bims-dicesi 2025-01-19 papers

Issue of 2025–01–19
four papers selected by
Ashanika Karandawela

J Cell Sci. 2025 Jan 01. pii: JCS263434. [Epub ahead of print]138(1):

Quantitative approaches for studying G protein-coupled receptor signalling and pharmacology.

Abigail Pearce, Theo Redfern-Nichols, Edward Wills, Matthew Rosa, Iga Manulak, Claudia Sisk, Xianglin Huang, Peace Atakpa-Adaji, David L Prole, Graham Ladds.

G protein-coupled receptor (GPCR) signalling pathways underlie numerous physiological processes, are implicated in many diseases and are major targets for therapeutics. There are more than 800 GPCRs, which together transduce a vast array of extracellular stimuli into a variety of intracellular signals via heterotrimeric G protein activation and multiple downstream effectors. A key challenge in cell biology research and the pharmaceutical industry is developing tools that enable the quantitative investigation of GPCR signalling pathways to gain mechanistic insights into the varied cellular functions and pharmacology of GPCRs. Recent progress in this area has been rapid and extensive. In this Review, we provide a critical overview of these new, state-of-the-art approaches to investigate GPCR signalling pathways. These include novel sensors, Förster or bioluminescence resonance energy transfer assays, libraries of tagged G proteins and transcriptional reporters. These approaches enable improved quantitative studies of different stages of GPCR signalling, including GPCR activation, G protein activation, second messenger (cAMP and Ca2+) signalling, β-arrestin recruitment and the internalisation and intracellular trafficking of GPCRs.

Keywords: BRET; Ca2+ signalling; Cell signalling; FRET; GPCRs; IP3; cAMP

DOI: https://doi.org/10.1242/jcs.263434

Nat Commun. 2025 Jan 13. 16(1): 619

Conformational diversity in class C GPCR positive allosteric modulation.

Giuseppe Cannone, Ludovic Berto, Fanny Malhaire, Gavin Ferguson, Aurelien Fouillen, Stéphanie Balor, Joan Font-Ingles, Amadeu Llebaria, Cyril Goudet, Abhay Kotecha, Vinothkumar K R, Guillaume Lebon.

The metabotropic glutamate receptors (mGlus) are class C G protein-coupled receptors (GPCR) that form obligate dimers activated by the major excitatory neurotransmitter L-glutamate. The architecture of mGlu receptor comprises an extracellular Venus-Fly Trap domain (VFT) connected to the transmembrane domain (7TM) through a Cysteine-Rich Domain (CRD). The binding of L-glutamate in the VFTs and subsequent conformational change results in the signal being transmitted to the 7TM inducing G protein binding and activation. The mGlu receptors signal transduction can be allosterically potentiated by positive allosteric modulators (PAMs) binding to the 7TMs, which are of therapeutic interest in various neurological disorders. Here, we report the cryoEM structures of metabotropic glutamate receptor 5 (mGlu5) purified with three chemically and pharmacologically distinct PAMs. We find that the PAMs modulate the receptor equilibrium through their different binding modes, revealing how their interactions in the 7TMs impact the mGlu5 receptor conformational landscape and function. In addition, we identified a PAM-free but agonist-bound intermediate state that also reveals interactions mediated by intracellular loop 2. The activation of mGlu5 receptor is a multi-step process in which the binding of the PAMs in the 7TM modulates the equilibrium towards the active state.

DOI: https://doi.org/10.1038/s41467-024-55439-9

bioRxiv. 2025 Jan 02. pii: 2024.12.31.630923. [Epub ahead of print]

Structure of an LGR dimer - an evolutionary predecessor of glycoprotein hormone receptors.

Zhen Gong, Shuobing Chen, Ziao Fu, Brian Kloss, Chi Wang, Oliver B Clarke, Qing R Fan, Wayne A Hendrickson.

The glycoprotein hormones of humans, produced in the pituitary and acting through receptors in the gonads to support reproduction and in the thyroid gland for metabolism, have co-evolved from invertebrate counterparts 1,2 . These hormones are heterodimeric cystine-knot proteins; and their receptors bind the cognate hormone at an extracellular domain and transmit the signal of this binding through a transmembrane domain that interacts with a heterotrimeric G protein. Structures determined for the human receptors as isolated for cryogenic electron microscopy (cryo-EM) are all monomeric 3-6 despite compelling evidence for their functioning as dimers 7-10 . Here we describe the cryo-EM structure of the homologous receptor from a neuroendocrine pathway that promotes growth in a nematode 11 . This structure is an asymmetric dimer that can be activated by the hormone from that worm 12 , and it shares features especially like those of the thyroid stimulating hormone receptor (TSHR). When studied in the context of the human homologs, this dimer provides a structural explanation for the transactivation evident from functional complementation of binding-deficient and signaling-deficient receptors 7 , for the negative cooperativity in hormone action that is manifest in the 1:2 asymmetry of primary TSH:TSHR complexes 8,9 , and for switches in G-protein usage that occur as 2:2 complexes form 9,10 .

DOI: https://doi.org/10.1101/2024.12.31.630923

J Am Chem Soc. 2025 Jan 13.

Key Interaction Changes Determine the Activation Process of Human Parathyroid Hormone Type 1 Receptor.

Yue Zhang, Qingchuan Zheng, Arieh Warshel, Chen Bai.

The parathyroid hormone type 1 receptor (PTH1R) plays a crucial role in modulating various physiological functions and is considered an effective therapeutic target for osteoporosis. However, a lack of detailed molecular and energetic information about PTH1R limits our comprehensive understanding of its activation process. In this study, we performed computational simulations to explore key events in the activation process, such as conformational changes in PTH1R, Gs protein coupling, and the release of guanosine diphosphate (GDP). Our analysis identified kinetic information, including the rate-determining step, transition state, and energy barriers. Free-energy and structural analyses revealed that GDP could be released from the Gs protein when the binding cavity is partially open. Additionally, we predicted important residues, including potential pathogenic mutations, and verified their significance through site-directed mutations. These findings enhance our understanding of class B GPCR activation mechanisms. Furthermore, the methodology employed in this study can be applied to other biophysical systems.

DOI: https://doi.org/10.1021/jacs.4c15025