MTORC1-mediated NRBF2 phosphorylation functions as a switch for the class III PtdIns3K and autophagy

Xi Ma; Shen Zhang; Long He; Yueguang Rong; Livia Wilz Brier; Qiming Sun; Rong Liu; Weiliang Fan; She Chen; Zhenyu Yue; Joungmok Kim; Kun-Liang Guan; Defa Li; Qing Zhong

doi:10.1080/15548627.2016.1269988

MTORC1-mediated NRBF2 phosphorylation functions as a switch for the class III PtdIns3K and autophagy

Autophagy. 2017 Mar 4;13(3):592-607. doi: 10.1080/15548627.2016.1269988. Epub 2017 Jan 6.

Authors

Xi Ma^{1

2

3}, Shen Zhang^{1

2

3}, Long He^{1

2

3}, Yueguang Rong^{2

3}, Livia Wilz Brier⁴, Qiming Sun⁴, Rong Liu^{2

3}, Weiliang Fan⁴, She Chen⁵, Zhenyu Yue⁶, Joungmok Kim⁷, Kun-Liang Guan⁷, Defa Li¹, Qing Zhong^{2

3}

Affiliations

¹ a State Key Lab of Animal Nutrition, Ministry of Agriculture Feed Industry Center , China Agricultural University , Beijing , China.
² b Center for Autophagy Research, Department of Internal Medicine , University of Texas Southwestern Medical Center , Dallas , TX , USA.
³ c Department of Biochemistry , University of Texas Southwestern Medical Center , Dallas , TX , USA.
⁴ d Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology , University of California , Berkeley , CA , USA.
⁵ e National Institute of Biological Sciences , Beijing , China.
⁶ f Department of Neurology and Neuroscience , Friedman Brain Institute, Icahn School of Medicine at Mount Sinai , New York , NY , USA.
⁷ g Department of Pharmacology and Moores Cancer Center , University of California , San Diego, La Jolla , CA , USA.

Abstract

NRBF2/Atg38 has been identified as the fifth subunit of the macroautophagic/autophagic class III phosphatidylinositol 3-kinase (PtdIns3K) complex, along with ATG14/Barkor, BECN1/Vps30, PIK3R4/p150/Vps15 and PIK3C3/Vps34. However, its functional mechanism and regulation are not fully understood. Here, we report that NRBF2 is a fine tuning regulator of PtdIns3K controlled by phosphorylation. Human NRBF2 is phosphorylated by MTORC1 at S113 and S120. Upon nutrient starvation or MTORC1 inhibition, NRBF2 phosphorylation is diminished. Phosphorylated NRBF2 preferentially interacts with PIK3C3/PIK3R4. Suppression of NRBF2 phosphorylation by MTORC1 inhibition alters its binding preference from PIK3C3/PIK3R4 to ATG14/BECN1, leading to increased autophagic PtdIns3K complex assembly, as well as enhancement of ULK1 protein complex association. Consequently, NRBF2 in its unphosphorylated form promotes PtdIns3K lipid kinase activity and autophagy flux, whereas its phosphorylated form blocks them. This study reveals NRBF2 as a critical molecular switch of PtdIns3K and autophagy activation, and its on/off state is precisely controlled by MTORC1 through phosphorylation.

Keywords: ATG14; BECN1; MTORC1; NRBF2; PI3KC3; PIK3C3; autophagy; phosphorylation.

MeSH terms

Amino Acid Sequence
Animals
Autophagy*
Autophagy-Related Protein-1 Homolog / metabolism
Autophagy-Related Proteins
Class III Phosphatidylinositol 3-Kinases / metabolism*
Mechanistic Target of Rapamycin Complex 1 / metabolism*
Mice
Phosphorylation
Phosphoserine / metabolism
Protein Binding
Stress, Physiological
Substrate Specificity
Trans-Activators / metabolism*
Transcription Factors / metabolism*

Substances

Autophagy-Related Proteins
NRBF2 protein, human
Nrbf2 protein, mouse
Trans-Activators
Transcription Factors
Phosphoserine
Class III Phosphatidylinositol 3-Kinases
Autophagy-Related Protein-1 Homolog
Mechanistic Target of Rapamycin Complex 1

Abstract

MeSH terms

Substances

Grants and funding