title: HSF1-mediated BAG3 expression attenuates apoptosis in 4-hydroxynonenal-treated colon cancer cells via stabilization of anti-apoptotic Bcl-2 proteins.
abstract: 4-Hydroxynonenal (HNE) is a pro-apoptotic electrophile generated during the spontaneous decomposition of oxidized lipids. We have previously shown that HNE activates the transcription factor, heat shock factor 1 (HSF1), and promotes cytoprotective heat shock gene expression and that silencing HSF1 sensitizes the colon cancer cell line RKO to HNE-induced apoptosis. Here we report a reduction in the anti-apoptotic proteins Bcl-X(L), Mcl-1, and Bcl-2 in HSF1-silenced RKO cells, and we examine the underlying mechanism. To investigate the regulation of the Bcl-2 family by HSF1, microarray analysis of gene expression was performed. We observed that the Hsp70 co-chaperone, BAG3 (Bcl-2-associated athanogene domain 3), is strongly induced by HNE in control but not in HSF1-silenced colon cancer cells. Silencing BAG3 expression with small interfering RNA caused a dramatic reduction in Bcl-X(L), Mcl-1, and Bcl-2 protein levels in colon cancer cells and increased apoptosis, similar to the effect of silencing HSF1. Also, immunoprecipitation experiments indicate specific interactions between BAG3, Hsp70, and the Bcl-2 family member, Bcl-X(L). Overall, our data reveal that BAG3 is HSF1-inducible and has a unique role facilitating cancer cell survival during pro-apoptotic stress by stabilizing the level of Bcl-2 family proteins.
authors.affiliation: Department of Biochemistry, Vanderbilt Institute of Chemical Biology, Center in Molecular Toxicology, and Vanderbilt-Ingram Comprehensive Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
authors.forename: Aaron T
authors.initials: AT
authors.lastname: Jacobs
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Marnett
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000447:Aldehydes / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D020411:Oligonucleotide Array Sequence Analysis; D011485:Protein Binding; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000447:Aldehydes; D004268:DNA-Binding Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D014157:Transcription Factors; C027576:4-hydroxy-2-nonenal