title: Hsp90 transcriptionally and post-translationally regulates the expression of NDRG1 and maintains the stability of its modifying kinase GSK3beta.
abstract: N-myc downstream-regulated gene 1 (NRDG1) is a stress-induced protein whose putative function is suppression of tumor metastasis. A recent proteonomic study showed NDRG1 interacts with the molecular chaperone heat shock protein 90 (Hsp90). From their reported association, we investigated if NDRG1 is dependent on Hsp90 for its stability and is therefore a yet unidentified Hsp90 client protein. Here, we demonstrate that endogenous NDRG1 and Hsp90 physically associate in hepatocellular cancer cell lines. However, geldanamycin (GA)-mediated inhibition of Hsp90 did not disrupt their interaction or result in NDRG1 protein destabilization. On the contrary, inhibition of Hsp90 led to a transcriptional increase of NDRG1 protein which was associated with cell growth arrest. We also observed that GA inhibited the phosphorylation of NDRG1 by targeting its regulating kinases, serum- and glucocorticoid-induced kinase 1 (SGK1) and glycogen synthase kinase 3 beta (GSK3beta). We demonstrate that in the presence of GA, GSK3beta protein and activity were decreased thus indicating that Hsp90 is necessary for GSK3beta stability. Taken together, our data demonstrate that NDRG1 is not a classic client protein but interacts with Hsp90 and is still dually regulated by Hsp90 at a transcriptional and post-translational level. Finally, we suggest for the first time GSK3beta as a new client protein of Hsp90.
authors.affiliation: Department of Visceral Surgery, Inselspital, Bern University Hospital and University of Bern, Switzerland.
authors.forename: Vanessa M
authors.initials: VM
authors.lastname: Banz
authors.forename: Michaela
authors.initials: M
authors.lastname: Medová
authors.forename: Adrian
authors.initials: A
authors.lastname: Keogh
authors.forename: Cynthia
authors.initials: C
authors.lastname: Furer
authors.forename: Yitzhak
authors.initials: Y
authors.lastname: Zimmer
authors.forename: Daniel
authors.initials: D
authors.lastname: Candinas
authors.forename: Deborah
authors.initials: D
authors.lastname: Stroka
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism; D016227:Benzoquinones / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004795:Enzyme Stability / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000737:chemistry* / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D020298:U937 Cells; D000099259:N-myc Downstream-Regulated Gene 1 Protein
chemical_list: D000251:Adenosine Triphosphatases; D016227:Benzoquinones; D018797:Cell Cycle Proteins; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D018841:HSP90 Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D047029:Lactams, Macrocyclic; D012333:RNA, Messenger; D000099259:N-myc Downstream-Regulated Gene 1 Protein; C000605506:GSK3B protein, human; C001277:geldanamycin