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Structural and functional investigation of the C-terminal intrinsically disordered fragment of ErbB2

Abstract : ErbB2/HER2 is a receptor tyrosine kinase of the EGFR (ErbB1) family overexpressed in 20% of breast cancers and associated to a particularly aggressive form of the disease. ErbB receptors are only active upon dimerization that enables phosphorylation of their C-terminal tail by their tyrosine kinase domain. Phosphorylation then triggers interaction with adaptor proteins and activation of signaling pathways, mainly Ras/MAPK and Akt/PI3K. Those pathways control cell proliferation, motility and resistance to apoptosis. Contrary to ErbB1/3/4, ErbB2 can dimerize without any ligand. Understanding other mechanisms of regulation of its tyrosine phosphorylation and of its interactions is thus particularly interesting.ErbB2 structure and function have been extensively studied. This has led to the development of several FDA-approved targeted drugs, that are effective but to which resistance occurs, amongst which the Trastuzumab antibody that targets ErbB2 extracellular domain. The C-terminal tail of ErbB2 (CtErbB2) has been widely ignored in these studies. Since it is intrinsically disordered, the concepts and tools to study it have only emerged in the last few years.In the present work, I have performed the structural and dynamic study of CtErbB2. I showed that despite its lack of any stable structure, this proline-rich region exhibits several transient secondary structures and a long-range contact that might participate in the regulation of its intra- and inter-molecular interactions. Then, I characterized the adaptor protein Grb2, which is a partner of ErbB2 that is essential for the activation of the MAPK pathway. The solution organization of the domains of this modular protein in its apo-form was unknown so far. I also studied the interaction between Grb2 and CtErbB2, showing that in addition to the known SH2-phosphotyrosine interaction, a polyproline motif of CtErbB2 binds to the N-terminal SH3 domain of Grb2. Finally, I implemented several strategies to phosphorylate CtErbB2 tyrosines, to study more extensively the effect of phosphorylation on the whole tail.
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Louise Pinet. Structural and functional investigation of the C-terminal intrinsically disordered fragment of ErbB2. Biomolecules [q-bio.BM]. Université Paris-Saclay, 2019. English. ⟨NNT : 2019SACLS375⟩. ⟨tel-02391272⟩

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