Dr Isabel Llorente-Garcia
No more applications being accepted
Funded PhD Project (European/UK Students Only)
The cell membrane is the main barrier that viruses need to overcome to penetrate cells and cause disease. As part of their entry strategy, viruses interact with specific receptor proteins at the cell surface in ways which are not well understood. These cell-surface receptors are typically embedded in the membrane of the cell, where they can diffuse in the membrane plane, as well as interact with the cellular cytoskeleton (a mesh of filaments beneath the cell membrane). The physical properties of virus receptors, such as their mobility and interactions with the cytoskeleton, are likely to have an important role in virus entry and are not well known.
We will focus on the Human Immunodeficiency Virus (HIV), known to interact with specific receptor molecules on the surface of cells of the immune system. These receptors are the CD4 receptor and CCR5/CXCR4 chemokine receptors. An HIV particle first binds these receptors. Following this initial binding, receptors are known to redistribute on the cell surface, clustering towards the site of virus binding. Eventually, the virus penetrates the cell membrane and releases its genome into the cellular cytoplasm, initiating infection.
This PhD project aims at measuring CD4 mobility and understanding CD4 clustering in HIV entry via the following milestones: (i) Measuring the single-molecule, long-range mobility of CD4 molecules on the surface of living cells, in the absence of virus, for full-length and cytoplasmic-domain-deleted CD4 variants, as well as using drugs that disrupt membrane-cytoskeleton attachments. These measurements will determine the effect of receptor-cytoskeleton interactions in the mobility required for receptor redistribution and recruitment to virus-binding sites; (ii) Measuring the long-range mobility and clustering of CD4 receptors upon virus binding. These measurements will reveal what changes in CD4 mobility or receptor-cytoskeleton interactions might enable or inhibit receptor clustering in HIV entry; (iii) Measuring mobility in living T cells, as a dynamic visualisation of CD4 recruitment in HIV entry in physiological cell targets; (iv) Developing a new model of receptor clustering in the membrane of living cells including receptor diffusion, receptor-cytoskeleton anchoring and hop diffusion across cytoskeletal barriers in the presence of thermal fluctuations, and comparing to experimental results.
Measurements will be taken using our bespoke fluorescence-force microscopy platform, which combines fluorescence microscopy and optical tweezers. Receptor mobility will be measured by fluorescently labelling CD4 molecules in living cells and applying single-molecule light-sheet fluorescence microscopy and single particle tracking analysis (Matlab). There will also be an opportunity for measuring forces with optical tweezers if required. You will have the opportunity to learn cell culture, fluorescence labelling of cell-surface receptors, various biochemical and cell and molecular biology techniques, programming for controlling equipment, various data analysis approaches including image processing, and modelling techniques.
You will work in a multi-disciplinary environment under the supervision of Dr Isabel Llorente-García, in the AMOPP and Biological Physics Groups within the Dept. of Physics and Astronomy at University College London, UK. Additionally, you will closely collaborate with Prof Mark Marsh (MRC Laboratory for Molecular Cell Biology – LMCB) with access to LMCB facilities for the biology work, and with Prof Ian Ford (UCL Physics) for the modelling work. We are part of the Institute for the Physics of Living Systems (IPLS), a lively cross-faculty institute with a mission to promote interdisciplinary research for a fundamental understanding of the complex behaviours of living systems.
ELIGIBILITY: UK/EU citizens. You should have a high grade point average MSci or Master’s degree (or equivalent) in Physics, Engineering or similar. No prior knowledge of Biology is necessary. Previous experience in experimental research, lasers and optics, Matlab programming and/or modelling is highly desirable, along with an interest in biological physics. A high level of self-motivation and enthusiasm is essential, as well as good communication skills and excellent writing skills.
How to apply: Please send applications by email to [Email Address Removed] including:
• a CV (2 page max.),
• a full transcript of records with course grades to date,
• contact details for two academic or professional referees (at least one academic),
• a personal statement (700 words maximum) outlining your academic excellence, research experience to-date and suitability for the project.
Interviews will be held in February-March 2020. Only shortlisted candidates will be notified via email.
Funding: The stipend is approx. £17,400 per annum (2020/21 rate) and tuition fees are covered. The funding duration is 3.5 years. The starting date is approx. October 2020.
Suggested reading: A biophysical perspective on receptor-mediated virus entry with a focus on HIV, I. Llorente Garcia and M. Marsh, BBA: Biomembranes (2019), https://doi.org/10.1016/j.bbamem.2019.183158
Research group website: https://illglab.wordpress.com/