Differential Regulation of Distinct Vps34 Complexes by AMPK in Nutrient Stress and Autophagy

Abstract

Summary Autophagy is a stress response protecting cells from unfavorable conditions, such as nutrient starvation. The class III phosphatidylinositol-3 kinase, Vps34, forms multiple complexes and regulates both intracellular vesicle trafficking and autophagy induction. Here, we show that AMPK plays a key role in regulating different Vps34 complexes. AMPK inhibits the non-autophagy Vps34 complex by phosphorylating T163/S165 in Vps34, therefore suppresses overall PI(3)P production and protects cells from starvation. In parallel, AMPK activates the pro-autophagy Vps34 complex by phosphorylating S91/S94 in Beclin1 to induce autophagy. Atg14L, an autophagy essential gene present only in pro-autophagy Vps 34 complex, inhibits Vps34 phosphorylation but increases Beclin1 phosphorylation by AMPK. As such, Atg14L dictates the differential regulation (either inhibition or activation) of different Vps34 complexes in response to glucose starvation. Our study reveals an intricate molecular regulation of Vps34 complexes by AMPK in nutrient stress response and autophagy.

Antagonizing peroxisome proliferator‐activated receptor γ facilitates M1‐to‐M2 shift of microglia by enhancing autophagy via the LKB1–AMPK signaling pathway

“…As a regulator of autophagy (Kim et al., 2013; Mack, Zheng, Asara & Thomas, 2014; Shang & Wang, 2011), AMPK phosphorylation was found to be reduced in microglial cells after LPS exposure. Furthermore, the increase in AMPKα2 expression and reduction in p‐AMPK protein were restrained by the PPARγ antagonist T0070907 (Figure 3a,b).…”

Differential regulatory functions of three classes of phosphatidylinositol and phosphoinositide 3-kinases in autophagy

“…This dichotomous regulation is enabled by the preferential phosphorylation of free PIK3C3 (T163/S165) or BECN1 (S91/S94) in proautophagic class III PtdIns3K complexes by PRKA. 112 In addition to this selected modification under starvation, it is interesting that PIK3C3 activity is probably modulated in sync with cell cycle progression, supported by the evidence that CDK1 (cyclindependent kinase 1) and CDK5 phosphorylate PIK3C3 at distinct sites, which represses its activity. 113 Additionally, PRKD1/ PKD (protein kinase D1) phosphorylates PIK3C3 under conditions of oxidative stress, 114 and is dependent on acetylated HSPA1A (heat shock 70kDa protein 1A), whereas TRIM28/ KAP1 (tripartite motif containing 28) is able to mediate PIK3C3 SUMOylation in response to autophagy-inducing stress, 115 both of which activate autophagy.…”

“…It should be noted that the study by Russel et al 120 may offer a potential explanation: the opposing effects of amino acid withdrawal on class III PtdIns3K activity in PIK3C3-BECN1 and PIK3C3-ATG14 immunoprecipitates were demonstrated, and the presence of ATG14 is likely to determine the specific activation of the ATG14-containing PIK3C3 complex mediated by ULK1 phosphorylation of BECN1. Together with the evidence of differential regulation of PIK3C3 complexes by energy deprivation, 112 a hypothesis that may reconcile the contradictory roles of PIK3C3 in MTOR signaling and autophagy could be proposed: certain PIK3C3-interacting components, for instance ATG14, may specify the differential regulation of distinct PIK3C3 complexes by nutrients, or determine the spatial distribution of PIK3C3 that confers divergent biological functions. Alternatively, the requirement of PIK3C3 for MTORC1 activity may be ascribed to the release of amino acids by autophagic degradation.…”

“…111 As the core catalytic subunit in the class III PtdIns3K complex, PIK3C3 per se is a point of regulatory convergence by diverse autophagy-modulating mechanisms. A study by Kim et al 112 demonstrated the presence of 2 different regulatory mechanisms controlling the role of PIK3C3 in autophagy via: (i) formation of different protein complexes and (ii) direct phosphorylation of PIK3C3. In their study, PIK3C3 is present in 2 types of class III PtdIns3K complexes, nonautophagic and proautophagic; and glucose starvation selectively elevates the kinase activity of ATG14-or UVRAG-containing class III PtdIns3K complexes (proautophagic), but suppresses that of PIK3C3 in complexes lacking these 2 proteins (nonautophagic).…”

Extracellular stimulation of VSIG4/complement receptor Ig suppresses intracellular bacterial infection by inducing autophagy

“…BECN1/Beclin 1 is a key molecule needed for the formation of phagophores, the precursors to autophagosomes; 27 it is activated in the mouse when it dissociates from BCL2 and is phosphorylated at Ser91 and Ser94 sites. 28 Therefore, we asked whether VSIG4 triggering activates BECN1. Protein samples were prepared from LM-infected, RnIgG-or anti-MmVSIG4-treated J774 cells, and serum-starved cells.…”