program
14:30 - "The cryo-EM structure of human thyroglobulin"
Francesca Coscia, MRC Laboratory of molecular biology, Cambridge, UK
Thyroglobulin (TG) is the protein precursor of thyroid hormones, which are essential for growth, development and the control of metabolism in vertebrates[1]. Hormone synthesis from TG occurs in the thyroid gland via the iodination and coupling of pairs of tyrosines, and is completed by TG proteolysis. Tyrosine proximity within TG is thought to enable the coupling reaction but hormonogenic tyrosines have not been clearly identified, and the lack of a three-dimensional structure of TG has prevented mechanistic understanding[2]. Here we present the structure of full-length human thyroglobulin at a resolution of approximately 3.5 Å, determined by cryo-electron microscopy. The structure was verified by use of mass spectrometry cross-linking giving an excellent agreement with the long range interactions seen in the cryoEM model. We identified all of the hormonogenic tyrosine pairs in the structure, and verified them using site-directed mutagenesis and in vitro hormone-production assays using human TG expressed in HEK293T cells. Our analysis revealed that the proximity, flexibility and solvent exposure of the tyrosines are the key characteristics of hormonogenic sites. We transferred the reaction sites from TG to an engineered tyrosine donor–acceptor pair in the unrelated bacterial maltose-binding protein (MBP), which yielded hormone production with an efficiency comparable to that of TG. Our study provides a framework to further understand the production and regulation of thyroid hormones and paves the way for better understanding of thyroid cancer, auto-immune diseases and brain growth in foetal development[3,4].
References:
[1] Holzer, G. et al. Thyroglobulin represents a novel molecular architecture of vertebrates. J. Biol. Chem. 291, 16553–16566 (2016)
[2] Citterio, C. E., Targovnik, H. M. & Arvan, P. The role of thyroglobulin in thyroid hormonogenesis. Nat. Rev. Endocrinol. 15, 323–338 (2019)
[3]Di Jeso, B. & Arvan, P. Thyroglobulin from molecular and cellular biology to clinical endocrinology. Endocr. Rev. 37, 2–36 (2016)
[4]Fiore, E., Latrofa, F. & Vitti, P. Iodine, thyroid autoimmunity and cancer. Eur. Thyroid J. 4, 26–35 (2015)
15:30 - "Self-Assembly: from models to gluten-related disorders"
Veronica Dodero, Bielefeld University, Germany
Self-assembly drives towards systems of increasing complexity under the pressure of molecular information. The main characteristic of biological self-assembly is the variety and complexity of the functions that it produces, which can be a trigger and modify depending on external or internal stimuli. In this context, protein aggregation belongs to biological self-assembly where proteins or their fragments organize themselves alone or with other cellular components into high order structures like oligomers and fibrils triggering different human diseases. In this sense, our research is directed towards the understanding of peptide/protein self-assembly by using model systems. By this approach, we recently postulated a new pathological scenario in the context of gluten-related disorders.
Gluten is a protein complex present mainly in wheat but also in barley, rye and some oats. These proteins are not fully digested for any human triggering different immune responses in susceptible individual leading: gluten allergy (0.1%), celiac disease, CD, (1%) and more recently to non-celiac gluten sensitivity with a higher prevalence worldwide (7%). Gliadin, one of the immunogenic proteins present in wheat, is not fully degraded by humans. After the normal gastric and pancreatic digestion, the immunodominant 33-mer gliadin peptide remains unprocessed and transported through the entire human body [1]. Although the primary structure of 33-mer has a protagonist role in disease, many controversies remain at the molecular and cellular level. We demonstrated that the 33-mer forms oligomers in vitro showing a structural transition towards a beta-parallel structure and formation of protofilaments. Considering the relevance of protein nanostructures in other human diseases, we hypothesized that oligomerization of 33-mer can be the early common event that triggers gluten-related disorders [2, 3]. Recently, we showed that 33-mer supramolecular structures activate Toll-Like Receptors which are essential receptors in the activation of the primordial innate immune response [4]. Our current efforts are directed to understand the molecular and structural features of 33-mer oligomerization and the visualization of the 33-mer nanostructures in cell models [5]. Our latest findings will be presented providing new evidence about the role of gliadin peptides aggregates as triggers of gluten-related disorders.
References:
[1] L. M. Lammers et al. “Translational Chemistry meets gluten-related disorders“, ChemistryOpen 7 (2018) 217.
[2] M. G. Herrera et al. “Self-assembly of 33-mer gliadin peptide oligomers,” Soft Matter 11 (2015) 11, 8648.
[3] M. G. Herrera et al. “Circular Dichroism and Electron Microscopy Studies in vitro of 33-mer Gliadin Peptide revealed Secondary Structure Transition and Supramolecular Organization, “ Biopolymers 101 (2014) 96.
[4] M. G. Herrera et al. “Large Supramolecular Structures of 33-mer Gliadin Peptide Activate Toll-like Receptors in Macrophages“, Nanomedicine: NBM 14 (2018) 1417.
[5] M. J. Amundarain et al. “Molecular Mechanisms of 33-mer Gliadin Peptide Oligomerisation“ Phys. Chem. Chem. Phys. 21 (2019) 22539.
Host: Rita Grandori, Francesco Peri