[Cellular defense by autophagy].

As an intracellular bulk degradation system, autophagy acts for the turnover of cellular constituents and in maintaining the amino acid pool by self degradation to survive starvation. A recent rapid expansion of the field triggered by identification of genes essential to autophagy has revealed its diverse functions other than catabolism. For example, autophagy can eliminate pathogenic bacteria invading host cells and the abnormal proteins causing neural or hepatic degenerative diseases. Therefore, autophagy is crucial for cellular defense against harmful materials inside cells.