Heterophagy

Heterophagy is a biological process involving the engulfment and degradation of extracellular material by a cell. This process is a crucial component of the lysosomal system, the cellular machinery responsible for breaking down waste products and cellular debris.

The mechanism of heterophagy begins with the formation of a phagosome, a vesicle that surrounds the material to be internalized. This phagosome then fuses with a lysosome, an organelle containing digestive enzymes. Inside the fused structure, known as a phagolysosome, the extracellular material is broken down into its constituent molecules.

Heterophagy plays several vital roles in cellular function. It is essential for nutrient acquisition in certain cell types, such as amoebas, where it allows for the uptake of external food particles. In multicellular organisms, heterophagy is a key mechanism for immune defense. Macrophages and neutrophils, for example, use heterophagy to engulf and eliminate pathogens like bacteria and viruses. This process also contributes to tissue homeostasis by removing damaged or aged cells and their components. Furthermore, heterophagy is involved in developmental processes, such as the remodeling of tissues. Dysregulation of heterophagy has been linked to various diseases, including inflammatory conditions and neurodegenerative disorders.