GPCR Selectivity Beyond the Receptor
- Yamina Berchiche
- 10 hours ago
- 4 min read
Biased signaling frameworks centered on receptor conformations have a structural limitation when selectivity is also encoded at the level of receptor–transducer complex assembly.
The degree to which intracellular interfaces contribute to coupling specificity varies across receptors — from broadly promiscuous systems such as NTSR1 to more restricted receptors such as 5-HT2A — and the composition and stability of those complexes shapes downstream signaling in ways that conformation-centric models do not fully account for.
Separately, signaling outputs derived from heterologous systems often fail to reflect the biological environments they aim to represent. iPSC-derived cells, organoids, and biosensor-based assays introduce models that better preserve tissue and disease context, and the translational interpretation of receptor pharmacology shifts accordingly. Both layers are examined in the April live sessions with our expert instructors.
GPCR Allosteric Modulators as Intracellular Molecular Glues
Standard models attribute signaling specificity to ligand-stabilized receptor conformations; this framework does not fully account for selectivity that emerges from how receptor–effector assemblies are formed and maintained at the cytoplasmic interface.
Intracellular allosteric modulators engage this interface directly. SBI-553 at NTSR1 functions as a PAM-agonist for arrestin while modulating G protein selectivity through simultaneous interactions with both the receptor and Gαo. PCO371 at PTH1R promotes G protein signaling while inhibiting arrestin recruitment through intracellular binding. Examples spanning GPCR families A, B, and T suggest that interface-directed modulation may represent a broader mechanistic strategy worth exploring as a molecular glue framework.
The consequences for coupling specificity differ across receptor systems. NTSR1 couples broadly across multiple G protein families, while 5-HT2A operates with more restricted coupling behavior. These differences shape how intracellular modulators behave and what their mechanistic significance reveals about the role of cytoplasmic interfaces in signaling control.
This session with Bryan Roth will cover on how intracellular modulation controls G protein and arrestin coupling across receptors with distinct effector profiles, and whether the molecular glue framing offers a productive framework for targeting gain- and loss-of-function diseases involving GPCRs and transducers.
April 9, 2026, 10 AM EST.
Key implications:
SBI-553 illustrates how arrestin signaling can be stabilized through direct receptor–Gαo interface engagement rather than distal conformational effects
PCO371 shows that G protein bias can be achieved through intracellular binding that suppresses arrestin recruitment at PTH1R
Interface-directed ligands across GPCR families A, B, and T introduce a second control layer for selectivity alongside receptor conformations
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Purinergic GPCR Ligand Design: A3AR and P2Y14 in Neuropathic Pain
A3AR and P2Y14 represent mechanistically distinct yet convergent targets in neuropathic pain and inflammation. A3AR agonism reduces chronic pain through multimodal mechanisms, normalizing cytokine balance and reducing opioid tolerance. P2Y14, activated by UDP-sugars as a DAMP receptor, is targeted through antagonism. Together they illustrate how purinergic pharmacology approaches inflammatory pathology from two directions.
This session with Kenneth Jacobson and Matteo Pavan examines the structural determinants that make selective ligand design possible at each receptor. Originally recorded March 12.
You will walk away understanding:
How conformational constraint of a ligand scaffold, illustrated through ribose bias toward the North pseudorotational state, drives receptor subtype selectivity
How lipid-exposed intracellular allosteric sites at A3AR operate independently of the orthosteric pocket, with implications for PAM design across GPCRs
How P2Y14 antagonists achieve selectivity through minimally orthosteric anchoring at a conserved arginine residue, distinct from agonist recognition
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iPSC-Derived Systems for GPCR Signaling and Translation
Tired of HEK293 cells as a model for drug discovery?
So is Dr. Terry Hébert.
HEK293 systems are powerful tools for scalable pharmacological screening, but they have a structural limitation when signaling outcomes depend on cell type, signaling complex assembly, and disease biology.
This session with Terry Hébert will cover how patient-derived induced pluripotent stem cells (iPSCs), iPSC-derived cardiomyocytes, organoid systems, and biosensor-based assays extend GPCR pharmacology into disease-relevant environments, with dilated cardiomyopathy as a concrete model system.
April 16, 2026, 10 AM EST.
Key implications:
Signaling outputs depend on biological context, not only receptor pharmacology
iPSC and organoid models enable alignment between signaling profiles and disease-relevant phenotypes
Translational interpretation shifts when the cellular environment is preserved
Premium Members get live access, full replay, and year-round ecosystem access.
Quick Links
GPCR Antibody Validation in Real Systems → Request GeneTex samples
Biased Signaling Microcircuits in Drug Discovery → Read DiscoverX article
A2A Fluorescent Competitive Binding with NanoBRET® → Explore assay approach
This Week's Scientific Highlight
Location-biased β-arrestin conformations direct GPCR signaling
Location-biased β-arrestin conformations direct GPCR signaling. β-Arrestin 1 and β-arrestin 2 adopt distinct conformations across subcellular locations at AT1R in response to angiotensin II and the biased agonist TRV023, producing different ERK activation profiles. A population of receptor-free, activated β-arrestins at the plasma membrane promotes ERK activation independently of G proteins.
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