ULK1 phosphorylates Ser30 of BECN1 in association with ATG14 to stimulate autophagy induction

Abstract

ULK1 (unc51-like autophagy activating kinase 1) is a serine/threonine kinase that plays a key role in regulating macroautophagy/autophagy induction in response to amino acid starvation. Despite the recent progress in understanding ULK1 functions, the molecular mechanism by which ULK1 regulates the induction of autophagy remains elusive. In this study, we determined that ULK1 phosphorylates Ser30 of BECN1 (Beclin 1) in association with ATG14 (autophagy-related 14) but not with UVRAG (UV radiation resistance associated). The Ser30 phosphorylation was induced by deprivation of amino acids or treatments with Torin 1 or rapamycin, the conditions that inhibit MTORC1 (mechanistic target of rapamycin complex 1), and requires ATG13 and RB1CC1 (RB1 inducible coiled-coil 1), proteins that interact with ULK1. Hypoxia or glutamine deprivation, which inhibit MTORC1, was also able to increase the phosphorylation in a manner dependent upon ULK1 and ULK2. Blocking the BECN1 phosphorylation by replacing Ser30 with alanine suppressed the amino acid starvation-induced activation of the ATG14-containing PIK3C3/VPS34 (phosphatidylinositol 3-kinase catalytic subunit type 3) kinase, and reduced autophagy flux and the formation of phagophores and autophagosomes. The Ser30-to-Ala mutation did not affect the ULK1-mediated phosphorylations of BECN1 Ser15 or ATG14 Ser29, indicating that the BECN1 Ser30 phosphorylation might regulate autophagy independently of those 2 sites. Taken together, these results demonstrate that BECN1 Ser30 is a ULK1 target site whose phosphorylation activates the ATG14-containing PIK3C3 complex and stimulates autophagosome formation in response to amino acid starvation, hypoxia, and MTORC1 inhibition.

LncRNA MALAT1 protects cardiomyocytes from isoproterenol‐induced apoptosis through sponging miR‐558 to enhance ULK1‐mediated protective autophagy

“…As to the apoptosis rates in Figure 4e Park et al, 2018). It showed in Figure 4f that ISO intervention induced the upregulations of ULK1, beclin1, and LC3-II proteins, whereas ULK1 downregulation by specific siRNA reversed these upregulations and decreased autophagy.…”

So Many Roads: the Multifaceted Regulation of Autophagy Induction

“…One of these complexes, the BECN1 complex, promotes the generation of phosphatidylinositol 3-phosphate (PI3-P) lipids that are vital to the formation of the initial phagophore structure (2). ULK1 phosphorylates BECN1 at serines 15 and 30 and causes dissociation of BECN1 from the apoptosis regulatory protein BCL2 (45)(46)(47). Additionally, ULK1 phosphorylates ATG14 at ULK1 and ULK2 contain conserved serine/threonine kinase (S/TK) domains and conserved C-terminal domains (CTD) that are crucial for binding with RB1CC1.…”

“…ATG13 and ATG101 interact via the HORMA domain. serine 29, which enhances ATG14:BECN1 binding and promotes the formation of the autophagy PIK3C3 complexes (47). Upon generation of PI3-P lipids, WIPI2 binds and recruits the LC3 conjugation complex: autophagy-related 5 (ATG5), autophagy-related 12 (ATG12), and autophagy-related 16 (ATG16) (48).…”

Oral Microbes and Mucosal Dendritic Cells, “Spark and Flame” of Local and Distant Inflammatory Diseases

“…Binding of the antiapoptotic protein BCL2 to Beclin 1 and phosphorylation of Beclin 1 by Akt and EGFR (epidermal growth factor receptor) inhibit autophagy [94,95]. On the other hand, Beclin 1 phosphorylation by ULK1, MAPKAPK (mitogen-activated protein kinase−activated protein kinase) 2 and 3, AMPK, and DAPK (death-associated protein kinase) has been reported to promote autophagy [96][97][98][99]. In high-nutrient conditions, mTORC1 binds to and phosphorylates ATG13 and ULK1 [100].…”