O-GlcNAcylation of eIF2α regulates the phospho-eIF2α-mediated ER stress response.
O-GlcNAcylation is highly involved in cellular stress responses including the endoplasmic reticulum (ER) stress response. For example, glucosamine-induced flux through the hexosamine biosynthetic pathway can promote ER stress and ER stress inducers can change the total cellular level of O-GlcNAcylation. However, it is largely unknown which component(s) of the unfolded protein response (UPR) is directly regulated by O-GlcNAcylation. In this study, eukaryotic translation initiation factor 2α (eIF2α), a major branch of the UPR, was O-GlcNAcylated at Ser 219, Thr 239, and Thr 241. Upon ER stress, eIF2α is phosphorylated at Ser 51 by phosphorylated PKR-like ER kinase and this inhibits global translation initiation, except for that of specific mRNAs, including activating transcription factor 4, that induce stress-responsive genes such as C/EBP homologous protein (CHOP). Hyper-O-GlcNAcylation induced by O-GlcNAcase inhibitor (thiamet-G) treatment or O-GlcNAc transferase (OGT) overexpression hindered phosphorylation of eIF2α at Ser 51. The level of O-GlcNAcylation of eIF2α was changed by dithiothreitol treatment dependent on its phosphorylation at Ser 51. Point mutation of the O-GlcNAcylation sites of eIF2α increased its phosphorylation at Ser 51 and CHOP expression and resulted in increased apoptosis upon ER stress. These results suggest that O-GlcNAcylation of eIF2α affects its phosphorylation at Ser 51 and influences CHOP-mediated cell death. This O-GlcNAcylation of eIF2α was reproduced in thiamet-G-injected mouse liver. In conclusion, proper regulation of O-GlcNAcylation and phosphorylation of eIF2α is important to maintain cellular homeostasis upon ER stress.
Department of Integrated OMICS for Biomedical Science, Yonsei University, Seoul 120-749, Republic of Korea.
Insook
I
Jang
Department of Integrated OMICS for Biomedical Science, Yonsei University, Seoul 120-749, Republic of Korea.
Han Byeol
HB
Kim
Department of Integrated OMICS for Biomedical Science, Yonsei University, Seoul 120-749, Republic of Korea.
Hojoong
H
Seo
Division of Mass Spectrometry Research, Korea Basic Science Institute, 162 Yeongudanjiro, Ochang, Cheongju 363-883, Republic of Korea.
Jin Young
JY
Kim
Department of Biochemistry and Molecular Biology, Integrated Genomic Research Center for Metabolic Regulation, Institute of Genetic Science, Yonsei University College of Medicine, Seoul 120-749, Republic of Korea.
Hyeonjin
H
Choi
Division of Mass Spectrometry Research, Korea Basic Science Institute, 162 Yeongudanjiro, Ochang, Cheongju 363-883, Republic of Korea.
Jong Shin
JS
Yoo
Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul 120-749, Republic of Korea.
Jae-woo
JW
Kim
Department of Integrated OMICS for Biomedical Science, Yonsei University, Seoul 120-749, Republic of Korea. Electronic address: chojw311@yonsei.ac.kr.
Jin Won
JW
Cho
D000117:Acetylglucosamine / Q000378:metabolism*; D000818:Animals; D059865:Endoplasmic Reticulum Stress / Q000235:genetics; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D056945:Hep G2 Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000235:genetics; D056811:Unfolded Protein Response; D019892:eIF-2 Kinase / Q000378:metabolism*
D015852:Eukaryotic Initiation Factor-2; D017351:N-Acetylglucosaminyltransferases; C449880:O-GlcNAc transferase; D019892:eIF-2 Kinase; D000117:Acetylglucosamine
Apoptosis; CHOP; ER stress; O-GlcNAc; eIF2α; p-eIF2α