This process of internal house-cleaning in the cell is called autophagy literally self-eating and it is now considered the second form of programmed cell death (PCD). Apoptosis, the first kind of programmed cell death to be characterized, is now also known as Type I PCD.
Genes governing Type II PCD, autophagy, have been identified recently in many species, starting with baker's yeast, and some of the environmental triggers that start the process are being found. But there is still quite a bit of science to do before autophagy can be understood as either a good thing or a bad thing. The evidence points both ways.
"It's likely to be both, depending on when it happens," said Daniel Klionsky, a research professor at the University of Michigan Life Sciences Instituteand professor of molecular cellular and developmental biology and biological chemistry.
Klionsky, who has been studying autophagy in yeast, has written a review article on the latest work in the field with post-doctoral fellow Takahiro Shintani that is featured on the cover of the Nov. 5 edition of Science magazine. Klionsky also recently edited the authoritative book on autophagy.
A cell undergoing autophagy assembles tiny capsules called vesicles that surround and chew up parts of the cellular machinery from within. Autophagic vesicles have been seen in cells undergoing programmed cell death, but the evidence is not clear yet whether they're trying to protect the cell from apoptosis, or hastening its demise.
"Autophagy is the only way to get rid of damaged parts of the cell without trashing the whole thing. So in a nerve cell, for example, you'd want autophagy
Contact: Karl Leif Bates
University of Michigan