title: Autophagy negatively regulates cancer cell proliferation via selectively targeting VPRBP.
abstract: There have been multiple lines of evidence suggesting that autophagy selectively targets signalling proteins and regulates cancer cell signalling in addition to bulk clearance of long-lived proteins and organelles. Protein degradation through autophagy requires receptor protein LC3B to sequester the substrates into the autophagosome. In the present study, we screened LC3B (light-chain 3B)-binding partners and identified autophagic substrates in cancer cells. With lung cancer NCI-H1975 and oesophageal cancer KYSE30 cell lines as models, we found that VPRBP (viral protein R-binding protein) was a novel LC3B-binding protein through GST (glutathione transferase)-LC3B pull-down combined with LC-MS/MS (liquid chromatography-tandem MS) methods. Co-immunoprecipitation assay showed that VPRBP-LC3/p62 were in the same protein complex as the two cell lines. Induction of autophagy led to a down-regulation of VPRPB, which could be rescued by the inhibition of autophagy degradation by BFA1 (bafilomycin A1) and by the disruption of autophagy through ATG5-knockdown. We also found that induction of autophagy promotes VPRBP-LC3/p62 interaction. Immunohistochemical examination of human NSCLC (non-small cell lung cancer) tissues showed that VPRBP was positively correlated with p62 and negatively correlated with LC3B. Moreover, p62 and VPRBP were associated with poor prognosis in lung ADC (adenocarcinoma) (p62, P=0.019; VPRBP, P=0.005). Patients with low expression of both p62 and VPRBP showed the best prognosis.
authors.affiliation: State Key Laboratory of Molecular Oncology, Cancer Institute (Hospital), Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, People's Republic of China.
authors.forename: Bo-Shi
authors.initials: BS
authors.lastname: Wang
authors.forename: Yi-Zhen
authors.initials: YZ
authors.lastname: Liu
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jia-Jie
authors.initials: JJ
authors.lastname: Hao
authors.forename: Hai
authors.initials: H
authors.lastname: Yang
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: Wang
authors.forename: Zi-Qiang
authors.initials: ZQ
authors.lastname: Zhang
authors.forename: Qi-Min
authors.initials: QM
authors.lastname: Zhan
authors.forename: Ming-Rong
authors.initials: MR
authors.lastname: Wang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D001343:Autophagy; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008875:Middle Aged; D016877:Oxidants / Q000494:pharmacology; D011379:Prognosis; D011485:Protein Binding / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D034622:RNA Interference; D000071456:Sequestosome-1 Protein; D020123:Sirolimus / Q000494:pharmacology; D044767:Ubiquitin-Protein Ligases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000903:Antibiotics, Antineoplastic; D002352:Carrier Proteins; C502070:MAP1LC3B protein, human; D008869:Microtubule-Associated Proteins; D016877:Oxidants; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D006861:Hydrogen Peroxide; D044767:Ubiquitin-Protein Ligases; C530533:DCAF1 protein, human; D017346:Protein Serine-Threonine Kinases; D020123:Sirolimus