title: FBXO6-Mediated Ubiquitination and Degradation of Ero1L Inhibits Endoplasmic Reticulum Stress-Induced Apoptosis.
abstract: OBJECTIVE
  FBXO6 is the substrate recognition component of a Skp1-Cullin1-F-box protein (SCF) ubiquitin E3 ligase complex, recognizing the chitobiose in unfolded N-glycoprotein to target glycoproteins for polyubiquitination and degradation. Although how FBXO6 recognizes glycoprotein has been fully investigated, the ubiquitination substrates of FBXO6 remain largely unknown. Previously, we have systematically identified the glycoproteins that interact with FBXO6 in an N-glycan dependent manner by LC/MS spectrum and confirmed the interaction between FBXO6 and glycosylated Ero1L, a protein disulfide oxidase in endoplasmic reticulum (ER).
  
  
  METHODS
  The relationship between endogenous Ero1L and exogenous Flag-FBXO6 were determined by Western blot. In vivo ubiquitination assay was used to detect the direct effect of FBXO6 in the regulation of Ero1L. Both CCK8 and FACS assays were used to determine the apoptosis ratio of cells after treatments.
  
  
  RESULTS
  Ero1L is a ubiquitination substrate of FBXO6. FBXO6 mediates the degradation of Ero1L through a ubiquitylation-dependent pathway. Overexpression of FBXO6 increased the polyubiquitination and decreased the stability of Ero1L, whereas inhibition of FBXO6 prolonged the half-life of Ero1L. Functionally, we show that FBXO6 inhibits ER stress-induced apoptosis by modulating the protein level of Ero1L.
  
  
  CONCLUSIONS
  Collectively, our results demonstrate FBXO6 as a functional E3 ubiquitin ligase for Ero1L that plays a critical role in inhibiting ER stress-induced apoptosis.
authors.affiliation: Hubei Key Laboratory for Kidney Disease Pathogenesis and Intervention, Huangshi Cental Hospital of Edong Healthcare Group, Hubei Polytechnic University School of Medicine, Huangshi, Hubei, PR China.
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.forename: Lang-Huan
authors.initials: LH
authors.lastname: Duan
authors.forename: Peng-Cheng
authors.initials: PC
authors.lastname: Luo
authors.forename: Gang
authors.initials: G
authors.lastname: Hu
authors.forename: Xin
authors.initials: X
authors.lastname: Yu
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.forename: Han
authors.initials: H
authors.lastname: Lu
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
mesh_terms: D000072283:A549 Cells; D017209:Apoptosis; D059865:Endoplasmic Reticulum Stress; D006367:HeLa Cells; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D055550:Protein Stability; D059748:Proteolysis; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D008562:Membrane Glycoproteins; C405327:ERO1A protein, human; D010088:Oxidoreductases; C479752:FBXO6 protein, human; D044843:SKP Cullin F-Box Protein Ligases