Cells give up their secrets slowly. Just when you think that all major cellular systems are understood, along comes a surprise. The latest is about autophagy, a major pathway for degrading and recycling within cells.
The name comes from Greek words meaning “self” and “eating”, and was coined to describe how a cell facing starvation degrades its own components, especially proteins, to obtain nutrients for survival. Autophagy also helps in the normal ‘turnover’ of cellular constituents and organelles. New findings show that autophagy has pivotal roles not only in development and cell death, but also provides an innate ‘second line of defense’ against invading pathogens.
In work just published in Science, the laboratory of Tamotsu Yoshimori at Japan’s National Institute of Genetics in Mishima and Ichiro Nakagawa and co-workers at Osaka University Graduate School of Dentistry report a new major role for autophagy—the elimination of invading pathogenic bacteria within cells. Autophagy involves the formation of unique double membrane structures called autophagosomes that can envelop portions of the cytoplasm and organelles. Eventually, autophagosomes fuse with lysosomes, enzyme- and acid-filled bags inside cells, to degrade their contents. Yoshimori and colleagues say that autophagosomes are used to capture invading bacteria that break through the cell’s primary defenses.