Single-molecule dynamics of GPCR signal transducers

G protein-coupled receptors (GPCRs) transduce extracellular signals across the plasma membrane by coupling to heterotrimeric G proteins and arrestins. G proteins activate intracellular signaling cascades, while arrestins primarily attenuate G protein signaling and facilitate GPCR internalization and trafficking. Advances in structural biology have significantly improved our understanding of the molecular mechanisms underlying GPCR signal transduction by capturing distinct conformational states adopted by G proteins and arrestins along their activation pathways. However, a full understanding of GPCR-mediated signaling requires elucidating the dynamic interconversions between these metastable states and the conformational energy landscapes that govern them. In this work, I use single-molecule Förster resonance energy transfer (smFRET) imaging to investigate the dynamics of G proteins and arrestins during key stages of their activation by GPCRs. Chapter 2 focuses on the movements of the G protein α-helical domain, which undergoes displacement upon receptor coupling to facilitate nucleotide exchange and G protein activation. I show that these dynamics are affected by the agonist bound in the receptor's orthosteric pocket, suggesting a previously unrecognized role for the G protein in shaping ligand efficacy. Chapter 3 explores the autoinhibitory C-tail dynamics of a non-visual β-arrestin, identifying an intermediate conformational state that enables its recruitment to receptors with minimal or no C-terminal phosphorylation. Together, these single-molecule studies provide new insights into how both the initiation and termination of GPCR signaling are fine-tuned through the allosteric modulation of its transducer proteins’ structural dynamics.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biophysics & Quant Biology

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Deutsch, Jonathan C.

Contributors dc:contributor

• Kobilka, Brian
• Schroeder, Charles
• Gruebele, Martin
• Shukla, Diwakar

• GPCRs
• single molecule
• dynamics.

Statement dc:rights

• Copyright 2025 Jonathan Deutsch

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129490

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129490