How to make a cell that takes out your trash
December 20, 2006
ANN ARBOR, Mich.--- If only we could coax our cells into being better housekeepers, vigilant about throwing out damaged or unneeded parts, our bodies would probably run a lot more smoothly.
Daniel Klionsky's lab at the University of Michigan Life Sciences Institute has come close to figuring out how specialized parts of cells make housekeeping their habit—work that may help scientists understand how to encourage cellular tidiness. The research is described in the cover article of the December 18 issue of the Journal of Cell Biology.
Klionsky's specialty is autophagy (literally "self-eating"), a process engaged in by spherical structures inside cells called vesicles, which take away degraded materials. Scientists have long appreciated the importance of these structures, also known as autophagosomes, but have not known how they are formed.
Klionsky, who is also a professor of molecular, cellular and developmental biology and a National Science Foundation Distinguished Teaching Scholar, found that two proteins previously not known to interact work together to bring membranes to a site in the cell where autophagosomes are assembled. Using yeast cells, Klionsky discovered that the proteins scavenge fragments of membranes to form new vesicles, which can then clean up the cell's debris.
In yeast, two types of the autophagy process exist. The first is bulk autophagy, which is caused by stress and starvation: a starved cell eats part of itself to survive in the same way that humans break down fat reserves when dieting or to survive starvation.
Klionsky, however, was looking for the second type—a specific path of self-eating that consumes only certain parts of the cell. His findings mean that scientists now can search for ways of targeting damaged organelles, misfolded proteins or even invading bacteria, all of which may underlie disease.
The paper "Recruitment of Atg9 to the preautophagosomal structure by Atg11 is essential for selective autophagy in budding yeast" by Congcong He, Hui Song, Tomohiro Yorimitsu, Iryna Monastyrska, Wei-Lien Yen, Julie E. Legakis, and Daniel J. Klionsky was the cover story of the December 18, 2006 issue of the Journal of Cell Biology.
Cover image: The cytoplasm to vacuole targeting (Cvt) pathway uses Atg11 to direct Atg9-containing membrane from mitochondria (top right) to forming autophagosomes (center) before eventual fusion with the vacuole (bottom right). Original painting by David S. Goodsell, based on the scientific design of Daniel J. Klionsky.
