G protein-coupled signal transduction systems

Hébert Lab, Department of Pharmacology and Therapeutics, McGill University


Research in my lab is is centered broadly around the theme of G protein-coupled signal transduction systems. These signalling systems are activated by agonists that bind to G protein-coupled receptors (GPCRs, alternatively we use the term heptahelical receptor or 7TM-Rs) leading to the regulation of effector proteins (e.g. enzymes and ion channels) by a transducer. We are interested in 1) novel signalling complexes and pathways associated with alternative subcellular localization of GPCRs and G proteins and how they might be involved in a rare neurodevelopmental disorder, 2) designing and validating biosensors to track signalling events and allosteric modulation of GPCRs. 3) measuring such events in primary cells, inducible pluripotent stem cells, and in living animals, and 4) basic mechanisms of how GPCR signalling systems are wired, and the roles that these architectural features of signalling complex design might play in cardiovascular and neurodegenerative diseases. These projects are currently funded by CIHR, MITACS and the Weston Brain Institite.


 1) Alternate subcellular destinations for 7TM-R signalling complexes.

In recent years we have come to realize that the cell surface is not the only site where 7TM-Rs are functional. These receptors, and perhaps more interestingly, fragments derived by regulated proteolytic events as well as their associated signalling machinery have functions in other cellular compartments including the ER, Golgi and nuclear membranes. An increasing number of 7TM-Rs have also been demonstrated to be targetted to the endomembrane locations as have their associated signalling molecules. Several lines of investigation led us to an interest in signalling by internal GPCRs. More recently we have been studying how G proteins might be transcriptional regulators during the cardiac fibrotic response and more generally how such signalling might be understood and used for drug discovery in cardiovascular disease.


2) Developing biosensors to track GPCR signalling. 

Over the past few years, we have helped conceive, design, produce and validate over BRET-based biosensors to track receptor signalling by measuring activation of heterotrimeric G proteins, downstream effectors, production of second messengers and the recruitment of GPCR-interacting proteins  as well as conformational biosensors to how cellular environment influences readout from different biosensor platforms, i.e. whether our different platforms are “portable” from cell type to cell type. The latter set of conformational biosensors do not require any knowledge of downstream signalling events and will complement signalling biosensors in this regard as we move across different cell types.



3) Moving biosensors into mor relevant physiological contexts.

Although technical prowess to screen for drugs has increased dramatically, translation into the clinic has stagnated. This is likely due to 1) our rudimentary understanding of disease mechanisms, and 2) our increasing use of generic, cell-based screens (using heterologous systems such as HEK 293 cells) which have moved us away from biologically relevant tissues, organs and patients. To optimize integration of pharmacological screening data and the translational outputs from such research for both common and rare diseases, we need a richer and more complete understanding of patients in the real world. Our goal here is to develop better preclinical models linking clinical samples with drug screening technologies and use patient-derived inducible pluripotent stem cells (iPSCs) and ultimately organoids, which will feed the disruptive development of personalized treatment with better outcomes for patients, through improved understanding of individualized disease mechanisms and therapeutic responses, new molecular diagnostics and targeted therapies. We have adopted a number of approaches including using adeno-associated versions of our current biosensor panels in patient-derived cells and also in primary cells isolated from animals and more recently in the brains of intact behaving animals.


4) Hard-wiring of 7TM-R signalling complexes.
Some 7TMs regulate the activity of multiple effectors. The majority of drugs that target G protein-coupled signal transduction systems act at ligand binding sites. A therapeutic strategy may require regulating the activity of a specific effector, but drugs aimed at 7TMs coupled to multiple effectors obviously lack specificity in this regard, and produce undesirable side effects. Thus, a primary objective of our research is to identify peptide motifs involved in specific protein-protein interactions yielding a novel strategy for therapeutic intervention- the modulation of specific receptor complexes by disrupting the interactions which lead to their formation and trafficking or augmenting interactions that lead to signal transduction with peptidic or peptidomimetic compounds.