CRISPR/Cas9, NanoBRET and GPCRs: A Bright Future for Drug Discovery

GPCRs

G protein-coupled receptors (GPCRs) are a large family of receptors that traverse the cell membrane seven times. Functionally, GPCRs are extremely diverse, yet they contain highly conserved structural regions. GPCRs respond to a variety of signals, from small molecules to peptides and large proteins. Many GPCRs are involved in disease pathways and, not surprisingly, they present attractive targets for both small-molecule and biologic drugs.

In response to a signal, GPCRs undergo a conformational change, triggering an interaction with a G protein—a specialized protein that binds GDP in its inactive state or GTP when activated. Typically, the GPCR exchanges the G protein-bound GDP molecule for a GTP molecule, causing the activated G protein to dissociate into two subunits that remain anchored to the cell membrane. These subunits relay the signal to various other proteins that interact with or produce second-messenger molecules. Activation of a single G protein can result, ultimately, in the generation of thousands of second messengers.

Given the complexity of GPCR signaling pathways and their importance to human health, a considerable amount of research has been devoted to GPCR interactions, both with specific ligands and G proteins. Continue reading “CRISPR/Cas9, NanoBRET and GPCRs: A Bright Future for Drug Discovery”

Executing a NanoBRET™ Experiment: From Start to Data

This is a guest post from Katarzyna Dubiel, marketing intern in Cellular Analysis and Proteomics.

“The objective of my experiment was to test the NanoBRET™ assay as if I was a customer, independent of the research and development team which develops the assay.”

Designing and implementing a new assay can be a challenging process with many unexpected troubleshooting steps. We wanted to know what major snags a scientist new to the NanoBRET™ Assay would encounter. To determine this, we reached out to Laurence Delauriere, a senior applications scientist at Promega-France, who had never previously performed a NanoBRET™ assay. Laurence went step-by-step through the experimental process looking at the CRAF-BRAF interaction in multiple cell lines. In an interview, Laurence provided us with some tips and insights from her work implementing the new NanoBRET™ assay.

In a few words, can you explain NanoBRET?
“NanoBRET is used to monitor protein: protein interactions in live cells. It is a bioluminescence resonance energy transfer (BRET) based assay that uses NanoLuc® luciferase as the BRET energy donor and HaloTag® protein labeled with the HaloTag® NanoBRET™ 618 fluorescent ligand as the energy acceptor to measure the interaction of two binding partners.” Continue reading “Executing a NanoBRET™ Experiment: From Start to Data”

Kinase Inhibitors as Therapeutics: A Review

This blog was originally published in April of 2018. This update includes the paper, “Quantitative, Wide-Spectrum Kinase Profiling in Live Cells for Assessing the Effect of Cellular ATP on Target Engagement” from Cell Chemical Biology, demonstrating the power of NanoBRET™ target engagement kinase assays in the study of kinase inhibitors.

The review “Kinase Inhibitors: the road ahead” was recently published in Nature Reviews Drug Discovery. In it, authors Fleur Ferguson and Nathanael Gray provide an up-to-date look at the “biological processes and disease areas that kinase-targeting small molecules are being developed against”. They note the related challenges and the strategies and technologies being used to efficiently generate highly-optimized kinase inhibitors.

This review describes the state of the art for kinase inhibitor therapeutics. To understand why kinase inhibitors are so important in the development of cancer (and other) therapeutics research, let’s start with the role of kinases in cellular physiology.

The road ahead for kinase inhibitor studies.

Why Kinases? Continue reading “Kinase Inhibitors as Therapeutics: A Review”

A NanoBRET™ Biosensor for GPCR:G protein Interaction with the Kinetics and Temporal Resolution of Patch Clamping

Electrophysiologists are talented scientists/artists who see into the events of the cell with amazing detail.
Electrophysiology experiments provide a view into the cell with amazing detail. The paper reviewed here describes a molecular reporter biosensor (NanoBRET) that can offer the same kind of temporal and spatial resolution traditionally reserved for extremely labor-intensive experiments like patch clamp analysis.

I confess that I struggled through biophysics, and my Bertil Hille textbook Ion Channels of Excitable Membranes lies neglected somewhere in a box in my basement (I have not tossed it into the recycle bin—I can’t bear too, I spent too much time bonding with that book in graduate school).

My struggles in that graduate class and my attendance at the seminars of my grad school colleagues who were conducting electrophysiological studies left me with a sincere awe and appreciation of both the genius and the artistry required to produce nice electrophysiology data. The people who are good at these experiments are artists—they have the golden touch when it comes to generating that megaohm seal between a piece of cell membrane and a finely pulled glass pipette. And, they are brilliant scientists, they really understand the physics, the chemistry and the biology of the cells they study from a perspective that very few scientists ever develop.

Electrophysiology data, which often demonstrate the gating of a single channel protein in response to a single stimulus in real time–ions crossing a membrane through a single protein–are amazing for their ability, unlike virtually any other experimental data for the story they can tell about what is going on in a cell in real time under physiological conditions.

So when I read the paper recently published by Mashuo et al. in Science SignalingDistinct profiles of functional discrimination among G proteins determine the action of G protein-coupled receptors”, this sentence really caught my attention:

When constructs were ectopically expressed in HEK 293T/17 cells, we obtained very similar kinetics for the GPCR-driven responses between NanoBRET™ biosensors and the patch clamp recordings.

They continue:

Indeed, the activation rates that we observed were very similar to those of GPCR-stimulated GIRKs [G protein-coupled, inwardly rectifying K+ channel] in native cells, suggesting that the conditions of this assay closely match the in vivo setting. This finding further demonstrates the ability of the system to resolve the fast, physiological relevant kinetics of GPCR signaling.

A reporter biosensor that can resolve events similarly to patch clamping?!  Amazing. Continue reading “A NanoBRET™ Biosensor for GPCR:G protein Interaction with the Kinetics and Temporal Resolution of Patch Clamping”