Above: Structure of an animal cell, including the lysosome (listed third on the right). Mariana Ruiz, Wikimedia Commons

If you were a cannibal, like the fictional character Hannibal, the thought of eating humans would make you smile, and maybe even drool! But chances are you’re not like Hannibal. And you probably find the idea of eating human organs rather creepy and repulsive.

But did you know that your body is already eating itself?

When parts of your cells are damaged or no longer useful, they get broken down and recycled. This process is called autophagy. It happens all the time, every day. And though it might sound gross, autophagy is actually your body’s way of making sure your cells are working properly.

Did you know? Autophagy comes from the Greek words auto ("self") and phagy ("to eat"). It literally means to eat oneself!

Recycling plants in your cells

In many ways, the process of autophagy is similar to what happens in a recycling plant. Think of how a pop can gets recycled. When you’re done drinking, the can goes in a recycling bin. Next, a recycling truck delivers it to the recycling plant. At the plant, the aluminum in the can gets broken down so it can be reused.

When part of a cell gets damaged or is simply no longer useful (like an empty pop can), your body targets it for removal and recycling. Autophagy separates the dysfunctional part of the cell into a bubble called a vesicle. It’s a bit like a recycling bin that protects the rest of the cell from damage.

Molecular motors act like recycling trucks, transporting the vesicles along microtubules, the cell’s road network. The vesicles get delivered to the lysosome, a recycling plant located inside every one of your body’s cells. There, the vesicles are mixed together in very strong acids, like in a metal recycling plant.

In the lysosome, the dysfunctional part of the cell in broken down into smaller units, just like the aluminum in a pop can gets broken down. These units are then released back into your body to be re-used.

You may already know that recycling materials like aluminum costs less than mining new raw materials. Similarly, your body uses less energy recycling parts of its cells that it would making new ones from scratch.

Did you know? Your body absorbs mitochondria, the power plants in your cells, when they stop producing energy. This process is called mitophagy.

Benefits for your body

Scientists first discovered autophagy in the early 1960s. However, they are only just beginning to discover the many ways it helps your body. For example, autophagy can help you conserve energy. If you were starving, your body would focus on recycling and reusing unnecessary or damaged cell parts. Then, once you were well-fed, autophagy would shut down so your body could convert the ingested food into energy.

Your body also triggers autophagy when your immune system detects a bacterial or viral threat. These intruders are quickly packaged up into vesicles for removal, before they have a chance to replicate and cause an infection. Finally, autophagy helps your body recover after strenuous exercise by removing damaged protein. This repair process is key to maintain skeletal muscle mass and function.

Too much of a good thing?

So, the more autophagy the better, right? Not exactly. The answer to this question is complex. Your body is constantly trying to achieve a state called homeostasis, or balance. And it is difficult for scientists to determine the perfect conditions for activating autophagy.

If your body experiences a lot of cellular stress and damage, then increased autophagy is a good thing. However, too much autophagy can cause your body to remove good cell parts along with the bad.

Too little autophagy can also be harmful. Think of what would happen if your body was overrun with damaged and unnecessary cell parts! In fact, research suggests that several neurodegenerative disorders, such as Alzheimer’s and Parkinson’s, are caused by an build-up of dysfunctional proteins in the brain. Scientists are studying how to activate autophagy and remove the damaged proteins.

The study of autophagy has progressed a lot in the past few decades. The field has grown so big that, in 2005, it got its own scientific journal, called Autophagy. Who knows what researchers will discover about autophagy next!

So the next time you feel hungry, just remember: everyone has a little bit of Hannibal inside of them—even you!

Learn More!

General information on autophagy:

The Discovery of Lysosomes and Autophagy (2010)
S. Castro-Obregon, Nature Education 3

Scientific articles related to autophagy:

The role of autophagy in neurodegenerative disease (2013)
R.A. Nixon, Nature Medicine 19

Exercise-induced BCL2-regulated autophagy is required for muscle glucose homeostasis (2012)
C. He et al., Nature 481

Mitophagy: mechanisms, pathophysiological roles, and analysis (2012)
W.-X. Ding & X.-M. Yin, Biological Chemistry 393

Autophagy in immunity and inflammation (2011)
B. Levine, N. Mizushima & H. W. Virgin, Nature 469

Caloric restriction and resveratrol promote longevity through the Sirtuin-1-dependent induction of autophagy (2010)
E. Morselli et al. Cell Death & Disease 1

Autophagy: process and function (2007)
N.Mizushima, Genes & Development 21

Autophagy in Health and Disease: A Double-Edged Sword (2004)
T. Shintani & D. J. Klionsky, Science 306

Chris Chen

Chris obtained a bachelor of science degree with honours and then a masters in Science from the University of Toronto. He just started his PhD degree in Kinesiology at York University and is currently studying mitochondrial function in aging and exercising muscle. In his spare time, he enjoys jogging, swimming and playing on his violin.

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