title: NIK is required for NF-κB-mediated induction of BAG3 upon inhibition of constitutive protein degradation pathways.
abstract: Recently, we reported that induction of the co-chaperone Bcl-2-associated athanogene 3 (BAG3) is critical for recovery of rhabdomyosarcoma (RMS) cells after proteotoxic stress upon inhibition of the two constitutive protein degradation pathways, that is, the ubiquitin-proteasome system by Bortezomib and the aggresome-autophagy system by histone deacetylase 6 (HDAC6) inhibitor ST80. In the present study, we investigated the molecular mechanisms mediating BAG3 induction under these conditions. Here, we identify nuclear factor-kappa B (NF-κB)-inducing kinase (NIK) as a key mediator of ST80/Bortezomib-stimulated NF-κB activation and transcriptional upregulation of BAG3. ST80/Bortezomib cotreatment upregulates mRNA and protein expression of NIK, which is accompanied by an initial increase in histone H3 acetylation. Importantly, NIK silencing by siRNA abolishes NF-κB activation and BAG3 induction by ST80/Bortezomib. Furthermore, ST80/Bortezomib cotreatment stimulates NF-κB transcriptional activity and upregulates NF-κB target genes. Genetic inhibition of NF-κB by overexpression of dominant-negative IκBα superrepressor (IκBα-SR) or by knockdown of p65 blocks the ST80/Bortezomib-stimulated upregulation of BAG3 mRNA and protein expression. Interestingly, inhibition of lysosomal activity by Bafilomycin A1 inhibits ST80/Bortezomib-stimulated IκBα degradation, NF-κB activation and BAG3 upregulation, indicating that IκBα is degraded via the lysosome in the presence of Bortezomib. Thus, by demonstrating a critical role of NIK in mediating NF-κB activation and BAG3 induction upon ST80/Bortezomib cotreatment, our study provides novel insights into mechanisms of resistance to proteotoxic stress in RMS.
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Rapino
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.
authors.forename: B A
authors.initials: BA
authors.lastname: Abhari
authors.affiliation: 1] Institute of Pharmaceutical Sciences, Albert-Ludwigs-University, Freiburg, Germany [2] German Cancer Consortium (DKTK), Heidelberg, Germany [3] German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Jung
authors.affiliation: 1] Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany [2] German Cancer Consortium (DKTK), Heidelberg, Germany [3] German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Fulda
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis* / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis* / Q000378:metabolism; D001343:Autophagy / Q000235:genetics; D000069286:Bortezomib / Q000008:administration & dosage; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis* / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis; D012208:Rhabdomyosarcoma / Q000235:genetics* / Q000473:pathology; D015398:Signal Transduction; D015533:Transcriptional Activation / Q000187:drug effects; D000097782:NF-kappaB-Inducing Kinase
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D000069286:Bortezomib; D051550:I-kappa B Kinase; D016328:NF-kappa B; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D000097782:NF-kappaB-Inducing Kinase; C414431:BAG3 protein, human