Probing the conformational dynamics and oligomerisation of human islet amyloid polypeptide using state-the-art tandem ion mobility mass spectrometry.

Professor Konstantinos Thalassinos (UCL) and Dr. Johannes P.C. Vissers (Micromass UK Ltd)

We will study the conformational dynamics and early oligomerisation processes of wild type and variant human islet amyloid polypeptide (hIAPP), also known as amylin. hIAPP is a 37-residue pancreatic hormone responsible for β-cell death in the pancreas which plays a critical role in type-2 diabetes (T2D). We will examine in detail the effect hIAPP sequence variants have on protein conformation, oligomerisation, and cell toxicity. In addition to using more established biochemical, biophysical and cell-based characterisation approaches, we will study such processes using a novel cyclic ion mobility mass spectrometer (cIMMS) equipped with electron capture dissociation (ECD) capabilities.

Under normal physiological conditions, hIAPP plays an adaptive role in metabolic regulation but converts via an unknown cytotoxic mechanism into insoluble extracellular pancreatic amyloid fibrils in diabetes. It is now widely accepted that early oligomeric states are key to protein self-assembly and subsequent amyloid disease. The assembly mechanism and the structure of the toxic soluble oligomers, however, remains poorly understood, largely due to the inability of conventional techniques to probe either distributions or detailed structures of early oligomeric species which are heterogeneous and difficult to trap.

cIMMS, is an excellent method for studying in detail heterogeneous samples and for isolating conformers for further study. Due to its unique design, the cIMMS can isolate closely related conformers for further higher resolution (tandem ion mobility) conformational analysis. The addition of ECD, a gas-phase fragmentation technique that fragments covalent bonds while preserving noncovalent interactions, will provide further structural information.  Mobility isolated conformers will be subjected to ECD to reveal regions of interactions. The combination of tandem ion mobility and ECD is currently not possible with any other commercial IMMS instrumentation.

We anticipate any findings, and methods developed, to be applicable to other conformational diseases whose incidence increases in ageing populations due to breakdown of protein homeostasis and which have so far been intractable to study by other established techniques.

The student will be working in a highly multidisciplinary environment and acquire skills in diverse fields (biology, cutting-edge analytical chemistry, data analysis and software development) but also be exposed to working life in a commercial setting. It will equip them with many skills which are currently in very high demand.

References:

1. Britt, H. M., T. Cragnolini and K. Thalassinos (2022). "Integration of Mass Spectrometry Data for Structural Biology." Chem Rev 122(8): 7952-7986.
2. Eldrid, C., A. Ben-Younis, J. Ujma, H. Britt, T. Cragnolini, S. Kalfas, D. Cooper-Shepherd, N. Tomczyk, K. Giles, M. Morris, R. Akter, D. Raleigh and K. Thalassinos (2021). "Cyclic Ion Mobility-Collision Activation Experiments Elucidate Protein Behavior in the Gas Phase." J Am Soc Mass Spectrom 32(6): 1545-1552.
3. Ridgway, Z., K. H. Lee, A. Zhyvoloup, A. Wong, C. Eldrid, E. Hannaberry, K. Thalassinos, A. Abedini and D. P. Raleigh (2020). "Analysis of Baboon IAPP Provides Insight into Amyloidogenicity and Cytotoxicity of Human IAPP." Biophysical Journal 118(5): 1142-1151.
4. Ridgway, Z., C. Eldrid, A. Zhyvoloup, A. Ben-Younis, D. Noh, K. Thalassinos and D. P. Raleigh (2020). "Analysis of Proline Substitutions Reveals the Plasticity and Sequence Sensitivity of Human IAPP Amyloidogenicity and Toxicity." Biochemistry 59(6): 742-754.