GPCR Biased Signaling and Molecular Glues
- Yamina Berchiche
- 21 hours ago
- 3 min read
GPCR allosteric modulators as novel intracellular molecular glues
Classic models explain biased signaling through ligands that stabilize receptor conformations and favor selective transducer interactions. This Masterclass with Bryan Roth examines an additional mechanism: intracellular modulators that bind directly at receptor–transducer interfaces.
Examples such as SBI-553 at NTSR1 and PCO371 at PTH1R, already characterized, provide concrete cases where ligands engage both receptor and transducer. SBI-553 functions as a PAM-agonist for arrestin while modulating G protein engagement through direct interaction with NTSR1 and Gαo. PCO371 promotes G protein signaling while inhibiting arrestin recruitment through intracellular binding.
These systems are used here as resolved examples of how interface binding can stabilize specific signaling complexes alongside receptor conformation-based mechanisms.
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 introduce a second control layer for selectivity alongside receptor conformations.
Join us live, April 9, 2026, 10 am EST.
This live session with recording available as well as all masterclasses are now included in Premium.
iPSC-Derived Systems for GPCR Signaling and Translation
Heterologous systems such as HEK293 cells enable scalable pharmacological assays, but they simplify the cellular context in which GPCR signaling occurs. This limits how signaling data can be interpreted when receptor behavior depends on cell type, signaling complex assembly, and disease biology.
This session with Terry Hébert examines how iPSC-derived cardiomyocytes, organoid systems, and biosensor-based assays extend GPCR pharmacology into more physiologically relevant environments.
iPSC-derived cardiomyocytes allow signaling to be studied in disease contexts such as dilated cardiomyopathy. Organoid systems introduce multicellular organization, while biosensor-based approaches enable direct monitoring of signaling pathways within these systems.
Key implications:
iPSC-derived cardiomyocytes reveal GPCR signaling behaviors that differ from HEK293-based systems, particularly in disease-relevant contexts.
Organoid models incorporate cellular architecture that affects receptor signaling and pathway integration.
Biosensor-based assays enable direct measurement of signaling dynamics within complex biological systems.
Join us live, April 16, 2026, 10 am EST.
This live session with recording available as well as all masterclasses are now included in Premium.
GPCR Pharmacology: Open Problems and Discussion
Binding assays and functional assays are often treated as complementary readouts of the same interaction. This framework has a structural limitation: binding measures the receptor population that engages tracer ligands, while functional assays measure the receptor population that couples to signaling pathways.
This AMA examines how these formats diverge, particularly for allosteric ligands, where efficacy can change without measurable shifts in affinity.
Key implications:
Binding and function probe different receptor populations, so discrepancies are expected rather than anomalous.
Allosteric modulators can alter signaling efficacy without changing ligand affinity, uncoupling binding readouts from functional outcomes.
Interpreting mode of action requires aligning assay format with the specific receptor state being measured.
March 26, 12 pm EST. Access provided via newsletter signup.
Quick Links
Antibody validation continues to constrain GPCR targeting and reagent confidence. Read article ➤
Biased signaling can also be framed as circuit-level organization rather than binary switching. Read analysis ➤
Computational descriptions of ligand bias remain central to linking structural motion with signaling selectivity. Listen now ➤
GPCR signaling also controls insect behaviors such as blood feeding and mating in ways that broaden how receptor biology is studied. Explore discussion ➤
This Week’s Scientific Highlight
GPR61, implicated in appetite and body weight regulation, is inhibited by inverse agonists that bind an induced intracellular allosteric pocket, disrupting receptor–G protein interactions and abolishing constitutive activity through a direct interface mechanism.
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Dr. GPCR brings together scientists working across GPCR biology, pharmacology, and drug discovery to examine how signaling mechanisms are measured and applied.
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