Toxoplasma-induced autophagy: a window into nutritional futile cycles in mammalian cells?

The regulation and function of autophagy in response to metabolic signals is not yet well understood. A recent study from our laboratory indicates that an intracellular parasite, Toxoplasma gondii, derives nutritive benefit from the upregulation of host cell autophagy. We discuss this and related findings suggesting that autophagy in infected cells functions as part of a metabolic futile cycle. The hypothesis is presented that endogenous autophagy-based futile cycles may operate in normal mammalian cells, providing a substrate for manipulation by pathogens.