University of Cambridge
Molecular insights into signalling mechanisms within TGF-β superfamily
Abstract
dc:description.abstractThe TGF-β superfamily includes receptors, extracellular signalling molecules, their inhibitors and intracellular downstream signalling components. Members of the superfamily are present in all metazoans, expressed in all cells of the body and they are involved in embryonic development, adult tissue homeostatis and reproduction. A great deal is known about the structural biology of the TGF-β superfamily, however the absence of the full-length receptor-ligand complex structure is hindering our understanding of the conformational changes that are driving the TGF-β superfamily receptor signalling mechanism. Similarly, because of the absence of the solution structure of follistatin (an extracellular inhibitor of several TGF-β superfamily signalling molecules) it is unclear how its C-terminal tail affects its function. In this work I employed a combination of small-angle X-ray scattering (SAXS) and biophysical assays to model the full-length structure of follistatin to understand its behaviour in solution. I also used cell transfection experiments and signalling assays conducted within the bacterial membrane to both purify full-length TGF-β superfamily receptor-ligand complex and to understand the importance of transmembrane helices in TGF-β superfamily receptor signalling, respectively. The results presented here demonstrate that the C-terminus of follistatin stretches back along the surface of the molecule and interacts with its FS1 domain hindering follistain’s ability to bind to heparan sulphate and to inhibit TGF-β superfamily signalling molecules. Additionally, SAXS-based modelling of follistatin’s solution structure demonstrates that all three full-length follistatin isoforms alternate between two different solution conformations. On the TGF-β superfamily receptor side, I demonstrated that the transmembrane helices of ALK2 and ALK4 receptors homodimerize and designed a novel bacterial signalling assay that can test for transmembrane helix heterodimerisation that overcomes problems with existing similar assays. Overall, I have demonstrated that structural components of the TGF-β superfamily that were overlooked during previous studies have a significant impact on the structure of its receptors and inhibitors and have provided molecular insights into their biological function.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2023
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Stepurko, Natalija
- Advisor dc:contributor.advisor
-
- Broadhurst, Richard
Subjects
dc:subject × 5Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.99087
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/352937