UW hosts Nobel-winning research involving jellyfish protein

Osamu Shimomura would drift in a rowboat under the summer sky, meditating in the quiet waters near Friday Harbor in the San Juan Islands. Ferries would give him wide berth while he sat deep in scientific thought, wondering how to extract a bioluminescent protein from the jellyfish that were abundant in the harbor. The answer came suddenly one afternoon in 1961, and Shimomura rowed quickly back to the UW’s Friday Harbor Laboratories to test his hypothesis. His epiphany won Shimomura the 2008 Nobel Prize in chemistry.

The prize was awarded on Oct. 8 to Shimomura, along with two other scientists, Martin Chalfie and Roger Tsien. Shimomura is no longer associated with the UW and now works out of Wood Holes, Mass. However, the majority of his work with jellyfish was done during summers between 1961 and 1988 at the UW’s Friday Harbor labs. During this time, it is estimated Shimomura collected about one million specimens of jellyfish.

Shimomura was in Friday Harbor studying photoproteins in a species of jellyfish called Aequorea victoria. These animals bioluminesce, producing blue light from the ring around their outside. An enzyme Shimomura named “aequorin” causes this bioluminescence. This research led to the Nobel Prize-winning discovery of an important protein called green fluorescent protein (GFP). GFP is transduced from the reaction between aequorin and calcium found in seawater.

This protein is used as a marker, or signifier, that a cell has adopted the protein to which the GFP is attached. It can be used to track cancer cells in the body, show how the HIV virus spreads and even make rabbits glow green.

“Shimomura was first really excited by aequorin,” said Dennis Willows, a graduate student during Shimomura’s initial discoveries and, later, director of the labs where Shimomura furthered his research. “This then transferred to his work with GFP ... Like all great discoveries, the uses of something aren’t always obvious at first.”

However, the road to a Nobel Prize wasn’t easy. While floating in his rowboat, Shimomura was trying to figure out how to remove the protein that caused the bioluminescence. Traditional methods used in other jellyfish, such as deactivating an enzyme called luciferase, had proven fruitless.

“A thought suddenly struck me,” Shimomura reflected in a paper published in 1995. “A thought so simple that I should have had it much sooner.”

Shimomura realized that another enzyme or protein must be involved in the production of the Aequorea glow.

He hypothesized that he could deactivate the enzyme, allowing for aequorin’s extraction by changing its pH. Back at the labs, the hypothesis proved to be correct, and Shimomura was able to isolate aequorin. The real discovery, however, came later.

“I added a small amount of seawater to the solution and saw that its light became explosively strong,” he wrote. “Because the composition of seawater is known, I quickly discovered that the activator is Ca2+ [calcium].”

Willows said this discovery delighted many scientists who were working on nerve excitation. Calcium is an important part of nerve firing and Shimomura’s newly discovered aequorin would light up in proportion to the amount of calcium present. Willows said it was important for his research on excitable muscle and nerve cells.

It wasn’t all smooth sailing to the Nobel Prize for Shimomura. Aequorin wasn’t cloned until 1985, and it took 50,000 jellyfish to produce 150-200 milligrams of the purified protein. While this was enough to conduct a single experiment ­— Shimomura collected jellyfish over the summer at Friday Harbor and conducted experiments during the winter in Princeton — it would require that about 3,000 jellyfish be collected and processed every day. Jellyfish were plentiful at the time, with some accounts that a person could almost walk across them, but Shimomura could only collect about 1,000 a day during the early 1960s. He hired local kids to catch Aequorea at a rate of one cent per jellyfish.

“Even my kids were involved in collecting the jellyfish,” Willows said.

Processing the jellyfish took a considerable amount of time as well. Originally, Shimomura and his team would cut the ring at the edge of each jellyfish — where the glow proteins are located — by hand with scissors.

“They developed what was called the guillotine,” said Claudia Mills, an expert on jellyfish who works at the Friday Harbor labs. “It had a hole in the middle that water would flow through and would spread the jellyfish out. They would slowly spin the jellyfish through a razor blade, cutting off the ring.”

These innovations allowed Shimomura to collect 3,000 to 4,000 jellyfish a day, and he continued to do so throughout the 1960s and 1970s.

During this time, Aequorea remained plentiful, but something changed, and the stock started to decline.

“We thought at first it was a bad year,” Mills said. “They are just no longer in the water and we don’t know why. But this is natural and new species disappear every year and new species come.”

Mills added that the jellyfish’s decline was not caused by Shimomura’s intense collection of them. There were around 75 other species of jellyfish in the San Juan Islands when Shimomura was studying, but he was only interested in Aequorea. All species of jellyfish have since declined in numbers.

Aequorin is now synthetically produced and no longer relies on extraction from jellyfish. The GFP protein that won Shimomura the Nobel Prize has been cloned as well.

GFP works together with aequorin to produce the jellyfish’s glow. It, however, glows green and is useful because it doesn’t require any other component to glow besides ultraviolet light. Shimomura didn’t realize its importance at first and focused his research on aequorin. It was Chalfie and Tsien, who shared the prize with Shimomura, who understood GFP’s potential as a genetic marker protein, meaning it could be inserted into cells or entire organisms.

Today, GFP is an important tool in the biological and medical sciences, and it is used at the Friday Harbor lab’s Center for Cell Dynamics, as well as around the world.

“Shimomura was a very smart, curious and hard-working man,” Willows said. “But over time the University support comes and goes, resources become less accessible. It is possible that if the labs hadn’t been supported by the UW that Shimomura wouldn’t have done his work and GFP would not have been discovered.”

Reach reporter Nikolaj Lasbo at features@dailyuw.com.