Nobels 2016: How Your Cells Stave Off Starvation

It's Nobel Prize Week 2016, which means it's basically science Christmas. And, as I'm standing here, we know the winner of the prize that arguably has the most to do with your body and how it works, the Nobel Prize in Physiology or Medicine. This year's prize has gone to cell biologist Yoshinori Osumi for his work on the phenomenon known as autophagy, the method that cells use to conserve nutrients to try to save themselves from dying. Osumi has received this honor because he discovered the genetic basis for this process in baker's yeast. Autophagy comes from the Greek for self-eating, and it's what a cell uses to recycle its worn-out proteins and organelles, especially when it's under stress. During autophagy, a cell transports its broken down components to a certain area where they can be taken apart so that their chemical compounds can be reused. Think of it like salvaging parts from a junkyard. The rusty old cars won't work anymore, but most of their parts are probably okay, so you can break them down, rebuild, and start over. Autophagy is something biologists have known about since the 1960s, but it wasn't until Osumi's landmark paper in 1993 that we started to understand how it actually works. First, Osumi needed a way to see autophagy in action, even though the parts being recycled are too small to see individually with a typical microscope. So he had to deactivate the part of the cell where this recycling was done, and watch all of the worn-out parts build up. In yeast, that's an organelle called a vacuole. So he modified some of the yeast genes that basically turned it off. That way, the cells used autophagy to send stuff to the vacuole, but instead of being broken down, it just piled up until the backlog became visible under the microscope. Then, Osumi altered different genes to figure out which ones were responsible for sending the old parts to the vacuole in the first place. This is the actual autophagy process. He reasoned that if the backlog of stuff didn't pile up in the vacuole, the genes that were supposed to send it there had to be the ones that had been turned off. He used this method to identify 15 genes that are crucial for autophagy. And this discovery provided the basis for studying the process in more complex organisms. Since then, we've learned that autophagy is essential for normal cellular function in all kinds of organisms, including humans. And problems in the autophagy process have been implicated in a wide range of human diseases, including diabetes and some forms of cancer. So researchers are now looking for treatments for these diseases that target autophagy, which wouldn't be possible without Osumi's work. We'll catch you up on the chemistry and physics prizes soon, but there's more news in the world of physiology. Specifically, the physiology of the teenage brain. Teenagers have a reputation for both taking risks and seeking rewards, and new research shows that both of these behaviors might be an evolutionary adaptation that helps make teens such excellent learners. Compared to adults, teenagers are more sensitive to rewards, and biologists have speculated that this helps us become independent by encouraging us to take more risks as we're getting ready to leave our families. But in a new study, psychologists from Harvard, UCLA, and Columbia University wanted to see how this drive for rewards affects how teens learn. So teenage and adult participants played a simple learning game while an MRI scanner read their brains. Through positive reinforcement and trial and error, participants learned to play the game. The reinforcement was simply the word correct or incorrect. But alongside that, players were also shown a picture of an unrelated object, like a birdhouse, that was completely incidental to the reinforcement. The results showed that, first, teens were better at the game than adults, suggesting that they're better at learning from reinforcement. But also, teens remembered the random objects that were associated with the reinforcement, especially the ones they guessed wrong. This suggested to researchers that their brains did a better job of retaining details when something unexpected happened. And what's more, the teens actually showed a different pattern of brain activation when they learned. In adults, a brain area called the striatum is known to handle the process of reinforcement. And when they played the game, it was mostly in the striatum that researchers saw activity. But the adolescents used both their striatum and another brain area, the hippocampus, which handles certain kinds of memory. And there was more communication between the striatum and the hippocampus in teens. This means the two brain areas were comparing notes back and forth, and that both reinforcement and memory were enhancing each other. Put together, all of this suggests that the teen brain is more inclined to seek rewards and better adapted to learn from them as a result. Thanks for joining us for this episode of SciShow News. Thanks to our sponsor, The Great Courses Plus, where you can get unlimited access to over 7,000 different video lectures taught by award-winning professors from the Ivy League and other top schools around the world. You can access courses about anything that interests you – science, literature, Nobel-appropriate subjects like physiology and medicine, like this course from Professor Dean Hodgkin called Physiology and Fitness. Right now, The Great Courses Plus is offering SciShow viewers a free one-month trial. 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