applications can be made at any time. You should complete an <a href="https://medicinehealth.leeds.ac.uk/faculty-graduate-school/doc/apply-2">online application form</a> and attach the following documentation to support your application. </p> <ul> <li>a full academic CV</li> <li>degree certificate and transcripts of marks (or marks so far if still studying)</li> <li>Evidence that you meet the programme’s minimum English language requirements (if applicable, see requirement below)</li> <li>Evidence of funding to support your studies</li> </ul> <p>To help us identify that you are applying for this project please ensure you provide the following information on your application form;</p> <ul> <li>Select PhD in Medicine, Health & Human Disease as your planned programme of study</li> <li>Give the full project title and name the supervisors listed in this advert</li> </ul>

A degree in biological sciences, dentistry, medicine, midwifery, nursing, psychology or a good honours degree in a subject relevant to the research topic. A Masters degree in a relevant subject is desirable, but not essential.

Applicants whose first language is not English must provide evidence that their English language is sufficient to meet the specific demands of their study. The minimum requirements for this programme in IELTS and TOEFL tests are: • British Council IELTS - score of 7.0 overall, with no element less than 6.5

<p>For further information please contact the Faculty Admissions Team:<br /> e:<a href="mailto:fmhpgradmissions@leeds.ac.uk">fmhpgradmissions@leeds.ac.uk</a></p>