Shining Stars: Cool NanoLuc® Plasmid Constructs Available Through the Addgene Repository

Researchers having been sharing plasmids ever since there were plasmids to share. Back when I was in the lab, if you read a paper and saw an interesting construct you wished to use, you could either make it yourself or you could “clone by phone”.  One of my professors was excellent at phone cloning with labs around the world and had specific strategies and tactics for getting the plasmids he wanted. Addgene makes this so much easier to share your constructs from lab to lab. Promega supports the Addgene mission statement: Accelerate research and discovery by improving access to useful research materials and information.  Many of our technology platforms like HaloTag® Fusion Protein, codon-optimized Firefly luciferase genes (e.g., luc2), and NanoLuc® Luciferase are present in the repository. We encourage people to go to Addgene to get new innovative tools. Afterall, isn’t science better when we share?

I’d like to focus on some tools in the Addgene collection based on NanoLuc® Luciferase (NLuc).  The creation of NanoLuc® Luciferase and the optimal substrate furimazine is a good story (1).  From a deep sea shrimp to a compact powerhouse of bioluminescence, NLuc is 100-fold brighter than our more common luciferases like firefly (FLuc) and Renilla (RLuc) luciferase.  This is important not so much for how bright you can make a reaction but for how sensitive you can make a reaction.  NLuc requires 100-fold less protein to produce the same amount of light from a Fluc or RLuc reaction.  NLuc lets you work at physiological concentrations.  NLuc is bright enough to detect endogenous tagged genes generated through the CRISPR/Cas9 knock-in.  NLuc is very inviting for endogenous tagging as it is only 19kDa.  An example is the CRISPaint-NLuc construct (Plasmid #67178) for use in the system outlined in Schmid-Burgk, J.L. et al (2).

Two applications of NanoLuc® Technology have caught my attention through coupling the luciferase with fluorescent proteins to make better imaging reporters and biosensors. Continue reading

Making the Switch from FRET to BRET: Applications of NanoLuc® Luciferase with Fluorescent Protein Acceptors for Sensing Cellular Events

A Bioluminescent Alternative

Fluorescence resonance energy transfer (FRET) probes or sensors are commonly used to measure cellular events. The probes typically have a matched pair of fluorescent proteins joined by a ligand-binding or responsive protein domain. Changes in the responsive domain are reflected in conformational changes that either bring the two fluorescent proteins together or drive them apart. The sensors are measured by hitting the most blue-shifted fluorescent protein with its excitation wavelength (donor). The resulting emission is transferred to the most red-shifted fluorescent protein in the pair, and the result is ultimately emission from the red-shifted protein (acceptor).

As pointed out by Aper, S.J.A. et al. below, FRET sensors face challenges of photobleaching, autofluorescence, and, in the case of exciting cyan-excitable donors, phototoxicity. Another challenge to using FRET sensors comes when employing optogenetic regulators to initiate the event you wish to monitor. Optogenetic regulators respond to specific wavelengths and initiate signaling. The challenge comes when the FRET donor excitation overlaps with the optogenetic initiation wavelengths. Researchers have sought to alleviate many of these challenges by exchanging the fluorescent donor for a bioluminescent donor, making bioluminescence resonance energy transfer (BRET) probes. In the three papers described below, the authors chose NanoLuc® Luciferase as the BRET donor due to its extremely bright signal. Continue reading

Probing RGS:Gα Protein Interactions with NanoBiT Assays

gpcr_in_membrane_on_white2When I was a post-doc at UT Southwestern, I was fortunate to interact with two Nobel prize winners, Johann Deisenhofer and Fred Gilman.  Johann once helped me move a -80°C freezer into his lab when we lost power in my building. I once replaced my boss at small faculty mixer with a guest speaker and had a drink with Fred Gilman and several other faculty members from around the university. Among the faculty, one professor had a cell phone on his belt, an odd sight in 1995. Fred Gilman asked him what it was and why he had it. It was so his lab could notify him of good results anytime of the day. Fred laughed and told him to get rid of it – if it’s good data, it will survive until morning.

I was reminded of this story when I read a recent paper by Bodle, C.R. et al (1) about the development of a NanoBiT® Complementation Assay (2) to measure interactions of Regulators of G Protein Signaling (RGS) with Gα proteins in cells. (Fred Gilman was the first to isolate a G protein and that led to him being a co-recipient of the Nobel Prize in 1994). The authors created over a dozen NanoBiT Gα:RGS domain pairs and found they could classify different RGS proteins by the speed of the interaction in a cellular context. The interactions were readily reversible with known inhibitors and were suitable for high-throughput screening due to Z’ factors exceeding 0.5. The study paves the way for future work to identify broad spectrum RGS domain:Gα inhibitors and even RGS domain-specific inhibitors. This is the second paper applying NanoBiT Technology to GPCR studies (3).

A Little Background…
A primary function of GPCRs is transmission of extracellular signals across the plasma membrane via coupling with intracellular heterotrimeric G proteins. Upon receptor stimulation, the Gα subunit dissociates from the βγ subunit, initiating the cascade of downstream second messenger pathways that alter transcription (4). The Gα subunits are actually slow GTPases that propagate signals when GTP is bound but shutdown and reassociate with the βγ subunit when GTP is cleaved to GDP. This activation process is known as the GTPase cycle. G proteins are extremely slow GTPases. Continue reading

NanoBiT Assay Applied to Study Role of SOD1 in ALS

NanoBiT Protein ComplementationBack in 2015 the Ice Bucket Challenge brought Amyotrophic Lateral Sclerosis (ALS) to public attention, initiating worldwide pleas for more funding of research toward a cure for this fatal disease, which is characterized by progressive degeneration of motor neurons. In spite of many efforts over the last few decades, the precise cause of ALS is still unknown.

The complexity of the problem of ALS pathogenesis is highlighted in the review “Decoding ALS: from genes to mechanism”  published in Nature in November 2016. The review highlights a long list of genetic factors implicated in ALS, grouping them into genes affecting protein quality control, RNA stability/function, and the cytoskeletal structure of neuronal cells.

Mutations in the antioxidant enzyme superoxide dismutase (SOD1) were the first to be associated with ALS. According to the review, more than 170 SOD1 mutations causing ALS have since been identified. Many of these mutations are thought to result in misfolding of SOD1, contributing to toxicity when the misfolded protein accumulates within the cell.

A paper by Oh-hashi et al., published in Cell Biochemistry and Function in October 2016 used the NanoBiT protein complementation assay to investigate the effect of two common ALS-associated SOD1 mutations on dimerization of the SOD1 protein. Continue reading

The Role of the NanoLuc® Reporter in Investigating Ligand-Receptor Interactions

Luminescent reporter assays are powerful research tools for a variety of applications. Last March we presented a webinar on this topic, Understanding Luminescent Reporter Assay Design, which proved to enlighten many who registered. The webinar addressed the importance of careful experimental design when using a luminescent reporter such as Promega’s Firefly or NanoLuc® Luciferase.

Reporters provide a highly sensitive, quantifiable metric for cellular events such as gene expression, protein function and signal transduction. Luminescent reporters have become even more valuable for live, real-time measurement of various processes in living cells. This is backed by the fact that a growing number of scientific publications reference the use of the NanoLuc® Luciferase reporter and demonstrate its effectiveness as a reporter assay. Continue reading

Shining Light on a Superbug

Antibiotic-resistant bacteria and their potential to cause epidemics with no viable treatment options have been in the news a lot. These “superbugs,” which have acquired genes giving them resistance to common and so-called “last resort” antibiotics, are a huge concern as effective treatment options dwindle. Less attention has been given to an infection that is not just impervious to antibiotics, but is actually enabled by them.

Clostridium diffic33553646_lile Infection (CDI) is one of the most common healthcare-associated infections and a significant global healthcare problem. Clostridium difficile (C. diff), a Gram-positive anaerobic bacterium, is the source of the infection. C. diff spores are very resilient to environmental stressors, such as pH, temperature and even antibiotics, and can be found pretty much everywhere around us, including on most of the food we eat. Ingesting the spores does not usually lead to infection inside the body without also being exposed to antibiotics.

Individuals taking antibiotics are 7-10 times more likely to acquire a CDI. Antibiotics disrupt the normal flora of the intestine, allowing C. diff to compete for resources and flourish. Once exposed to the anaerobic conditions of the human gut, these spores germinate into active cells that embed into the tissue lining the colon. The bacteria are then able to produce the toxins that can cause disease and result in severe damage, or even death. Continue reading

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

NanoBiT™ Assay: Transformational Technology for Studying Protein Interactions Named a Top 10 Innovation of 2015

For three out of the last four years, we have been honored to have one of our key technologies named a Top 10 Innovation by The Scientist. This year the innovative NanoBiT™ Assay (NanoLuc® Binary Technology) received the recognition. NanoBiT™ is a structural complementation reporter based on NanoLuc® Luciferase, a small, bright luciferase derived from the deep sea shrimp Oplophorus gracilirostris.

Using plasmids that encode the NanoBiT complementation reporter, you can make fusion proteins to “report” on protein interactions that you are studying. One of the target proteins is fused to the 18kDa subunit; the other to the 11 amino acid subunit. The NanoBiT™ subunits are stable, exhibiting low self-affinity, but produce an ultra-bright signal upon association. So, if your target proteins interact, the two subunits are brought close enough to each other to associate and produce a luminescent signal. The strong signal and low background associated with a luminescent system, and the small size of the complementation reporter, all help the NanoBiT™ assay overcome the limitations associated with traditional methods for studying protein interactions.

The small size reduces the chances of steric interference with protein interactions. The ultra bright signal, means that even interactions among proteins present in very low amounts can be detected and quantified–without over-expressing large quantities of non-native fusion proteins and potentially disrupting the normal cellular environment. And the NanoBiT™ assay can be performed in real time, in live cells.

The NanoBiT™ assay is already being deployed in laboratories to help advance understanding of fundamental cell biology. You can see how one researcher is already taking full advantage of this innovative technology in the video embedded below:

Visit the Promega web site to see more examples more examples how the NanoBiT™ assay can break through the traditional limitations for studying protein interactions in cells.

You can read the Top 10 article in The Scientist here.

About the Development of an Improved BRET Assay: NanoBRET

"Protein BRD4 PDB 2oss" by Emw - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons -

“Protein BRD4 PDB 2oss” by Emw – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons –

One of the more exciting reporter molecules technologies available came online in the past year, with the launch of the Promega NanoBRET™ technology. While it’s easy for me, a science writer at Promega, to brag, seriously, this is a very cool protein interactions tool.

A few of the challenges facing protein-protein interactions researchers include:

  • The ability to quantitatively characterize protein-protein interactions
  • Ability to examine protein-protein interactions in situ, in the context of the living cell

A goal of the NanoBRET™ developers was to improve the sensitivity and dynamic range of traditional BRET technology, in order to address these challenges.

In May 2015 these researchers published an article outlining their efforts to create NanoBRET technology in ACS Chemical Biology, in an article entitled, “NanoBRET—A Novel BRET Platform for the Analysis of Protein-Protein Interactions”. Here is a brief look at their work.

Continue reading

It’s the Little Things: Celebrating NanoLuc and Other Small Things

NanoLuc dual reporters

Illustration showing NanoLuc and firefly luciferase reporters.

This month we are celebrating a small thing—NanoLuc® luciferase, an enzyme whose tiny size and bright luminescence enable much more sensitive detection of intracellular events than other bioluminescent reporters. Scaling down the size of the luciferase protein makes it “fit” in situations where larger reporters do not, and also makes it less likely to interfere with natural biology than larger proteins. Scaling up the brightness allows you to detect the reporter at low abundance, enhancing sensitivity and allowing detection of small changes in gene expression at concentrations closer to physiological levels.

These properties of Nanoluc® luciferase allow its bioluminescence to be used to detect intracellular events in ways not possible before. One example of how this small size and intense brightness are being applied to help solve biological problems is the insertion of NanoLuc® luciferase into influenza viruses, where the genome size is small and does not tolerate large insertions. Unlike viruses incorporating larger luciferases, the influenza reporters incorporating NanoLuc® luciferase are stable, retain pathogenicity and are bright enough to track at low doses during the early stages of infection (1). You can find out more about the many applications of NanoLuc® luciferase here.

In the spirit of “celebrating small things” we will be sharing plenty of information about NanoLuc® applications over the next few weeks, and will also be highlighting other examples where “small” can be a beautiful thing. By definition, molecular biology is a study of the smallest building blocks of life, so it’s not hard to find an abundance of small things to talk about. We hope you will participate with us by commenting, liking or sharing posts, or by contributing your own ideas on little things that make a difference, or that just make you smile.

Here’s a list for starters—it includes examples from history and from last week where going smaller turned out to be both smarter and better for overcoming a variety of biological challenges. Continue reading