title: Brassinosteroid nuclear signaling recruits HSP90 activity.
abstract: Heat shock protein 90 (HSP90) controls a number of developmental circuits, and serves a sophisticated and highly regulatory function in signaling pathways. Brassinosteroids (BRs) control many aspects of plant development. Genetic, physiological, cytological, gene expression, live cell imaging, and pharmacological approaches provide conclusive evidence for HSP90 involvement in Arabidopsis thalianaBR signaling. Nuclear-localized HSP90s translocate to cytoplasm when their activity is blocked by the HSP90 inhibitor geldanamycin (GDA). GDA treatment promoted the export of BIN2, a regulator of BR signaling, from the nucleus into the cytoplasm, indicating that active HSP90 is required to sustain BIN2 in the nucleus. HSP90 nuclear localization was inhibited by brassinolide (BL). HSP90s interact with BIN2 in the nucleus of untreated cells and in the cytoplasm of BL-treated cells, showing that the site-specific action of HSP90 on BIN2 is controlled by BRs. GDA and BL treatments change the expression of a common set of previously identified BR-responsive genes. This highlights the effect of active HSP90s on the regulation of BR-responsive genes. Our observations reveal that HSP90s have a central role in sustaining BIN2 nuclear function. We propose that BR signaling is mediated by HSP90 activity and via trafficking of BIN2-HSP90 complexes into the cytoplasm.
authors.affiliation: Laboratory of Molecular Biology, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
authors.forename: Despina
authors.initials: D
authors.lastname: Samakovli
authors.forename: Theoni
authors.initials: T
authors.lastname: Margaritopoulou
authors.forename: Constantinos
authors.initials: C
authors.lastname: Prassinos
authors.forename: Dimitra
authors.initials: D
authors.lastname: Milioni
authors.forename: Polydefkis
authors.initials: P
authors.lastname: Hatzopoulos
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D016227:Benzoquinones / Q000494:pharmacology; D060406:Brassinosteroids / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006706:Homeostasis / Q000187:drug effects / Q000235:genetics; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism; D021382:Protein Sorting Signals; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D016227:Benzoquinones; D060406:Brassinosteroids; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D011494:Protein Kinases; D021382:Protein Sorting Signals; C466978:Hsp90-1 protein, Arabidopsis; C500134:Hsp90-3 protein, Arabidopsis; C448985:At4g18710 protein, Arabidopsis; C001277:geldanamycin
keywords: Arabidopsis thaliana; BIN2; brassinosteroid signaling; gene expression; heat shock protein 90 (HSP90)