Fluorescent Ligands in Biological Research: Where We’ve Been, Where We’re Headed

Fluorescent tags (fluorophores), have become excellent tools for labeling cells and cellular components. They can be used for imaging large molecules like proteins, on down to cellular components and enzymes such as transcription factors. Once labeled, these molecules can be tracked in tissue or inside a cell, when the right tag is used.

What is the ‘right’ tag? It’s a tag with bright signal, with low background and good photostability. For small cell components like organelles, the tag must be cell-permeable and small enough to not interfere with normal cellular processes such as transcription and metabolism.

Significant advances have been made in fluorescent tags in the past two decades. Here we look at several papers noting these advances.

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Immunometabolism: The Dynamic Interplay of Cytokines and Metabolites

Immunometabolism is the study of how metabolic processes influence immune cell functions and how immune responses, in turn, shape cellular metabolism. This field examines the roles of cytokines and metabolites, which act as signaling molecules and energy sources, respectively. Cytokines can trigger or modulate metabolic pathways in immune cells, affecting their activation, growth, and response capabilities. Similarly, metabolites provide the necessary energy and building blocks that enable immune cells to proliferate, function optimally, and sustain their activity during immune responses. This dynamic interplay is crucial for maintaining health and combating disease. Together, cytokines and metabolites orchestrate a complex network that links metabolic health with immune competence on a systemic and cellular level. This blog discusses how cytokines and metabolites not only influence but also drive immune cell functions, revealing new avenues for therapeutic interventions across a range of diseases.

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Rethinking Cell Proliferation Assays

In the field of cancer research, accurately measuring cell proliferation is crucial for assessing the efficacy of therapeutic agents. This is particularly difficult with CDK 4/6 inhibitors, which arrest cells in the G1 phase without stopping their growth. This continued growth can skew results from proliferation assays which rely on factors that naturally scale with cell growth. These include mitochondrial activity (ATP levels), total cell protein, or mRNA as measured through the PRISM molecular barcoding strategy. Even though these cells are not dividing, the increase in these measurements can misleadingly suggest active proliferation.

There is growing awareness among researchers of these challenges.  A recent study highlights these limitations by demonstrating the discrepancies that arise when using metabolic assays to assess cell proliferation after treatment with drugs that induce cell cycle arrest. This blog post delves into the study’s implications and demonstrates how one of Promega’s latest developments is poised to address these challenges.

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Decoding the NAD+/NADH Ratio and Its Crucial Role in Cell Health

Nicotinamide adenine dinucleotide (NAD) exists in two forms in the cell: NAD+ (oxidized) and NADH (reduced). This molecule plays a pivotal role in metabolic processes, serving as a key electron carrier in the redox reactions that drive cellular metabolism. The balance between these two forms, commonly expressed as the NAD+/NADH ratio, is crucial for maintaining cellular function and the intracellular redox state. This article explores the significance of this ratio, how it impacts cellular processes, and the consequences of NAD+/NADH ratio dysregulation.

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Cancer Moonshot: Solving Tough Problems

At the American Association for Cancer Research meeting in April 2016, then Vice President of the United States, Joe Biden, revealed the Cancer Moonshot℠ initiative— a program with the goals of accelerating scientific discovery in cancer research, fostering greater collaboration among researchers, and improving the sharing of data (1,2). The Cancer Moonshot is part of the 21st Century Cures Act, which earmarked $1.8 billion for cancer-related initiatives over 7 years.  The National Cancer Institute (NCI) and the Cancer Moonshot program have supported over 70 programs and consortia, and more than 250 research projects.  According to the NCI, the initiative from 2017 to 2021 resulted in over 2,000 publications, 49 clinical trials and more than 30 patent filings. Additionally, the launch of trials.cancer.gov has made information about all cancer research trials accessible to anyone who needs it (3).

“We will build a future where the word ‘cancer’ loses its power.”

First Lady, Dr. Jill Biden

In February 2022, the Biden White House announced a plan to “supercharge the Cancer Moonshot as an essential effort of the Biden-Harris administration” (4).  Biden noted in his address that, in the 25 years following the Nixon administration’s enactment of the National Cancer Act in 1971, significant strides were made in understanding cancer. It is now recognized not as a single disease, but as a collection comprising over 200 distinct diseases. This period also saw the development of new therapies and enhancements in diagnosis. However, despite a reduction in the cancer death rate by more than 25% over the past 25 years, cancer continues to be the second leading cause of death in the United States [4].

The Cancer Moonshot is a holistic attempt to improve access to information, support and patient experiences, while fostering the development of new therapeutics and research approaches to studying cancer. In this article, we will focus on research, diagnostics and drug discovery developments.

Solving for Undruggable Targets

KRAS , a member of the RAS family, has long been described as “undruggable” in large part because it is a small protein with a smooth surface that does not present many places for small molecule drugs to bind. The KRAS protein acts like an off/on switch depending upon whether it has GDP or GTP bound.  KRAS mutations are associated with many cancers including colorectal cancer (CRC), non-small cell lung cancer (NSCLC), and pancreatic ductal adenocarcinoma (PDAC). The G12 position in the protein is the most commonly mutated; G12C accounts for 13% of the mutations at this site, and is the predominant substitution found in NSCLC, while G12D is prevalent in PDAC (5).

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The Central Dogma of Promega: The Story and Science Behind Our Kit Packaging Design

An amazing transformation is taking place, unseen and unnoticed, within the microscopic bits that make you, you.

A tightly coiled lattice unspools to reveal a sinuous DNA stand. Along its length, tendrils of RNA sprout, growing bit by genetic bit. Eventually, the signal to stop and break away arrives, yielding a new strand of RNA that faithfully transcribes the DNA strand’s genetic code. Proteins trim and splice this new growth, pruning it so it takes its final form, messenger RNA. More proteins then ferry this mRNA strand through a pore in the nuclear envelope into the open space of the cell’s cytoplasm. Ribosomes and codon-carrying tRNA alight onto the released mRNA strand, reading the instructions it has carried from the DNA in the nuclear nursery. From this trio new forms emerge, bulbous proteins shaped by their destined purpose.

And so it goes, every second of every day, in the tens of trillions of cells in your body…

…And on the tens of thousands of kit packages we deliver to customers across the globe every year.

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Connecting Synaptic Gene Polymorphisms to Parkinson’s Disease

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Neurodegenerative disorders represent a significant and growing concern in the realm of public health, particularly as global populations age. Among these, Parkinson’s disease (PD) stands out due to its increasing prevalence and profound impact on individuals. Characterized by the progressive degeneration of motor functions, PD is not just a health challenge but also poses substantial socio-economic burdens. While the etiology of Parkinson’s disease is far from simple, current research efforts elucidating its causes, mechanisms, and potential treatments illustrate the critical nature of this neurodegenerative disorder in today’s healthcare landscape.

In the clinic, Parkinson’s disease is often diagnosed as either sporadic or familial. Familial PD has a clear genetic basis, typically passed down through families, while sporadic PD, comprising about 90% of cases, occurs in individuals without a known family history of the disease. The exact cause of sporadic PD is not fully understood but is believed to be due to a combination of genetic predispositions and environmental factors. In contrast, the factors involved in familial PD are more thoroughly understood, offering insights into the molecular mechanisms underlying PD pathogenesis.

Polymorphisms and Parkinson’s Disease Susceptibility

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Expert Insights: A Look Forward at Multiplexing for in vivo Bioluminescence Imaging

Bioluminescent in vivo imaging tools

NanoLuc, NLuc

With advancements made over the past few decades, the future of in vivo bioluminescence imaging (BLI) continues to gain momentum. In vivo BLI provides a non-invasive way to image endogenous biological processes in whole animals. This provides an easier method to assess relevant systems and functions. Unlike fluorescent imaging, BLI relies on a combination of enzymes and substrates to produce light, greatly reducing background signal (Refaat et al., 2022). Traditional fluorescent tags are also quite large and may interfere with normal biological function. In vivo BLI research has been around for quite some time, primarily utilizing Firefly luciferase (Luc2/luciferin). A recent advancement was the creation of the small and bright NanoLuc® luciferase (NLuc). Promega offers an wide portfolio of NLuc products that provide ways to study genes, protein dynamics, and protein:protein interactions. To fully grasp the power of these tools, I interviewed several key investigators to determine their perspectives on the future of in vivo BLI. I was specifically interested in their thoughts on NLuc multiplexing potential with Firefly (FLuc), and future research areas. These two investigators are Dr. Thomas Kirkland, Sr. Scientific Investigator at Promega, and Dr. Laura Mezzanotte, Associate Professor at Erasmus MC.

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Dynein Motor Proteins Could Be the Moving Power Behind Cancer Metastasis

3D Cancer Cell

“The cancer has spread.” are perhaps some of the most frightening words for anyone touched by cancer. It means that cancer cells have migrated away from the primary tumor, invaded health tissues and firmed secondary tumors. Called metastasis, this event is the deadliest feature of any type of cancer (1). The cellular mechanisms that play a role in metastasis could serve as powerful therapeutic targets. Unfortunately, understanding of these mechanisms is limited. However, some studies have suggested a link between the dysregulation of microtubule motors and cancer progression. A new study by a team from Penn State has revealed that the motor protein dynein plays a pivotal role in the movement of metastatic breast cancer cells through two model systems simulating soft tissues (1).

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The Tiniest Test Tube: Studying Cell-Specific Protein Secretion

Free floating single cells, blue
Researchers explore an innovative method for single-cell analysis

Cells produce proteins that serve different purposes in maintaining human health. These bioactive secretions range from growth factors to antibodies to cytokines and vary between different types of cells. Even within a certain cell type, however, there are individual cells that produce more secretions than others, a phenomenon that especially interests scientists studying cell-based therapies. In contrast to molecular therapies, which typically involve specific genes or proteins, a primary challenge to crafting cell therapies is the wide range of functional outputs seen in cells that have the same genetic template. This leads to the question of what molecular properties, from a genomic and transcriptomic perspective, would lead one cell to produce more of a protein than its companions. 

There have been few investigative strategies put forth that allow scientists to connect a cell’s characteristics and genetic coding with its secretions. In July 2023 a team of scientists published a paper in Nature Communications outlining an innovative solution: little hydrogel particles, or “nanovials”, that essentially serve as tiny test tubes and can be used to measure protein secretion, track transcriptome data, and identify relevant surface markers in a single cell.

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