Atg13 Is Essential for Autophagy and Cardiac Development in Mice

Abstract

Autophagy is a major intracellular degradation system by which cytoplasmic components are enclosed by autophagosomes and delivered to lysosomes. Formation of the autophagosome requires a set of autophagy-related (Atg) proteins. Among these proteins, the ULK1 complex, which is composed of ULK1 (or ULK2), FIP200, Atg13, and Atg101, acts at an initial step. Previous studies showed that ULK1 and FIP200 also function in pathways other than autophagy. However, whether Atg13 and Atg101 act similarly to ULK1 and FIP200 remains unknown. In the present study, we generated Atg13 knockout mice. Like FIP200-deficient mice, Atg13-deficient mice die in utero, which is distinct from most other types of Atg-deficient mice. Atg13-deficient embryos show growth retardation and myocardial growth defects. In cultured fibroblasts, Atg13 deficiency blocks autophagosome formation at an upstream step. In addition, sensitivity to tumor necrosis factor alpha (TNF-α)-induced apoptosis is enhanced by deletion of Atg13 or FIP200, but not by other Atg proteins, as well as by simultaneous deletion of ULK1 and ULK2. These results suggest that Atg13 has both autophagic and nonautophagic functions and that the latter are essential for cardiac development and likely shared with FIP200 but not with ULK1/2.

View publisher note:

Article of Significant Interest Selected from This Issue by the Editors

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.01005-15.

ACKNOWLEDGMENTS

We thank Nao Hosokawa for the preparation of ES cells, Jun-Lin Guan for FIP200 KO MEFs, Masaaki Komatsu for Atg3 KO MEFs, Tatsuya Saitoh and Shizuo Akira for Atg9A, Atg14, and Atg16L1 KO MEFs, Sharon Tooze and Craig Thompson for ULK1/2 DKO MEFs, Toshio Kitamura and Shoji Yamaoka for retroviral vectors and Plat-E cells, Sumio Sugano for the pEF321-T plasmid, Akiko Kuma, Hideaki Morishita, and Keiko Igarashi for technical instruction, and Rieko Asai and Hiroki Kurihara for technical instruction and helpful discussion.

Additional information

Funding

This work was supported by the Funding Program for Next Generation World-Leading Researchers (LS043), JSPS KAKENHI grants-in-aid for scientific research on innovative areas (grant number 25111005 to Noboru Mizushima), and a grant-in-aid for JSPS fellows (grant number 23*4974 to Takeshi Kaizuka).