Why this Japanese scientist won a 2016 Nobel Prize in medicine for cell ‘self-eating’

Yoshinori Ohsumi, a Japanese cell biologist, has won the 2016 Nobel Prize for physiology or medicine for his discoveries on a process whereby cells essentially eat themselves. The process is called autophagy, and though it’s essential for your health, your high school biology teacher may have skipped a lesson on autophagy due to its complexity.

Think of autophagy as a cell’s internal spa or recycling plant. Cells use autophagy for self-renewal.

Yoshinori Ohsumi. Illustration by N. Elmehed. © Nobel Media 2016

When our cells are starved or otherwise stressed, they don’t immediately shut down. Instead, they employ autophagy to cannibalize their own components. The word autophagy (pronounced o-toff-a-gee) literally derives from the greek expression for self-eating, and this recycling process allows the cell to stay alive during tough times.

“By recycling part of the cellular content, autophagy allows our body to cope with starvation and with all types of stress,” said biologist Maria Masucci of the Nobel Assembly. “By capturing invading viruses and bacteria, autophagy is essential for the body’s defense against infection.”

Scientists first described autophagy in the 1960s, after discovering the cellular version of a garbage can, known as the lysosome. Parts of your cells are like parts of a car: they wear down with time. A lysosome is a spherical bubble that moves through a cell and collects these broken parts. Like a digestive system, the lysosome fills with acids and enzymes to disassemble these parts into their basic units — proteins, sugars and lipids — so they can be reused. Belgian scientist Christian de Duve won the 1974 Nobel Prize in physiology or medicine for the discovery of the lysosome.

Soon after spotting the lysosome, Duve and other researchers noticed another spherical trash can, except this one was larger and could consume huge portions of a cell. He called the process autophagy, but it was initially viewed as a one-off version of the lysosome, so only a handful of labs examined it over the next three decades.

Enter Yoshinori Ohsumi and baker’s yeast.

Our cells have different compartments. Lysosomes are akin to a cell’s garbage can. They contain enzymes for digestion of cellular contents. Yoshinori Ohsumi won the 2016 Nobel Prize in medicine for research on a similar compartment called the autophagosome. It engulfs larger portions of the cell, before fusing with the lysosome, where the contents are degraded into smaller constituents. This process provides the cell with nutrients and building blocks for renewal. Photo by the Nobel Assembly at the Karolinska Institutet

In the early 1990s, his lab created an experiment that involved starving baker’s yeast of nutrients. They noticed this stress caused the yeast cells to create these relatively huge, spherical trash cans — now known as autophagosomes. The structures were so big that the scientists could observe them with a regular light microscope, rather than a more time-consuming electron microscope.

This event was a major breakthrough, because it meant Ohsumi’s team could watch the creation and movements of autophagosomes in real-time.

Yoshinori Ohsumi, a professor of Tokyo Institute of Technology, attends a news conference after he won the Nobel medicine prize at Tokyo Institute of Technology in Tokyo, Japan, October 3, 2016. Photo by REUTERS/Kim Kyung-Hoon

This voyeurism became the key to understanding how autophagosomes and autophagy work. Ohsumi and his colleagues used chemicals to mutate individual genes in baker’s yeast to figure out what controlled autophagy. The team landed upon 15 crucial genes, published in 1992, which in essence launched a new branch of cell biology.

“When I started my work, every year, probably 20 papers appeared on autophagy,” said Ohsumi, who was in his lab when he learned about the news of his Nobel Prize. “Now it’s more than 5,000. It’s a huge change.”

His team also identified the first autophagy-related genes in mammals, which led others to examine the process in human disease. Too little autophagy is a common problem during old age. Diseases like Alzheimer’s and type 2 diabetes appear as our cells fail to clear out their gunk. On the flip side, too much autophagy can propel cancer or allow tumor cells to consume drugs.

Ohsumi, who currently works at the Tokyo Institute of Technology in Yokohama, becomes the 23rd Nobel Prize winner from Japan, and the country’s sixth medicine laureate. Of the 107 Nobel awards for physiology and medicine, Ohsumi becomes only the 39th to win as the sole recipient.