open access

https://hdl.handle.net/2115/45463

The Atg18-Atg2 Complex Is Recruited to Autophagic Membranes via Phosphatidylinositol 3-Phosphate and Exerts an Essential Function

英語

2008-08

American Society of Biochemistry and Molecular Biology

Journal of Biological Chemistry

283(35)

23972-23980

Atg18 is essential for both autophagy and the regulation of vacuolar morphology. The latter process is mediated by PtdIns(3,5)P2 binding, which is dispensable for autophagy. Atg18 also binds to PtdIns(3)P in vitro. Here, we investigate the relationship between PtdIns(3)P-binding of Atg18 and autophagy. Using an Atg18 variant, Atg18(FTTG), which is unable to bind phosphoinositides, we found that PtdIns(3)P-binding of Atg18 is essential for full activity in both selective and non-selective autophagy. Atg18(FTTG) formed a complex with Atg2 in a normal manner, and Atg18-Atg2 complex formation occurred in cells in the absence of PtdIns(3)P, indicating that Atg18-Atg2 complex formation is independent of PtdIns(3)P-binding of Atg18. Atg18 localized to endosomes, the vacuolar membrane, and autophagic membranes, while Atg18(FTTG) did not localize to these structures. The localization of Atg2 to autophagic membranes was also lost in Atg18(FTTG) cells. These data indicate that PtdIns(3)P-binding of Atg18 is involved in directing the Atg18-Atg2 complex to autophagic membranes. Connection of a 2xFYVE domain, a specific PtdIns(3)P-binding domain, to the C-terminus of Atg18(FTTG) restored the localization of Atg18-Atg2 to autophagic membranes and full autophagic activity, indicating that PtdIns(3)P-binding by Atg18 is dispensable for the function of Atg18-Atg2 complex but is required for its localization. This also suggests that PtdIns(3)P does not act allosterically on Atg18. Taken together, Atg18 forms a complex with Atg2 irrespective of PtdIns(3)P-binding, associates tightly to autophagic membranes by interacting with PtdIns(3)P, and plays an essential role.

学術雑誌論文

Accepted Manuscript

Copyright © 2008 the American Society for Biochemistry and Molecular Biology

0021-9258

1083-351X

AA1202441X