title: PEBP1, a RAF kinase inhibitory protein, negatively regulates starvation-induced autophagy by direct interaction with LC3.
abstract: Autophagy plays a critical role in maintaining cell homeostasis in response to various stressors through protein conjugation and activation of lysosome-dependent degradation. MAP1LC3B/LC3B (microtubule- associated protein 1 light chain 3 β) is conjugated with phosphatidylethanolamine (PE) in the membranes and regulates initiation of autophagy through interaction with many autophagy-related proteins possessing an LC3-interacting region (LIR) motif, which is composed of 2 hydrophobic amino acids (tryptophan and leucine) separated by 2 non-conserved amino acids (WXXL). In this study, we identified a new putative LIR motif in PEBP1/RKIP (phosphatidylethanolamine binding protein 1) that was originally isolated as a PE-binding protein and also a cellular inhibitor of MAPK/ERK signaling. PEBP1 was specifically bound to PE-unconjugated LC3 in cells, and mutation (WXXL mutated to AXXA) of this LIR motif disrupted its interaction with LC3 proteins. Interestingly, overexpression of PEBP1 significantly inhibited starvation-induced autophagy by activating the AKT and MTORC1 (mechanistic target of rapamycin [serine/threonine kinase] complex 1) signaling pathway and consequently suppressing the ULK1 (unc-51 like autophagy activating kinase 1) activity. In contrast, ablation of PEBP1 expression dramatically promoted the autophagic process under starvation conditions. Furthermore, PEBP1 lacking the LIR motif highly stimulated starvation-induced autophagy through the AKT-MTORC1-dependent pathway. PEBP1 phosphorylation at Ser153 caused dissociation of LC3 from the PEBP1-LC3 complex for autophagy induction. PEBP1-dependent suppression of autophagy was not associated with the MAPK pathway. These findings suggest that PEBP1 can act as a negative mediator in autophagy through stimulation of the AKT-MTORC1 pathway and direct interaction with LC3.
authors.affiliation: a Department of Biochemistry and Convergence Medical Sciences , Institute of Health Sciences, Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Hae Sook
authors.initials: HS
authors.lastname: Noh
authors.affiliation: b Biomedical Research Institute of Gyeongsang National University Hospital , Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Young-Sool
authors.initials: YS
authors.lastname: Hah
authors.affiliation: a Department of Biochemistry and Convergence Medical Sciences , Institute of Health Sciences, Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Sahib
authors.initials: S
authors.lastname: Zada
authors.affiliation: a Department of Biochemistry and Convergence Medical Sciences , Institute of Health Sciences, Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Ji Hye
authors.initials: JH
authors.lastname: Ha
authors.affiliation: a Department of Biochemistry and Convergence Medical Sciences , Institute of Health Sciences, Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Gyujin
authors.initials: G
authors.lastname: Sim
authors.affiliation: a Department of Biochemistry and Convergence Medical Sciences , Institute of Health Sciences, Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Jin Seok
authors.initials: JS
authors.lastname: Hwang
authors.affiliation: a Department of Biochemistry and Convergence Medical Sciences , Institute of Health Sciences, Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Trang Huyen
authors.initials: TH
authors.lastname: Lai
authors.affiliation: a Department of Biochemistry and Convergence Medical Sciences , Institute of Health Sciences, Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Huynh Quoc
authors.initials: HQ
authors.lastname: Nguyen
authors.affiliation: c School of Biosystem and Biomedical Science, College of Health Science , Korea University , Seoul , Korea.
authors.forename: Jae-Yong
authors.initials: JY
authors.lastname: Park
authors.affiliation: d Department of Anatomy and Convergence Medical Sciences, Institute of Health Sciences , Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Hyun Joon
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: e Department of Oral and Maxillofacial Surgery, Institute of Health Sciences , Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: June-Ho
authors.initials: JH
authors.lastname: Byun
authors.affiliation: f Department of Internal Medicine , Institute of Health Sciences, Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Jong Ryeal
authors.initials: JR
authors.lastname: Hahm
authors.affiliation: a Department of Biochemistry and Convergence Medical Sciences , Institute of Health Sciences, Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Kee Ryeon
authors.initials: KR
authors.lastname: Kang
authors.affiliation: a Department of Biochemistry and Convergence Medical Sciences , Institute of Health Sciences, Gyeongsang National University School of Medicine , JinJu , Korea.
authors.forename: Deok Ryong
authors.initials: DR
authors.lastname: Kim
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000071182:Autophagosomes / Q000378:metabolism / Q000648:ultrastructure; D001343:Autophagy; D005508:Food Deprivation / Q000502:physiology*; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D049488:Phosphatidylethanolamine Binding Protein / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D015398:Signal Transduction
chemical_list: C502070:MAP1LC3B protein, human; D008869:Microtubule-Associated Proteins; C511482:PEBP1 protein, human; D049488:Phosphatidylethanolamine Binding Protein; D020928:Mitogen-Activated Protein Kinases
keywords: ERK pathway; LC3; LIR motif; MTOR; PEBP1/RKIP; autophagy