extracellular ATP

#IAmScience: Sam Yanders

June 17, 2022 By Penquite, Cara (MU-Student) in #IAmScience Tags: extracellular ATP, FRIPS, plant science, undergraduate research

By Cara Penquite | Bond LSC

When Samantha Yanders stepped to the front of Monsanto Auditorium, she followed presentations from two researchers with three degrees each.

Yanders only had three years of undergraduate research experience.

Nevertheless, she pinned the microphone to her tie, ran her fingers through her short curly hair, and explained her research with a calm certainty to her voice.

Having just finished her junior year as a plant science undergraduate, Yanders spent the first week of her summer sharing her passion for plants with fellow researchers during the 2022 Interdisciplinary Plant Group Symposium.

“I want to be inclusive in how I talk about my work to be able to educate people,” Yanders said. “Even if you’re talking to molecular biologists, they may have no idea about extracellular ATP.”

A clear communicator and advanced undergraduate researcher, Yanders was selected to present her research in Monsanto Auditorium during the symposium and often helps write and edit manuscripts for her lab.

Yanders began research in the Gary Stacey lab through Freshman Research in Plant Science, a program that places plant science freshmen in MU labs. Yanders’ research focuses on the signaling role of extracellular ATP when a plant experiences high-salt conditions.

Within a cell, ATP is a molecule used for energy. However, research shows that when a plant is in high stress or damaging conditions, ATP outside the cell signals for protective mechanisms.

“It’s really clever because instead of spending energy to make both a signaling molecule and a signal receptor, it already has something that’s really high concentrations in the cell and very low concentrations outside the cell,” Yanders said. “So it’s easy for the plant. It just has to make a signal receptor.”

Under normal conditions there is less ATP outside the cell and a high concentration of ATP inside the cell since it is used as energy. However, under high salt conditions there is an increase in ATP outside the cell, which binds to receptors on the cell surface that communicate with the cell to stunt plant growth. Yanders’ work explores the impact of high salt environments for plants — an increasingly relevant project as climate change raises sea levels and increases salt deposits in soil.

Although she now enthusiastically recounts her work to auditoriums of fellow scientists, biology was not originally Yanders’ first choice.

“In high school, I knew that I wanted to do something scientific because I’ve always liked science,” Yanders said, “But I didn’t think I wanted to go into biology, because I saw biology as mainly oriented towards animals.”

Arabidopsis — Sam Yanders shows the roots of arabidopsis plants. Yanders studies extracellular ATP in arabidopsis and tobacco plants. Photo by Cara Penquite | Bond LSC

With her geneticist grandfather piquing her interest from a young age and her enthusiasm for environmental science in high school, once she learned Mizzou had a plant science program she was ready to commit.

“So I was like, ‘Okay, I’ll go into biology and focus on plants.’ And then I’m looking on the Mizzou website and they [have] plant science. I didn’t even know that was a thing,” Yanders said. “So I switched to plant science.”

After enjoying high school chemistry labs, Yanders was ready to take the next step into research labs as soon as possible. Freshman Research in Plant Science allowed Yanders the opportunity to join a lab right away — fostering her interest in plant research.

“As humans, we move around. We can adapt to change by moving and changing what we do,” Yanders said. “But a plant has to do all of that management from a stationary position. . . It can’t change the circumstances that it’s in, so it has to adjust itself to be able to adapt.”

Tobacco Plants — Tobacco plants grow under artificial light at Bond LSC. Photo by Cara Penquite | Bond LSC

Yanders’ love of plants extends beyond the walls of the lab, and she spends her free time in her herb garden where she learns more about plant and human interactions.

“The way that you interact with the plant fundamentally changes how the plant acts,” Yanders said. “So like with basil, if you just let a basil plant grow it just gets leggy and crazy, but if you do what you feel like is harming it by pinching the tops off, then it grows more compact and bushy, which is good for the plant.”

Yanders hopes to explore plant and human interactions in the future, potentially pursuing urban agriculture and ecology.

“I’m really interested in soil health, I feel like we’ve done a lot to deplete soils, and coming up with more renewable ways of doing things [and] producing things for human consumption,” Yanders said.

While uncertain which questions she will ask next, Yanders hopes to continue answering questions and explaining her research to others.

“[I like] being able to offer an explanation, and not just see it, but to create that explanation for other people,” Yanders said.

Learning From History

October 26, 2020 By Lauren Hines in Research Tags: extracellular ATP, plant signaling pathways

Sung-Hwan Cho, a research scientist in the Gary Stacey lab, checks in on the arabidopsis plants that he uses in his purinergic signaling experiments. | photo by Lauren Hines, Bond LSC.

By Lauren Hines | Bond LSC

Until the 1990s, the presence and significance of extracellular ATP, a nucleotide that normally provides energy to a cell, in animal cells was highly contested for decades. Now, the Gary Stacey lab at Bond Life Sciences Center is using that history lesson to explore ATP’s role in plant cells.

Let’s say you have $100 in your pocket. As you’re walking down the street, you throw dollar bills over your shoulder. Sounds ridiculous, right?

Much like these dollar bills, ATP is the currency of cells. When the idea of animal cells dispensing ATP outside the cell to trigger danger signals came out in the 1970s, the scientific community thought it was wasteful and therefore the idea was ridiculed.

“The idea of throwing money over your shoulder is a very good analogy because that’s a good way to influence people,” said Stacey, a principal investigator at Bond LSC. “Give them a financial incentive. It’s the same thing with ATP. The idea is that this is the currency of the cell, but they’re putting it outside the cell in order to signal and influence interactions with their environment or other cells.”

This process of ATP receptors on the cellular membrane bonding with molecules to send signals and communicate between cells is called purinergic signaling.

The term was coined by retired neurobiologist Geoffrey Burnstock in the 1970s when he discovered it in animals; however, Burnstock’s findings were met with skepticism. It wasn’t until 20 years later when the first ATP receptor in animal cells was discovered that his idea gained acceptance.

Today, animal cell purinergic signaling has been used to make drugs that target diseases and develop drug therapies. As for purinergic signaling in plant cells, the research is just beginning. Much like what Burnstock faced, this new research is met with skepticism.

“It was clear to me that if we really wanted to establish this so that people would believe it, we had to get the receptor,” Stacey said.

In 2014, the Stacey lab reported its first ATP receptor called P2K1. Earlier this year, they found another one called P2K2.

“I think more and more people are working on purinergic signaling in plants,” Stacey said. “I think we will see a big explosion of people working in this area. Just as is the case with the animal field, the plant field is really going to take off now that we actually know what the receptors are.”

Currently, the Stacey lab is trying to understand how these receptors work. Research scientist Sung-Hwan Cho from the Stacey lab took over the project regarding P2K1.

“The ATP study in animals is just half a piece of the puzzle,” Cho said. “You need to find the other half of the piece. For 40 years, many labs have already studied this, but in plants, there’s just been a few.”

Research done by the Stacey lab has shown that although not much is known about purinergic signaling in plants compared to in animals, purinergic signaling can impact plant growth, development, defense against diseases and stress tolerance. Cho is currently studying how P2K1 impacts certain metabolic pathways in plants.

In another experiment done by the lab, they found that mutants without the ATP receptor that experienced stress did not grow smaller while plants that did have the receptor and experienced stress grew smaller.

“That says the purinergic signaling is what’s mediating the stress response,” Stacey said. “That is affecting the development of the plant in response to stress… So, if we understand this better then maybe we can make plants that are more drought and stress-tolerant and grow better.”

Standing out through saliva

August 4, 2016 By Roger Meissen in Research Tags: Bond LSC, extracellular ATP, salivary glands, Sjogren's syndrome

Bond LSC scientist internationally recognized for work on salivary glands and autoimmune disorders

By Phillip Sitter | Bond LSC

You might not think too highly of spit, but you would quickly regret not having any.

People with Sjögren’s syndrome suffer chronic dry mouth and eyes from an overzealous immune system that attacks salivary and tear ducts, causing serious health issues.

Gary Weisman’s research might hold the key to understanding and managing this immune response, leading to effective treatment or even prevention of this ailment.

For this, the International Association of Dental Research, or IADR, awarded him the 2016 Distinguished Scientist Award for Salivary Research. Weisman accepted the award in June at the opening ceremonies of the IADR conference in Seoul, Republic of Korea.

Gary Weisman stands in his lab in Bond LSC where he studies the cellular mechanisms of auto-immune disease, specifically how the release of ATP from damaged cells signals receptors that trigger an immune response. | Phillip Sitter, Bond LSC

“We want the good, but not the bad,” said Weisman, a Bond Life Sciences Center investigator, of what we ideally want from our immune system’s functions.

Mice with un-checked autoimmune disease of their salivary glands have their glands destroyed. The disease can spread to other secretory organs next. An over-reactive immune system on a civil war-path can extend its damage to cause pancreatic failure and death.

The destruction wrought by Sjögren’s syndrome is self-inflicted, caused by an overreaction of our bodies’ defenses against infection and injury. This is what an autoimmune disease is.

But, our bodies’ immune cellular response team is complicated. Weisman said dozens of different cell types have been isolated and identified as part of the immune system, and he likens the immune system to fire, police and construction services in human society all working together.

While firefighters are meant to prevent further damage from an inferno, sometimes our bodies’ first responders start doing the equivalent of using dynamite to stop the spread of a fire.

In chronic inflammation, that autoimmune response can mean a burning, throbbing, constant pain. The key to a healthy immune response is balance. The balance has to be between containment and repair of damage caused by infection or injury and damage caused by chronic inflammation if that emergency response continues unabated.

Weisman has spent almost 30 years studying how to prevent our bodies’ immune system from over-reacting to threats and causing further harm.

Earlier in his career, Weisman studied how extracellular ATP plays a critical role in immune responses, and how too much of it can cause the over-reaction that leads to tissue destruction in autoimmune diseases. ATP, or adenosine 5’-triphosphate, is the main molecule used for energy in cellular activities inside cells. Weisman was one of the first scientists to study how damaged cells release ATP as a distress signal.

The released ATP signals receptors that “send out the alarm to the fire station” — the body’s immune cells, he said.

Once he understood this, Weisman began to manipulate the actions of released ATP to see how that would affect an immune response.

Mice with salivary gland autoimmune disease got healthy when the released ATP was prevented from activating their receptors on the surface of cells. Preventing the ATP receptors from being activated slowed down and even stopped the advance of autimmune disease.

Conversely, if you prevent the activation of the ATP receptors in lab mice with Alzheimer’s disease they die much more rapidly from the disease, Weisman said, suggesting that activation of immune cells by ATP is beneficial in slowing the progression of this disease.

Alzheimer’s disease and autoimmune diseases such as Sjögren’s syndrome are only some of the inflammatory diseases that Weisman has studied. With each of these diseases, the role of ATP receptors has to be investigated individually, suggesting that Weisman’s work may extend beyond salivary glands and the brain to other parts of the body.

“Our [ATP] receptor is also involved in heart disease,” Weisman said, and he added that other diseases like cystic fibrosis, cancer, lupus and arthritis have inflammatory components, too.

For now, we all fight a losing battle when it comes to our bodies’ management of the immune system. As we and our immune system age, it has the potential to destroy more than it protects and “eventually you could slip over to the dark side and die,” Weisman said.

In the meantime, Weisman said that a better understanding of the immune system could lead to more effective, targeted treatments of chronic inflammation and other autoimmune disorders. This could provide a new approach to control undesirable activation of the immune system beyond the use of with anti-histamines, anti-cytokines and ibuprofen.

Weisman is a Curator’s Distinguished Professor of Biochemistry. He began his salivary gland research at MU 27 years ago with Professor John Turner, before Turner’s retirement. Since then, his research has been continuously funded by the National Institutes of Health, where one of his recent grants was well scored and will likely be extended for another five years.

Bond LSC team identifies first plant receptor for extracellular ATP

January 16, 2014 By Roger Meissen in Research Tags: Arabidopsis, extracellular ATP

Jeongmin Choi (left), Gary Stacey (center) and postdoc Kiwamu Tanaka recently discovered the first plant receptor for extracellular ATP. — Jeongmin Choi (left), Gary Stacey (center) and Kiwamu Tanaka recently discovered the first plant receptor for extracellular ATP using Arabidopsis plants. *Roger Meissen/Bond LSC*

It’s the genetic equivalent to discovering a new sensory organ in plants.

A team at the University of Missouri Bond Life Sciences Center found a key gene that sniffs out extracellular ATP.

Scientists believe this is a vital way plants respond to dangers, such as insects chewing on its leaves. The journal Science published their research Jan. 17.

“Plants don’t have ears to hear, fingers to feel or eyes to see. They recognize these chemical signals as a way to tell themselves they are being preyed upon or there’s an environmental change that could be possibly detrimental, and they have ways to defend themselves,” said Gary Stacey, a Bond LSC biologist. “We have evidence that extracellular ATP is probably a central signal that controls the ability of plants to respond to a whole variety of stresses.”

ATP (adenosine triphosphate) is the main energy source inside any cell. All food converts to it before being used in a cell, and ATP is necessary to power many of the cell processes that create more energy. Its value as an energy reserve is squandered outside the cell.

Scientists spent years trying to figure out what this compound did while floating outside cell walls. Animal researchers found that answer in the 1990s. They identified the first ATP receptors, now seen to play roles in muscle control, neurotransmission, inflammation and development.

Plant scientists observe similar extracellular ATP responses in plant biochemistry, but until now could not identify the exact receptor for it or what it did.

“We call this new receptor P2K, and it’s unique to plants,” Stacey said. “Even though animals and plants hold some responses in common, they have evolved totally different mechanisms to recognize extracellular ATP.”

Led by Stacey, MU graduate student Jeongmin Choi and postdoc Kiwamu Tanaka screened 50,000 mutant Arabidopsis plants to find ones that didn’t respond to extracellular ATP. Using a protein called aequorin – which causes jellyfish to glow – the two-year process boiled down to whether a plant would produce light when ATP was added. Since aequorin only luminesces when it binds to calcium, those plants without extracellular ATP receptors stayed dark.

“If you add ATP to wild-type plants, calcium concentrations go up and the plants produce more blue light,” Choi said. “We found nine mutant plants with no increase in calcium and, therefore, no increase in light emission.”

These Arabidopsis plants contain aequorin. Aequorin produces blue light as a result of oxidation of the substrate, in a calcium-dependent manner. When wild-type seedlings were treated with 500 uM of ATP, intracellular calcium concentration is rapidly elevated. Increased calcium were bound to aequorin, which leads to blue light emission. Courtesy Jeongmin Choi

By comparing the genetic sequences of these nine mutants, Stacey’s lab pinpointed the gene to chromosome 5 and labeled it DORN 1, since it doesn’t respond to the nucleotide ATP.

This discovery casts a different light on previous research.

“What we think is happening is that when you wound a plant, ATP comes out in the wound and that ATP triggers gene expression, not the wounding in and of itself,” Stacey said. “We think ATP is central to this kind of wound response and probably plays a role in development, in a lot of other kinds of things.”

Future research will focus on exactly how this receptor works with ATP. Tanaka plans to study its protein structure, how it reacts to pests in lab situations and possible co-receptors that could also play a role in recognizing ATP.

Grants from the U.S. Department of Energy Office of Basic Energy Sciences and the Republic of Korea supported this research.