Inhibitor of growth protein 4 interacts with Beclin 1 and represses autophagy.

Valentina Sica,Guillermo Mariño,Valentina Izzo,Mireia Niso-Santano,Guo Chen,Maria Chiara Maiuri,Sylvie Lachkar,José Manuel Bravo-San Pedro,Guido Kroemer

doi:10.18632/oncotarget.19033

Valentina Sica, Guillermo Mariño + Show 7 more

Open Access

https://doi.org/10.18632/oncotarget.19033

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Journal: Oncotarget	Publication Date: Jul 6, 2017
Citations: 4	License type: cc-by

Affiliation: Inserm, Sorbonne Paris Cité

Abstract

Beclin 1 (BECN1) is a multifunctional protein that activates the pro-autophagic class III phosphatidylinositol 3-kinase (PIK3C3, best known as VPS34), yet also interacts with multiple negative regulators. Here we report that BECN1 interacts with inhibitor of growth family member 4 (ING4), a tumor suppressor protein that is best known for its capacity to interact with the tumor suppressor protein p53 (TP53) and the acetyltransferase E1A binding protein p300 (EP300). Removal of TP53 or EP300 did not affect the BECN1/ING4 interaction, which however was lost upon culture of cells in autophagy-inducing, nutrient free conditions. Depletion of ING4 stimulated the enzymatic activity of PIK3C3, as visualized by means of a red fluorescent protein-tagged short peptide (FYVE) that specifically binds to phosphatidylinositol-3-phosphate (PI3P)-containing subcellular vesicles and enhanced autophagy, as indicated by an enhanced lipidation of microtubule-associated proteins 1A/1B light chain 3 beta (LC3B) and the redistribution of a green-fluorescent protein (GFP)-LC3B fusion protein to cytoplasmic puncta. The generation of GFP-LC3B puncta stimulated by ING4 depletion was reduced by simultaneous depletion, or pharmacological inhibition, of PIK3C3/VPS34. In conclusion, ING4 acts as a negative regulator of the lipid kinase activity of the BECN1 complex, and starvation-induced autophagy is accompanied by the dissociation of the ING4/BECN1 interaction.

Highlights

Macroautophagy, to which we refer as ‘autophagy’, is a catabolic process that cells use to cope with stressful conditions such as nutrient deprivation, organelle dysfunction or invasion of the cytoplasm by infectious pathogens [1, 2]
We investigated whether the interaction between Flag-inhibitor of growth family member 4 (ING4) and His-beclin 1 (BECN1) would depend on E1A binding protein p300 (EP300) or tumor suppressor protein p53 (TP53)
The results reported in this paper support the contention that ING4 is constitutively interacting with BECN1 in mammalian cells that are cultured in nutrient-rich conditions

Summary

Introduction

Macroautophagy, to which we refer as ‘autophagy’, is a catabolic process that cells use to cope with stressful conditions such as nutrient deprivation, organelle dysfunction or invasion of the cytoplasm by infectious pathogens [1, 2]. Autophagy consists in the sequestration of cytoplasmic material in doublemembraned vesicles (autophagosomes) that fuse with lysosome (autophagolysosomes) where the luminal content is degraded by the action of hydrolases operating at low pH [6]. The formation of autophagosomes is finely regulated by the concerted action of protein kinases, in particular unc-51 like autophagy activating kinases (ULK1/ ULK2), the beclin 1 (BECN1) lipid kinase complex and an ubiquitin-like conjugation system [7]. The first step of vesicles nucleation depends on the activation of phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3, best known as VPS34), which operates in the context of the BECN1 complex [8]. Numerous additional proteins interact with BECN1 to activate or inhibit VPS34 and to initiate or suppress autophagy [9,10,11,12]

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