The Medicinal Chemistry Center (CQMED), headquartered at Campinas State University in Brazil, recently started a project in partnership with Promega to develop drugs that can be used against Leishmania. This genus of protozoans is the etiological agent of leishmaniasis, transmitted to humans by sandflies.
Leishmaniasis is classified as a neglected tropical disease that mainly affects poor communities. Symptoms include large skin sores and an enlarged spleen. The challenge in developing drugs to treat Leishmania is finding appropriate therapeutic targets. These targets are normally proteins whose inhibition leads to death of the parasite. In addition to pharmaceutical company Eurofarma, whose goal is to develop drugs for Leishmania, Promega was chosen to help solve this problem because of our NanoBRET™ Target Engagement (TE) assay*, a well-established technique for measuring protein interactions. In this assay, NanoLuc® luciferase is attached to the protein of interest, and a fluorescent NanoBRET™ tracer molecule is added to the cells. This produces a BRET signal. When a competing ligand is added, it will displace the tracer molecule, enabling quantification of the strength of the interaction compared to the tracer molecule..
A challenge that researchers will face will be ensuring that the NanoBRET™ tracer reaches the inside of the parasite cells; because Leishmania is an intracellular parasite, molecules need to cross the host cell membrane, the membrane of the vacuole containing the parasites, and the membrane of the parasite itself. Another challenge the slow reproduction of Leishmania within macrophages. On top of that is the fact that the parasite’s metabolism varies depending on its biological cycle, meaning that there could be long periods of time during which a drug’s therapeutic target is not expressed in the cell, during which time the drug would have no effect. The ideal target would be expressed at high levels throughout the cell cycle.
The project is being led by Rafael Couñago, a researcher at CQMED, and Promega scientists Matt Robers and Jean-Luc Vaillaud.
*An earlier version of this blog incorrectly said that these experiments are based on the NanoBRET™ assay using HaloTag® protein.
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.
G Protein-Coupled Receptors (GPCRs) are a very large, diverse family of transmembrane receptors in eukaryotes. These receptors detect molecules outside the cell and activate internal signaling pathways by coupling with G proteins. Once a GPCR is activated, β-arrestins translocate to the cell membrane and bind to the occupied receptor, uncoupling it from G proteins and promoting its internalization.
Reporter tags are useful for studying the dynamics of GPCRs and associated proteins, but large tags can disrupt the receptors’ native functioning, and often overexpression of the tagged protein is required to obtain sufficient signal. Here is one example of how researchers have used the small, bright NanoLuc® luciferase to overcome these common challenges and answer questions about GPCRs. Continue reading “Lighting Up GPCR Research with Bioluminescent Tagging”
It’s a question I’m asked probably once a week. “What wavelength do I select on my luminometer when performing a luciferase assay?” The question is a good and not altogether unexpected one, especially for those new to bioluminescent assays. The answer is that in most cases, you don’t and in fact shouldn’t select a wavelength (the exception to this rule is if you’re measuring light emitted in two simultaneous luciferase reactions). To understand why requires a bit of an explanation of absorbance, fluorescence, and luminescence assays, and the differences among them.
Absorbance, fluorescence, and luminescence assays are all means to quantify something of interest, be that a genetic reporter, cell viability, cytotoxicity, apoptosis, or other markers. In principle, they are all similar. For example, a genetic reporter assay is an indicator of gene expression. The promoter of a gene of interest can be cloned upstream of a reporter such as β-galactosidase, GFP, or firefly luciferase. The amount of each of these reporters that is transcribed into mRNA and translated into protein by the cell is indicative of the endogenous expression of the gene of interest. Continue reading “Why You Don’t Need to Select a Wavelength for a Luciferase Assay”
Autism Spectrum Disorder, or ASD, is nothing if not unique.
The way ASD manifests itself in people is unique; although it most often presents as some form of variable impairment in social interaction and communication, each individual has behaviors and habits that are as unique to them as snowflakes are to one another.
ASD has also proven itself to be a uniquely challenging disorder to study. In the past decade, de novo (new) mutations have been identified as key contributors to causality of ASD. However, the majority of these identified de novo mutations are located in protein-coding genes, which comprise only 1–2% of the entire human genome.
Up to this point, a majority of previous research has focused on identifying mutations located in the 20,000 identified genes in the protein-coding region, which would seem like a promising approach. Genes are the genetic blueprints for creating proteins, which control and perform crucial tasks in our bodies, such as fighting off infections, communicating between your organs, tissues, and cells as chemical messengers, and regulating your blood sugar levels. It seems like basic math: Genes + Mutations = Mutated Proteins. Mutated Proteins = Disrupted Protein Function.
No protein is an island. Within a cell, protein-protein interactions (PPIs) are involved in highly regulated and specific pathways that control gene expression and cell signaling. The disruption of PPIs can lead to a variety of disease states, including cancer.
Two general approaches are commonly used to study PPIs. Real-time assays measure PPI activity in live cells using fluorescent or luminescent tags. A second approach includes methods that measure a specific PPI “after the fact”; popular examples include a reporter system, such as the classic yeast two-hybrid system.
The stage is set. You’ve spent days setting up this experiment. Your bench is spotless. All the materials you need to finally collect data are laid neatly before you. You fetch your cells from the incubator, add your detection reagents, and carefully slide the assay plate into the luminometer. It whirs and buzzes, and data begin to appear on the computer screen. But wait!
Don’t let this dramatic person be you. Here are 8 tips from us on things to watch out for before you start your next luminescent assay. Make sure you’ll be getting good data before wasting precious sample!
Malaria affects nearly half of the world’s population, with almost 80% of cases in sub-Saharan Africa and India. While there have been many strides in education and prevention campaigns over the last 30 years, there were over 200 million cases documented in 2017 with over 400,000 deaths, and the majority were young children. Despite being preventable and treatable, malaria continues to thrive in areas that are high risk for transmission. Recently, clinicians started rolling out use of the first approved vaccine, though clinical trials showed it is only about 30% effective. Meanwhile, researchers must continue to focus on innovative efforts to improve diagnostics, treatment and prevention to reduce the burden in these areas.
The storms of the previous day had moved eastward, leaving in their wake flooded farm fields and saturated roadside wetlands. At dusk, we loaded the Ford Escort wagon and headed south. We bumped along the maze of farm roads intent upon listening for croaks and snores in the night. At one roadside wetland, I heard my first congress of Spadefoot toads. The sound was deafening, invoking everything that a “congress of snoring toads” brings to mind. Around the corner, in a low spot of a corn field, a lone Spadefoot toad called for a mate; he was joined by a rather enthusiastic Copes Gray tree frog and several chorus frogs. The congress down the road provided a rolling bass to these more melodic anurans.
Wetlands exist in many different shapes and sizes and in many different geographies: coastal margins, mountain valleys, beaches and rocky shores, estuarine wetlands where tidal saltwater and freshwater mix, and inland wetlands. Some of them are ephemeral, some of them permanent. Wetlands serve many different functions, from providing habitat and food for plants and animals to offering protection from floods and maintaining water quality. One acre of one-foot deep wetland is estimated to hold 330,000 gallons of water. Coastal wetlands are important for reducing storm erosion by decreasing tidal surge and buffering the wind. In the US alone, this benefit has an estimated value of $23.2 billion dollars each year. Continue reading “Wetlands, Water Quality and Rapid Assays”
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”