What is an autophagolysosome?

An autophagolysosome is a particular type of small sac or vacuole that breaks down the junk in our cells during the process of autophagy.

Autophagy is the body’s self-cleaning process that clears out the damaged parts of our cells. It removes junk from our cells, including organelles that no longer work properly, misfolded proteins, aggregated macromolecules and disease-causing organisms, and degrades them.

There are three types of autophagy, but the term ‘autophagy’ is usually used to refer to the process of macroautophagy.

The process of macroautophagy starts when a portion of cytoplasm, the thick fluid inside the cell that surrounds the nucleus, is surrounded by a phagophore. A phagophore is an isolation membrane - a sack-like structure - that matures into an autophagosome.

Autophagosomes fuse with two vacuoles - endosomes and lysosomes - to enable the internal contents of the autophagosome to be broken down. It is the lysosomes that contain the enzymes that are able to break down and digest the contents of the autophagosomes.

When an autophagosome fuses with a lysosome an autolysosome or autophagolysosome is formed. Sometimes the term autolysosome and autophagolysosome are used interchangeably. However, a group of researchers have reported that the term autophagolysosome is more appropriate to use when a phagosome is involved in the autophagy process. For example, when a phagosome is contained within an autophagosome, the fusion product that is created when the autophagosome fuses with the lysosome is more appropriately called an autophagolysosome than an autolysosome.

Phagosomes are vesicles that play a role in the process of phagocytosis, which is a complementary process to autophagy that enables cells to capture and ingest other cells or foreign particles.