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Hiro Furukawa

Hiro Furukawa Photo courtesy of CSHL

By Daniel Dunaief

Following a relentless drive to succeed, scientists have a great deal in common with athletes.

In addition to putting in long hours and dedicating considerable energy to improving their results, these talented professionals also enjoy moments of success — large and small — as opportunities to appreciate the victories and then build to greater challenges.

And so it is for Hiro Furukawa, a Professor at Cold Spring Harbor Laboratory.

Hiro Furukawa. Photo courtesy of JMSA

Working with a team of scientists including at Emory University, Furukawa recently published a paper in the prestigious journal Nature in which he demonstrated the long-sought structural process that leads to the opening of an important channel in the brain, called the NMDAR receptor.

When this cellular channel doesn’t function correctly, it can lead to numerous diseases, including Alzheimer’s and depression. Understanding the structural details of this channel could, at some point in future research, lead to breakthrough treatments.

“Each moment of discovery is exciting and priceless,” Furukawa explained. “When I finally see what I have sought for many years — in this case, the mechanism of NMDAR channel opening — it fills me with immense euphoria, followed by a sense of satisfaction.”

That sounds like the kind of mountaintop moment that star athletes whose achievements people applaud share once they’ve reached a long-desire milestone, like, perhaps, winning a gold medal in the Olympics.

The thirst for more for Furukawa, as it is for those with a passion for success in other fields beyond science and athletics, is unquenchable and unrelenting.

“This feeling is fleeting,” he added. “Within a few hours, a flurry of new questions arising from the discovery begins to occupy my mind.”

Indeed, Furukawa suggested that he expects that many other scientists share this experience.

Forming a winning team

Furukawa and Stephen Traynelis, Professor and Director in the Department of Pharmacology and Chemical Biology at Emory University School of Medicine in Atlanta, started to work together on a series of modulators for the NMDAR protein about eight years ago.

Hiro Furukawa. Photo courtesy of JMSA

This particular protein binds to the neurotransmitter glutamate and to glycine, which is another compound. Once bound to both, the channel, as if responding to the correct combination in a garage door, opens, creating electrical signals that contribute to brain functions.

To study the way the binding of these molecules opened the channel, the researchers needed to figure out how to keep the receptor in the open position.

That’s where a combination of work in the labs of Traynelis and Dennis Liotta, also a Professor at Emory, came in. Liotta’s lab made over 400 analogs that Traynelis ran in his lab.

Liotta created a compound called EU-1622-A, which is now known as EU-1622-240, that upregulates NMDAR activity, Furukawa explained.

“We used cryo-EM [electron microscopy] to capture the NMDAR structure with the compound, validated its conformation through electrophysiology and elucidated the activation mechanism,” he said.

Incorporating EU-1622-240 along with glycine and glutamate into the GluN1-2B NMDAR sample, which is a specific subtype and is the easiest to work with, enabled a visualization of the open channel.

Furukawa described the compound Traynelis created at Emory as the “key factor in capturing the open channel conformation.”

Determining the structure of a functioning protein can provide clues about how to alter those that may be contributing to the onset or progression of a disease.

To be sure, Furukawa recognizes the work as one step in what’s likely to involve an extensive research journey.

“We still have a long way to go, but we’ve made progress,” Furukawa said. “In this study, a compound bound to NMDAR gave us a clue on how to control the frequency of ion channel openings. Both hyperactive and hypoactive functions of NMDAR ion channels have been implicated in Alzheimer’s disease, so being able to regulate NMDAR activity would be significant.”

Furukawa can’t say for sure if this compound could alleviate the symptoms of certain diseases, but it serves as a new series of potentially clinically relevant options to test.

The researchers are developing a method to purify NMDAR proteins from animal tissues. Once they accomplish that task, they should be able to isolate NMDAR from Alzheimer’s brains to compare them to a normally functioning protein.

Furukawa suggested that it’s probable that specific NMDAR conformations are stabilized to different extents in various diseases compared to normal brains.

The researchers have not yet presented this work at meetings. First author Tsung-Han Chou, who is a postdoctoral fellow in Furukawa’s lab, plans to present the work at upcoming conferences, such as the Biophysical Society Meeting.

The review process for the research proceeded quickly, as the team submitted the paper in February of this year. 

Next steps

As for what’s next, Furukawa suggested that the team planned to solidify their findings.

“We must determine if the channel opening mechanism applies to other types of NMDARs,” he said. “Although we observed that EU1622-A compound binds to NMDAR, its structure was not sufficient resolved.”

To facilitate the re-design of EU1622-240, the scientists will need to improve the cryo-EM map resolution.

Traynelis, meanwhile, said that he and Liotta are synthesizing new modulators in this class and related classes and are working on mechanisms of action for this series at all NMDA receptors as well as actions in neuronal systems.

“We have a robust synthetic program with our collaborator [Liotta], whose laboratory is synthesizing many new modulators in this class and related classes,” Traynelis explained.

Traynelis added that his goal is to “develop new medicines to address unmet clinical needs. We want to find new and effective therapeutic treatments that help patients.”

The Emory professor is excited about the “potential development of positive NMDA receptor allosteric modulators that could enhance NMDA receptor function.”

Broader perspective

Furukawa, who lives in Cold Spring Harbor and whose sons Ryoma, 16 and Rin, 13, attend senior and junior high school, respectively, was interested in international politics and economics when he attended Tufts University as an undergraduate.

These non-science topics provide additional perspective that enrich his life.

“I remain very interested in understanding history and the reasons behind current events in Europe, the Middle East, and the U.S.,” he said. “This endeavor is far more challenging than decoding NMDAR structures and functions.”

As for his collaborations, Furukawa suggested that the findings from this research inspire him to continue to search for more answers and greater scientific achievements.

“We will continue to unravel these mysteries in future studies,” Furukawa said. “The best is yet to come.”

When they work as they should, they become a part of a process that helps us remember the Amendments to the Constitution, the Pythagorean Theorem, or the words to a love poem by Elizabeth Barrett Browning. When they don’t work correctly, we can run into all kinds of problems, some of which can get worse over time.

The N-methyl-D-aspartate receptor, also known as the NMDA receptor, which has parts that are bound in the membrane of brain cells, or neurons, is at the center of learning and memory.

Up until last year, only parts of the NMDA receptors sticking out of the membrane were known. A lack of a three-dimensional understanding made it difficult to see how this receptor works. Hiro Furukawa, an associate professor at Cold Spring Harbor Laboratory, and his postdoctoral researcher, Erkan Karakas, provided considerably more structural details of this receptor.

“The structures of the full-length NMDA receptor that [Furukawa’s] lab generated last year are seminal,” said Lonnie Wollmuth, a professor in the Department of Neurobiology and Behavior at Stony Brook University and a collaborator with Furukawa on other work. “They are fundamental to understanding how the NMDA receptor operates and how it can be modified in the clinic.”

Wollmuth suggested Furukawa has an “outstanding” reputation and said the structure of the receptor will “drive the field in new directions.”

Furukawa cautioned that scientists are still missing a structural understanding of a piece of the receptor that protrudes into the cell. Seeing the structure of this receptor will “provide clues for developing new compounds and for redesigning existing compounds to minimize side effects associated with nonspecific targeting,” Furukawa explained.

When NMDA receptors open, sodium and calcium ions flow into the cells. Too much calcium in the cells can cause toxicity that results in the neurodegeneration observed in Alzheimer’s disease and injuries related to strokes. Changes in the concentration of these ions can excite the neuron and cause symptoms such as epilepsy.

Seeing the structure of this receptor can provide a road map to find places on it that can become too active or inactive. Researchers typically look for binding sites, where they can send in a drug that can affect the function of the receptor. The more binding pockets scientists like Furukawa find, the greater the opportunity to regulate the NMDA receptor function.

Furukawa’s lab includes two graduate students, four postdocs and a technician. He is collaborating with scientists at Emory University to design and synthesize novel compounds based on the protein structures. As he gets more research funding, Furukawa would like to add more expertise in bioinformatics, which involves using computer science and statistics to understand and interpret large collections of data.

Experts in this field can go through a database of compounds quickly, enabling scientists to conduct the equivalent of thousands of virtual experiments and screen out candidates that, for one reason or another, wouldn’t likely work.

Furukawa is also studying autoimmune disorders in which immune cells attack these important receptors. One of these diseases is called anti-NMDA receptor encephalitis. Susannah Cahalan wrote an autobiographical account of her struggle with the disease in a New York Times Best Selling Book called “Brain on Fire: My Month of Madness” in 2012.

Furukawa is collaborating with a group at the University of Pennsylvania to find a way to detect the autoimmune antibodies that causes encephalitis. He is working to find a way to quench autoimmune antibodies for an anti-NMDA receptor.

Furukawa lives in Cold Spring Harbor with his wife, Megumi, who used to be an elementary school teacher but is now taking care of their sons Ryoma, 7, and Rin, 4.

Furukawa, who moved from Japan to Boston in fifth grade, then back to Japan for junior high school and finished high school in Missouri, is enjoying an opportunity to grow his own vegetables on Long Island.

As an undergraduate at Tufts, Furukawa was more interested in international politics and economics than in science. When he took chemistry and physics classes, he said the work “clicked comfortably” and he wound up majoring in chemistry. As an eight-year-old, he recalled watching the stars at night through a telescope. When he saw a ring of Saturn for the first time, he was so excited that he couldn’t sleep.

Furukawa’s colleagues appreciate his dedication to his work.

“He is certainly driven,” said Wollmuth. “He is in an extremely competitive field, so he must work efficiently and hard.”