Conformational Changes in Tyrosine 11 of Neurotensin Are Required to Activate the Neurotensin Receptor 1

Fabian Bumbak; Trayder Thomas; Billy J Noonan-Williams; Tasneem M Vaid; Fei Yan; Alice R Whitehead; Shoni Bruell; Martina Kocan; Xuan Tan; Margaret A Johnson; Ross A D Bathgate; David K Chalmers; Paul R Gooley; Daniel J Scott

doi:10.1021/acsptsci.0c00026

Conformational Changes in Tyrosine 11 of Neurotensin Are Required to Activate the Neurotensin Receptor 1

ACS Pharmacol Transl Sci. 2020 Apr 29;3(4):690-705. doi: 10.1021/acsptsci.0c00026. eCollection 2020 Aug 14.

Authors

Fabian Bumbak^{1

2

3}, Trayder Thomas⁴, Billy J Noonan-Williams⁴, Tasneem M Vaid^{2

3

1}, Fei Yan^{2

3}, Alice R Whitehead¹, Shoni Bruell¹, Martina Kocan^{1

5}, Xuan Tan⁶, Margaret A Johnson⁶, Ross A D Bathgate^{1

2}, David K Chalmers⁴, Paul R Gooley^{2

3}, Daniel J Scott^{1

2}

Affiliations

¹ The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria 3010, Australia.
² Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, Victoria 3010, Australia.
³ Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia.
⁴ Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia.
⁵ The School of BioSciences, The University of Melbourne, Parkville, Victoria 3010, Australia.
⁶ Department of Chemistry, The University of Alabama at Birmingham, Birmingham, Alabama 35294-1240, United States.

Abstract

Cell-cell communication via endogenous peptides and their receptors is vital for controlling all aspects of human physiology and most peptides signal through G protein-coupled receptors (GPCRs). Disordered peptides bind GPCRs through complex modes for which there are few representative crystal structures. The disordered peptide neurotensin (NT) is a neuromodulator of classical neurotransmitters such as dopamine and glutamate, through activation of neurotensin receptor 1 (NTS₁). While several experimental structures show how NT binds NTS₁, details about the structural dynamics of NT during and after binding NTS₁, or the role of peptide dynamics on receptor activation, remain obscure. Here saturation transfer difference (STD) NMR revealed that the binding mode of NT fragment NT10-13 is heterogeneous. Epitope maps of NT10-13 at NTS₁ suggested that tyrosine 11 (Y11) samples other conformations to those observed in crystal structures of NT-bound NTS₁. Molecular dynamics (MD) simulations confirmed that when NT is bound to NTS₁, residue Y11 can exist in two χ₁ rotameric states, gauche plus (g⁺) or gauche minus (g^-). Since only the g⁺ Y11 state is observed in all the structures solved to date, we asked if the g^- state is important for receptor activation. NT analogues with Y11 replaced with 7-OH-Tic were synthesized to restrain the dynamics of the side chain. P(OH-TIC)IL bound NTS₁ with the same affinity as NT10-13 but did not activate NTS₁, instead acted as an antagonist. This study highlights that flexibility of Y11 in NT may be required for NT activation of NTS₁.