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Journal of Lipids
Volume 2011, Article ID 498768, 9 pages
http://dx.doi.org/10.1155/2011/498768
Review Article

PtdIns 3-Kinase Orchestrates Autophagosome Formation in Yeast

1Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12 jo Nishi-6 chome, Kitaku, Sapporo 060-0812, Japan
2Integrated Research Institute, Tokyo Institute of Technology, 4259-S2-12 Nagatsuda-cho, Midoriku, Yokohama 226-8503, Japan

Received 29 October 2010; Accepted 4 December 2010

Academic Editor: Xian-Cheng Jiang

Copyright © 2011 Keisuke Obara and Yoshinori Ohsumi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Eukaryotic cells can massively transport their own cytoplasmic contents into a lytic compartment, the vacuole/lysosome, for recycling through a conserved system called autophagy. The key process in autophagy is the sequestration of cytoplasmic contents within a double-membrane structure, the autophagosome. Autophagosome formation requires the elaborate cooperation of Atg (autophagy-related) proteins and lipid molecules. Phosphorylation of phosphatidylinositol (PtdIns) by a PtdIns 3-kinase, Vps34, is a key step in coordinating Atg proteins and lipid molecules. Vps34 forms two distinct protein complexes, only one of which is involved in generating autophagic membranes. Upon induction of autophagy, PtdIns(3)P, the enzymatic product of PtdIns 3-kinase, is massively transported into the lumen of the vacuole via autophagy. PtdIns(3)P is enriched on the inner membrane of the autophagosome. PtdIns(3)P recruits the Atg18−Atg2 complex and presumably other Atg proteins to autophagic membranes, thereby coordinating lipid molecules and Atg proteins.