Illuminating the Function of a Dark Kinase (DCLK1) with a Selective Chemical Probe

The understudied kinome represents a major challenge as well as an exciting opportunity in drug discovery. A team of researchers lead by Nathanael Gray at the Dana Farber Cancer Institute was able to partially elucidate the function of an understudied kinase, Doublecortin-like kinase 1 (DCLK1), in pancreatic ductal adenocarcinoma cells (PDAC). The characterization of DCLK1 in PDAC was realized by developing a highly specific chemical probe (1). Promega NanoBRET™ Target Engagement (TE) technology enabled intracellular characterization of this chemical probe.

The Dark Kinome

NanoBRET target engagement

Comprised of over 500 proteins, the human kinome is among the broadest class of enzymes in humans and is rife with targets for small molecule therapeutics. Indeed, to date, over 50 small molecule kinase inhibitors have achieved FDA approval for use in treating cancer and inflammatory diseases, with nearly 200 kinase inhibitors in various stages of clinical evaluation (2). Moreover, broad genomic screening efforts have implicated the involvement of a large fraction of kinases in human pathologies (3). Despite such advancements, our knowledge of the kinome is limited to only a fraction of its family members (3,4). For example, currently less than 20% of human kinases are being targeted with drugs in clinical trials. Moreover, only a subset of kinases historically has garnered substantial citations in academic research journals (4). As a result, a large proportion of the human kinome lacks functional annotation; as such, these understudied or “dark” kinases remain elusive to therapeutic intervention (4).

Continue reading “Illuminating the Function of a Dark Kinase (DCLK1) with a Selective Chemical Probe”

RiboMAX and the Effort to Find Antiviral Drugs to Fight Coronaviruses and Enteroviruses

Prior to 2020, there were two major outbreaks of coronaviruses. In 2003, an outbreak of SARS-CoV sickened 8098 people and killed 774. In 2012, an outbreak of MERS-CoV began which so far has sickened 2553 and killed 876. Although the overall number of MERS cases is low, the disease has a high fatality rate, and new cases are still being reported. Even though fatality rates are high for these two outbreaks, containment was quickly achieved. This makes development of a treatment not commercially viable so no one had undertaken a large effort to develop an approved treatment for either coronavirus infection.

Fast forward to late 2019/2020… well, you know what has happened. There is currently no reliable antiviral treatment for SARS-CoV-2, the coronavirus that causes COVID-19 infections.

Zhang, et al. thought of a way to make an antiviral treatment commercially viable. If the treatment is actually a broad-spectrum antiviral, it could be used to treat more than one infection, meaning, it can be used to treat more people and thus be seen as more valuable and worth the financial risk to pharmaceutical companies. So, they decided to look at the similarities between coronaviruses and enteroviruses.

Continue reading “RiboMAX and the Effort to Find Antiviral Drugs to Fight Coronaviruses and Enteroviruses”

CRISPR/Cas9 Knock-In Tagging: Simplifying the Study of Endogenous Biology

Understanding the expression, function and dynamics of proteins in their native environment is a fundamental goal that’s common to diverse aspects of molecular and cell biology. To study a protein, it must first be labeled—either directly or indirectly—with a “tag” that allows specific and sensitive detection.

Using a labeled antibody to the protein of interest is a common method to study native proteins. However, antibody-based assays, such as ELISAs and Western blots, are not suitable for use in live cells. These techniques are also limited by throughput and sensitivity. Further, suitable antibodies may not be available for the target protein of interest.

Continue reading “CRISPR/Cas9 Knock-In Tagging: Simplifying the Study of Endogenous Biology”

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”

How Do You Solve a Problem Like Malaria?

malaria_researcher
Photo courtesy of NIH/NIAID

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.

Continue reading “How Do You Solve a Problem Like Malaria?”

Quantitating Kinase-Inhibitor Interactions in Live Cells

Kinase target engagement is a new way to study kinase inhibitors for target selectivity, potency and residency. The NanoBRET™ TE Intracellular Kinase Assays enable you to quantitate kinase-inhibitor binding in live cells, making these assays an exciting new tool for kinase drug discovery research.

For today’s blog about NanoBRET™ TE Intracellular Kinase Assay, we feature spokesperson Dr. Matt Robers. Matt is part of Promega’s R & D department and is one of the developers of the NanoBRET™ TE Intracellular Kinase Assay. Continue reading “Quantitating Kinase-Inhibitor Interactions in Live Cells”

The Wide World of Bioprocessing: Science for the Greater Good

My former research career was spent in academic laboratories, and I don’t have first-hand experience in the world of bioprocessing. However in my current job as a science writer/copy editor, I create product information and literature about products that are useful to bioprocessing engineers and technicians, and thus wanted to learn more about this diverse area, where discovery and processing of biomaterials results in better therapeutic drugs, better biofuels and even healthier foods.

Bioprocessing is a combination of biological science and chemistry, and a burgeoning science field. Burgeoning is an understatement. Exploding is a much more apt description.

This 2011 Science magazine careers article defines bioprocessing thusly:

“Bioprocessing is an expanding field encompassing any process that uses living cells or their components (e.g., bacteria, enzymes, or chloroplasts) to obtain desired products, such as biofuels and therapeutics.”

Continue reading “The Wide World of Bioprocessing: Science for the Greater Good”

Increasing Drug Research and Development Efficiency Using a 4-point Screening Method to Determine Molecular Mechanism of Action

Fig 4. Four point MMOA screen for tideglusib and GW8510. Time dependent inhibition was evaluated by preincubation of TbGSK3β with 60 nM tideglusib and 6 nM GW-8510 with 10μM and 100μM ATP. (A). Tideglusib [60 nM] in 10μM ATP. (B). GW8510 [60 nM] in 10μM ATP. (C.) Tideglusib [60 nM] at 100μM ATP. (D.) GW8510 [60 nM] at 100μM ATP. All reactions preincubated or not preincubated with TbGSK3β for 30 min at room temperature. Experiments run with 10μM GSM peptide, 10μM ATP, and buffer. Minute preincubation (30 min) was preincubated with inhibitor, TbGSK3β, GSM peptide, and buffer. ATP was mixed to initiate reaction. No preincubation contained inhibitor, GSM peptide, ATP, and buffer. The reaction was initiated with TbGSK3β. Reactions were run at room temperature for 5 min and stopped at 80°C. ADP formed was measured by ADP-Glo kit. Values are mean +/- standard error. N = 3 for each experiment and experiments were run in duplicates. Control reactions contained DMSO and background was determined using a zero time incubation and subtracted from all reactions. Black = 30 min preincubation Grey = No preincubation.
Four point MMOA screen for tideglusib and GW8510.
Time dependent inhibition was evaluated by preincubation of TbGSK3β with 60 nM tideglusib and 6 nM GW-8510 with 10μM and 100μM ATP. (A). Tideglusib [60 nM] in 10μM ATP. (B). GW8510 [60 nM] in 10μM ATP. (C.) Tideglusib [60 nM] at 100μM ATP. (D.) GW8510 [60 nM] at 100μM ATP. All reactions preincubated or not preincubated with TbGSK3β for 30 min at room temperature.  Black = 30 min preincubation Grey = No preincubation.
The first small-molecule kinase inhibitor approved as a cancer therapeutic, imatinib mesylate (Gleevec® treatment), has been amazingly successful. However, a thorough understanding of its molecular mechanism of action (MMOA) was not truly obtained until more than ten years after the molecule had been identified.

Understanding the MMOA for a small-molecule inhibitor can play a major role in optimizing a drug’s development. The way a drug actually works–the kinetics of binding to the target molecule and how it competes with endogenous substrates of that target–ultimately determines whether or not a a candidate therapeutic can be useful in the clinic. Drugs that fail late in development are extremely costly.

Drug research and discovery for neglected tropical diseases suffer from a lack of a large commercial market to absorb the costs of late-stage drug development failures. It becomes very important to know as much as possible, simply and quickly, about MMOA for candidate molecules for these diseases that are devastating to large populations.

One such neglected topical disease is Human African trypanosomiasis (HAT, also known as sleeping sickness). Continue reading “Increasing Drug Research and Development Efficiency Using a 4-point Screening Method to Determine Molecular Mechanism of Action”

A New Way to Avoid False Hits During Compound Screening for Drug Discovery

One goal of drug discovery and research programs is to reduce false hits as early as possible in the process. Follow-up on false hits is costly in terms of time and resources, and the longer the false hits remain in the drug development pipeline, the more costly they are. So methods that can easily reduce the number of false hits during compound screening early in the discovery process are particularly sought after.

Reporter assays have proven to be invaluable tools for elucidating the mechanisms of action of small molecules or other agents on signaling pathways within cells, and the luciferase reporter assay has become a standard research tool in the biological research laboratory.

However, one caveat of using standard luciferase-based reporter assays for larger-scale compound screening efforts is the frequency of false hits that result from direct interaction of compounds with the luciferase reporter. This issue can be mitigated with a “coincidence reporter” system where two independent reporter proteins are produced from a single transcript. In this type of assay, a bicistronic transcript is stoichiometrically translated into two nonhomologous reporters by means of a 2A “ribosomal skipping” sequence. Since it is unlikely that compounds will interact with two distinct types of reporter, “coincident” responses will indicate on-target activity. Such a coincident reporter system provides an important control against costly false hits early in drug discovery research programs.

A paper published online in ACS Chem Biol in February describes the first successful application of the firefly/NanoLuc luciferase coincidence reporter system to identify new pathways that up-regulate PARK2 expression. Continue reading “A New Way to Avoid False Hits During Compound Screening for Drug Discovery”

Piecing the Puzzle Together: Using Multiple Assays to Better Understand What Is Happening with Your Cells

You often need several pieces of information to really understand what is happening within a cell or population of cells. If your cells are not proliferating, are they dying? Or, are you seeing cytostasis? If they are dying, what is the mechanism? Is it apoptosis or necrosis? If you are seeing apoptosis, what is the pathway: intrinsic or extrinsic?

If you are measuring expression of a reporter gene and you see a decrease in expression, is that decrease due to transfection inefficiencies, cytotoxicity, or true down regulation of your reporter gene?

To investigate these multiple parameters, you can run assays in parallel, but that requires more sample, and sample isn’t always abundant.

Multiplexing assays allows you to obtain information about multiple parameters or events (e.g., reporter gene expression and cell viability; caspase-3 activity and cell viability) from a single sample. Multiplexing saves sample, saves time and gives you a more complete picture of the biology that is happening with your experimental sample.

What information do you need about your cells to complete the picture?
What information do you need about your cells to complete the picture?

Multiplexing assay reagents to measure biomarkers in the same sample has often been considered an application only accomplished with antibodies or dyes and sophisticated detection instrumentation. However, Promega has developed microwell plate based assays for cells in culture that allow multiplexed detection of biomarkers in the same sample well using standard multimode multiwell plate readers. Continue reading “Piecing the Puzzle Together: Using Multiple Assays to Better Understand What Is Happening with Your Cells”