title: La3+ binds to BiP/GRP78 and induces unfolded protein response in HepG2 cells.
abstract: The effects of La3+ on the unfolded protein response signaling pathways were investigated in human hepatoblastoma HepG2 cells. Our data showed that La3+ could induce unfolded protein response in HepG2 cells, including a significant increase of BiP/GRP78 level, which is an important ER residential chaperone and an ER stress hallmark, in a concentration and time-dependent manner, UPR transducer IRE1 phosphorylation and splicing activation IRE1 downstream substrate XBP1 mRNA. By using La3+-affinity chromatography, the possible cellular target of La3+ leading to UPR events was shown to be the ER residential chaperone BiP/GRP78. BiP/GRP78 was shown to be a La3+ binding protein and the interaction of La3+ with BiP/GRP78 resulted in dissociation of BiP-IRE1 complexes. La3+ induced dissociation of the BiP/GRP78-IRE1 complex was in a time and concentration manner. The apparent dissociation constant was estimated to be 4 nM. In addition, La3+ was observed to slightly stimulate the production of cellular ROS and cause alteration of intracellular Ca2+, indicating the possible involvement of ROS and Ca2+ alteration in La3+ induced UPR. The present work provides a new perspective for understanding the biological and toxicological effects of La3+.
authors.affiliation: State Key Laboratories for Natural and Biomimetic Drugs and Department of Chemical Biology, School of Pharmaceutical Science, Peking University, Beijing 100191, PR China.
authors.forename: Chenxi
authors.initials: C
authors.lastname: Shen
authors.forename: Zaiquan
authors.initials: Z
authors.lastname: Li
authors.forename: Xiaoda
authors.initials: X
authors.lastname: Yang
authors.forename: Kui
authors.initials: K
authors.lastname: Wang
mesh_terms: D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002846:Chromatography, Affinity; D004268:DNA-Binding Proteins / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004722:Endoribonucleases / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D028581:Lanthanoid Series Elements / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D000071701:Regulatory Factor X Transcription Factors; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics; D014407:Tumor Cells, Cultured; D000071717:X-Box Binding Protein 1
chemical_list: D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D028581:Lanthanoid Series Elements; D018832:Molecular Chaperones; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C528229:ERN1 protein, human; D017346:Protein Serine-Threonine Kinases; D004722:Endoribonucleases; D002118:Calcium