Single Molecule Analysis of Functionally Asymmetric G Protein-coupled Receptor (GPCR) Oligomers Reveals Diverse Spatial and Structural Assemblies |
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Authors: | Kim C. Jonas Francesca Fanelli Ilpo T. Huhtaniemi Aylin C. Hanyaloglu |
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Affiliation: | From the ‡Institute of Reproductive and Developmental Biology, Department of Surgery and Cancer, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom.;the §Computational Structural Biology Lab, Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 183-41100 Modena, Italy, and ;the ¶Institute for Biomedicine, Department of Physiology, University of Turku, 20520 Turku, Finland |
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Abstract: | Formation of G protein-coupled receptors (GPCRs) into dimers and higher order oligomers represents a key mechanism in pleiotropic signaling, yet how individual protomers function within oligomers remains poorly understood. We present a super-resolution imaging approach, resolving single GPCR molecules to ∼8 nm resolution in functional asymmetric dimers and oligomers using dual-color photoactivatable dyes and localization microscopy (PD-PALM). PD-PALM of two functionally defined mutant luteinizing hormone receptors (LHRs), a ligand-binding deficient receptor (LHRB−) and a signaling-deficient (LHRS−) receptor, which only function via intermolecular cooperation, favored oligomeric over dimeric formation. PD-PALM imaging of trimers and tetramers revealed specific spatial organizations of individual protomers in complexes where the ratiometric composition of LHRB− to LHRS− modulated ligand-induced signal sensitivity. Structural modeling of asymmetric LHR oligomers strongly aligned with PD-PALM-imaged spatial arrangements, identifying multiple possible helix interfaces mediating inter-protomer associations. Our findings reveal that diverse spatial and structural assemblies mediating GPCR oligomerization may acutely fine-tune the cellular signaling profile. |
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Keywords: | Bioluminescence Resonance Energy Transfer (BRET) Cell Signaling G Protein G protein-Coupled Receptor (GPCR) Structural Biology Dimer Oligomer Super-resolution Imaging |
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