How cells know when it's time to eat themselves

Researchers at the University of California, San Diego School of Medicine, have identified a molecular mechanism regulating autophagy (mechanism that involves cell degradation of unnecessary or dysfunctional cellular components), a fundamental stress response used by cells to help ensure their survival in adverse conditions.

Senior author Kun-Liang Guan, PhD, a professor of pharmacology at UC San Diego Moores Cancer Center, and colleagues report in the 17 January issue of Cell that an enzyme called AMPK, typically involved in sensing and modulating energy use in cells, also regulates autophagic enzymes.

An electron microscope image of a mammalian cell with organelles depicted. In autophagy, some elements of a cell are degraded and recycled to generate nutrients and energy to sustain and preserve the whole cell.

Autophagy, which derives from the Greek words for ''self'' and ''eat,'' is triggered to protect cells when times are tough, such as when cells are starved for nutrients, infected or suffering from damaged organelles, such as ribosomes and mitochondria.

Much like the human body in freezing conditions will reduce operations in extremities to preserve core temperatures and organ functions, cellular autophagy involves the degradation and synthesis of some internal cellular elements to ensure survival of the whole.

The scientists found that AMPK regulates different complexes of an enzyme class called Vps34 kinase in different ways. Some Vps34 enzymes are involved in normal cellular vesicle trafficking – the vital movement of molecules inside a cell.