Dr. Terry Hebert: How Cellular Background and Localization Influence GPCR Function

Scientific Abstract

Most of what we know about GPCR signaling was learned in HEK293 cells — a system that reveals what is possible but not necessarily what is happening. This conversation with Dr. Terry Hebert confronts that gap directly.

Dr. Hebert's research focuses on the angiotensin AT1 receptor, a signaling hub coupled to Gq, Gi, G12, and beta-arrestin simultaneously — far exceeding the simple binary framework that guided a biased agonist into a failed clinical trial. His lab develops BRET- and FRET-based biosensors that produce different conformational outputs depending on the cell type, and is now deploying them in iPSC-derived cardiomyocytes and patient-specific stem cell models.

The discussion also explores GPCRs beyond the cell surface — including caged ligands designed to drug receptors on the nuclear membrane, and the unexpected discovery that G-proteins may act as transcriptional regulators. For Dr. Hebert, three decades in the wrong cellular background was reason enough to start over.

About the Guest

Dr. Terry Hebert is a Professor of Pharmacology and Therapeutics at McGill University. His research centers on GPCR signaling networks, biosensor development, and the role of cellular context in receptor pharmacology. Trained in microbiology and ion channel biology at the University of Toronto, he transitioned to GPCRs during his postdoctoral work with Michel Bouvier. His lab develops resonance energy transfer-based biosensors and applies them in induced pluripotent stem cells to study receptor function in physiologically relevant settings. His contributions span GPCR dimerization, nuclear receptor signaling, and the emerging role of G-proteins as transcriptional regulators.

Scientific Themes of the Conversation

1. Cellular Context as the Missing Variable — Why receptor pharmacology measured in HEK293 cells may not reflect what happens in native tissues, and how biosensors reveal cell-type-dependent signaling outputs.
   

2. Beyond the Gq/Beta-Arrestin Dichotomy — The AT1 receptor couples to Gq, Gi, G12, and beta-arrestin simultaneously, and the clinical failure of a biased agonist exposed the cost of oversimplifying that signaling landscape.
   

3. iPSC-Derived Models for GPCR Drug Discovery — Using induced pluripotent stem cells differentiated into cardiomyocytes, fibroblasts, and patient-specific cell types to study receptor signaling in disease-relevant backgrounds.
   

4. Intracellular GPCRs as Drug Targets — Receptors on the nuclear and mitochondrial membranes represent an untapped pharmacological frontier, and caged ligands offer a route to drugging them selectively.
   

5. G-Proteins as Transcriptional Regulators — The observation that G-proteins enter the nucleus and interact with transcriptional machinery, suggesting functions entirely distinct from canonical cell-surface signaling.
   

6. Navigating Serendipity and Risk in Discovery — From the accidental observation of GPCR dimers to negative controls gone wrong, the role of openness to unexpected results in shaping a research program.

Key Insights from the Conversation

1. HEK Cells Show What's Possible, Not What's Happening

Dr. Hebert's biosensors produce different conformational outputs when expressed in HEK293 cells versus vascular smooth muscle cells, even when challenged with the same ligand. The implication is that cellular context fundamentally shapes receptor behavior — and most of the field's pharmacological maps were drawn in the wrong terrain.

2. The AT1 Receptor Defies Simple Classification

The angiotensin AT1 receptor is not just a Gq-coupled receptor with a beta-arrestin side story. It couples to Gi, G12, and likely additional pathways. Dr. Hebert describes it as an interaction hub wired into networks whose full scope remains unknown — a receptor whose complexity scales with every new cell type examined.

3. A Clinical Trial Failure That Pointed Forward

The Trevena biased agonist for the AT1 receptor failed in clinical trials, meeting none of its primary endpoints. Dr. Hebert argues this was not a failure of the concept but of incomplete pharmacological characterization — the ligand activated more pathways than assumed. He views it as a starting point, not an ending.

4. Knocking Out G-Proteins Reveals Cellular Rewiring

When individual G-proteins are knocked out in HEK293 cells, the cells rewire their signaling networks to compensate. This means the knockout cell is intrinsically different from the wild-type — complicating any conclusions drawn from loss-of-function experiments in immortalized lines.

5. Patient-Derived iPSCs Open the Door to Personalized GPCR Pharmacology

Dr. Hebert's lab is transitioning to iPSC-derived cardiomyocytes and fibroblasts, including cells from patients with cardiomyopathies. The goal is to test therapeutic strategies targeting the AT1R, alpha-adrenergic, and beta-adrenergic systems in individual patient contexts before clinical intervention.

6. Drugging GPCRs on the Nuclear Membrane

GPCRs are not confined to the cell surface. Dr. Hebert's lab developed caged ligands that cross the plasma membrane and are uncaged intracellularly, enabling selective activation of receptors on the nuclear membrane — a moment he describes as one of the most exciting in his career.

7. Discovery Requires Being Open to Being Wrong

Dr. Hebert's advice to young scientists: embrace the complexity that intimidates your mentors. His own career was shaped by serendipitous observations — GPCR dimers that no one expected, negative controls that turned out to be discoveries. The pattern is consistent: the most important findings came from results that initially looked like mistakes.

Episode Timeline

Timestamps were generated using AI for readability.

• 00:00 Introduction

• 01:49 From microbiology to membrane proteins — Dr. Hebert's path to GPCRs

• 03:26 The angiotensin AT1 receptor — a favorite and a mystery

• 05:05 Why the Gq/beta-arrestin dichotomy broke down — the Trevena trial and its aftermath

• 07:15 Cellular context as the elephant in the room — biosensors revealing cell-type-dependent outputs

• 10:54 Building the toolkit — biosensors, iPSC-derived models, and patient-specific cells

• 18:44 Industry partnerships and the path from bench to pharma engagement

• 22:44 Intracellular GPCRs — drugging receptors on the nuclear membrane

• 26:21 Advice to young scientists — the unexpected result that redirected the project

• 27:49 Three aha moments that reshaped a career: dimers, nuclear GPCRs, and G-proteins as transcriptional regulators

Selected Quotes

About this episode

Dr. Terry Hébert wanted to be a microbiologist. Instead, he ended up getting interested in membrane protein as he followed the biology of a bacterial toxin that affects a mammalian ion channel. Today he and his team are working on understanding receptor signaling in specialized cellular environments to gain a better grasp of receptor function in pathophysiological settings with a special interest in the cardiovascular system. His favorite GPCR is the angiotensin 1 receptor, especially for its ability to activate a large variety of signaling pathways. Terry is also very active on social media. With over 2000 followers on Facebook and Twitter, he shares the latest available information on GPCR research daily.

Dr. Terry Hébert on the web

• Institute of Health Sciences Education

• Hébert Lab

• LinkedIn

• Facebook

• GPCR Consortium

• PubMed

• Dr. GPCR Ecosystem