Autophagy: for better or for worse.

Autophagy is a lysosomal degradation pathway that degrades damaged or superfluous cell components into basic biomolecules, which are then recycled back into the cytosol. In this respect, autophagy drives a flow of biomolecules in a continuous degradation-regeneration cycle. Autophagy is generally considered a pro-survival mechanism protecting cells under stress or poor nutrient conditions. Current research clearly shows that autophagy fulfills numerous functions in vital biological processes. It is implicated in development, differentiation, innate and adaptive immunity, ageing and cell death. In addition, accumulating evidence demonstrates interesting links between autophagy and several human diseases and tumor development. Therefore, autophagy seems to be an important player in the life and death of cells and organisms. Despite the mounting knowledge about autophagy, the mechanisms through which the autophagic machinery regulates these diverse processes are not entirely understood. In this review, we give a comprehensive overview of the autophagic signaling pathway, its role in general cellular processes and its connection to cell death. In addition, we present a brief overview of the possible contribution of defective autophagic signaling to disease.