This blog was written by Sebastien Smick, Research Technician in Dr. Jacquin Niles’ laboratory at Massachusetts Institute of Technology (MIT)
Our lab is heavily focused on the basic biology and drug discovery of the human bloodborne pathogen Plasmodium falciparum, which causes malaria. We use the CRISPR/Cas9 system, paired with a TetR protein fused to a native translational repressor alongside a Renilla luciferase reporter gene, to conditionally knock down genes of interest to create modified parasites. We can then test all kinds of compounds as potential drug scaffolds against these gene-edited parasites. Our most recent endeavor, one made possible by Promega, is a medium-low throughput robotic screening pipeline which compares conditionally-activated or-repressed parasites against our dose-response drug libraries in a 384-well format. This process has been developed over the past few years and is a major upgrade for our lab in terms of data production. Our researchers are working very hard to generate new modified parasites to test. Our robots and plate readers rarely get a day’s rest!
Science is the practice of figuring out how things work and then using that knowledge to further our understanding or to create tools that can solve problems facing the world. Bioluminescent tools and assays are examples of science doing all these things. Bioluminescence is the light-yielding (luminescence) chemical reaction that is used by many lifeforms. When fireflies flicker in the twilight, they are using bioluminescence to flash on and off. Chemically, bioluminescence happens when an enzyme called luciferase acts on a light-emitting compound, luciferin, in the presence of adenosine triphosphate (ATP), magnesium and oxygen.
For scientists, bioluminescence can serve as a tool to help them understand many cellular functions. Since few animal or plant cells produce their own light, there is little to no background signal (light) to be concerned about. This lack of background means that all light coming from the sample can be measured. In fact, bioluminescence is often a preferred tool for scientists because it does not require an external light source or special filters, which are required for fluorescence-based technologies.
Promega scientists have developed bioluminescent tools and assays to support leading edge scientific research for decades, beginning in 1990 with the Luciferase biosensor technology based on firefly luciferase. Luciferase is a wonderful tool for studying how enzymes work because its output (light) is so easy to measure: samples are placed into a special instrument called a luminometer, and the amount of light being produced (Relative Light Units) is recorded. Bioluminescence technology can be configured to measure a variety of cellular biology, ranging from cell health to enzyme activity down to the specific event of turning a gene on or off. The advent of new techniques for genetic manipulation, along with an enhanced understanding of bioluminescence and the discovery and engineering of better luciferases, enables science to use bioluminescence in even more unique ways.
NAD is a pyridine nucleotide. It provides the oxidation and reduction power for generation of ATP by mitochondria. For many years it was believed that the primary function of NAD/NADH in cells was to harness and transfer energy from glucose, fatty and amino acids through pathways like glycolysis, beta-oxidation and the citric acid cycle.
Today, however, NAD is recognized as an important cell signaling molecule and substrate. The many regulatory pathways now known to use NAD+ in signaling include multiple aspects of cellular homeostasis, energy metabolism, lifespan regulation, apoptosis, DNA repair and telomere maintenance.
Before the COVID-19 global pandemic began, Dr. Xuping Xie, Assistant Professor of the University of Texas Medical Branch at Galveston, TX has been studying viruses, such as Dengue and Zika, for more than 10 years. Once the pandemic hit in early 2020, he was prepared to join the fight against the virus. “There was an urgent need to know: Is there a quicker way to develop therapeutics or antibodies to target SARS-CoV-2?” says Dr. Xie. “That’s why we immediately launched our SARS-CoV-2 project.”
His goal was to create an assay that could 1) screen for antiviral drugs and 2) quickly measure neutralizing antibody levels. The assay could be used to determine the immune status of previously infected individuals and to evaluate various vaccines under development. To achieve this, he wanted to create a reporter virus that is genetically stable and replicates similarly to the wild-type virus in cell culture.
Despite significant advancements in antimalarial drugs and widespread efforts to prevent transmission over the past decade, deaths from malaria remain high, particularly in younger children. New drugs with novel modes of action are urgently needed to continue reducing mortality and address drug resistance in the malaria parasite, Plasmodium falciparum. While tens of thousands of compounds have been identified as potential candidates through massive screening efforts, scalable methods for identifying the most effective compounds are needed.
Enter firefly luciferase, a dynamic reporter tool to investigate drug action. By creating transgenic P. falciparum that express the luc reporter gene, the researchers could monitor drug action over time. When the parasite is killed, it stops making the luciferase reporter. Since there is no new production of luciferase, levels fall quickly after the parasite dies, and a luciferase assay can determine how fast each drug killed the parasite.
Among the one trillion or so species that share space on our planet, complex relationships have emerged over time. Such relationships, in which two or more species closely interact, are collectively termed symbiosis. Although it’s commonly assumed that symbiotic relationships are mutually beneficial, this example constitutes only one type of symbiosis (known as mutualism). The traditional predator-prey relationship, clearly a one-sided arrangement, is also an example of symbiosis.
The sheer diversity of microbial species has led to the development of many well-characterized relationships with plants and animals. Perhaps the best-known example of mutualism in this context is the process of nitrogen fixation. In this process, various types of bacteria that live in water, soil or root nodules convert atmospheric nitrogen into forms that are readily used by plants. On the other hand, some types of bacteria-plant relationships are parasitic: the bacteria rely on the plant for survival but end up damaging their host. Parasitic relationships can have devastating ecological and economic consequences when they affect food crops.
Viruses are both fascinating and terrifying. Stealthy, insidious and often deadly, they turn our own cells against us. Over the past year, we have all had a firsthand view of what a new and unknown virus can do. The SARS-CoV-2 virus has caused a global pandemic, and left scientists and medical professionals scrambling to unravel its mysteries and find ways to stop it.
COVID-19 is considered a respiratory disease, but we know that the SARS-CoV-2 virus can affect other systems in the body including the vascular and central nervous systems. In fact, some of the most noted symptoms of SARS-CoV-2 infection, headache, and the loss of the sense of taste and smell, are neurological— not respiratory— symptoms.
Imagine you’re taking a refreshing night swim in the warm blue waters of Vieques in Puerto Rico. You splash into the surf and head out to some of the deeper waters of the bay, when what to your wondering eyes should appear, but blue streaks of light in water that once was clear. Do you need to get your eyes checked? Are you hallucinating? No! You’ve just happened upon a cluster of dinoflagellates, harmless bioluminescent microorganisms called plankton, that emit their glow when disturbed by movement. These dinoflagellates are known to inhabit waters throughout the world but are generally not present in large enough numbers to be noticed. There are only five ecosystems in the world where these special bioluminescent bays can be seen, and three of them are in Puerto Rico.
But you don’t have to travel to Puerto Rico or swim with plankton to see bioluminescence. There are bioluminescent organisms all over the world in many unexpected places. There are bioluminescent mushrooms, bioluminescent sea creatures—both large and small (squid, jellyfish, and shrimp, in addition to the dinoflagellates)—and bioluminescent insects, to name a few. Bioluminescence is simply the ability of living things to produce light.
Canine distemper virus (CDV) is a highly contagious pathogen that is the etiological agent responsible for canine distemper (CD), a systemic disease that affects a broad spectrum of both domestic dogs and wild carnivores. While there are commercially available vaccines for CDV that can provide immunity in vivo and protect canines from contracting CD, there is a strong demand for effective canine distemper antivirals to combat outbreaks. Such drugs remain unavailable to date, largely due to the laborious, time-consuming nature of methods traditionally used for high-throughput drug screening of anti-CDV drugs in vitro. In a recent study published in Frontiers in Veterinary Science, researchers demonstrated a new tool for rapid, high-throughput screening of anti-CDV drugs: a NanoLuc® luciferase-tagged CDV.
A recent article published in Cancers demonstrates a new method for targeting glial cells using a lentiviral packaging system that incorporated Zika virus envelope proteins. By using the reporter gene firefly luciferase, researchers demonstrated that a pseudotyped virus could infect cultured glioblastoma cells.
Viruses enjoy a fearsome reputation. SARS-CoV-2 is only the latest infectious agent that has garnered attention by becoming a worldwide pandemic. Even the viral name suggests that SARS-CoV-2 was not the first of its type [SARS-CoV is the virus behind the severe acute respiratory syndrome (SARS) that spread worldwide in the early 2000s]. There are many different families of viruses (e.g., coronavirus for SARS-CoV-2 or lentiviruses for HIV-1) and each show a preference to the cell types they want to infect. By investigating the life cycle of viruses to better understand their mechanisms, researchers can discover new opportunities that may be exploited.
In 2015 and 2016, the virus that concerned health authorities was Zika virus (ZIKV). While this virus generally caused mild disease, the babies of women who were infected during pregnancy were at increased risk for microcephaly and other brain defects. These defects were traced back to Zika virus infecting nerve tissue, specifically, glial cells. This discovery provided an opportunity to explore how Zika virus might affect the brain tumor, glioblastoma multiforme (GMB), especially the glioblastoma stem cells (GSCs) that resist conventional treatment and contribute to the poor prognosis for GMB. Studies suggested that Zika virus infection prolonged survival in animal glioma models and selectively killed GSC with minimal effects on normal cells. In fact, the molecules used by ZIKV to enter cells were predominantly found on tumors, not normal cells. Knowing that the ZIKV envelope proteins prM and E provide the target specificity for glial cells, Kretchmer et al. wanted to explore if ZIKV envelope proteins substituted in lentivirus packaging systems would be able to enter glioblastoma cells.
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