title: Nuclear redistribution of tonicity-responsive enhancer binding protein requires proteasome activity.
abstract: Tonicity-responsive enhancer binding protein (TonEBP) is the transcription factor that regulates tonicity-responsive expression of the genes for the sodium-myo-inositol cotransporter (SMIT) and the sodium-chloride-betaine cotransporter (BGT1). Hypertonicity stimulates the activity of TonEBP due to a combination of increased protein abundance and increased nuclear distribution (proportion of TonEBP that is in the nucleus). We found that inhibitors of proteasome activity markedly reduce the induction of SMIT and BGT1 mRNA in response to hypertonicity. These inhibitors also reduce hypertonicity-induced stimulation of expression of a reporter gene controlled by the tonicity-responsive enhancer. Western and immunohistochemical analyses revealed that the proteasome inhibitors reduce the hypertonicity-induced increase of TonEBP in the nucleus by inhibiting its nuclear redistribution without affecting its abundance. Although the nuclear distribution of TonEBP is sensitive to inhibition of proteasome activity as is that of nuclear factor (NF)-kappaB, the signaling pathways appear to be different in that hypertonicity does not affect the nuclear distribution of NF-kappaB. Conversely, treatment with tumor necrosis factor-alpha increases the nuclear distribution of NF-kappaB but not TonEBP.
authors.affiliation: Division of Nephrology, School of Medicine, The Johns Hopkins University, Baltimore, Maryland 21205, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Woo
authors.forename: D
authors.initials: D
authors.lastname: Maouyo
authors.forename: J S
authors.initials: JS
authors.lastname: Handler
authors.forename: H M
authors.initials: HM
authors.lastname: Kwon
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry / Q000201:enzymology / Q000235:genetics; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004285:Dogs; D004742:Enhancer Elements, Genetic / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D004693:Glucan Endo-1,3-beta-D-Glucosidase / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D006982:Hypertonic Solutions / Q000494:pharmacology; D007668:Kidney / Q000166:cytology; D007976:Leupeptins / Q000494:pharmacology; D008565:Membrane Proteins; D009097:Multienzyme Complexes / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000032:analysis; D046988:Proteasome Endopeptidase Complex; D012333:RNA, Messenger / Q000235:genetics; D027981:Symporters; D015534:Trans-Activators / Q000032:analysis / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D015853:Cysteine Proteinase Inhibitors; D006360:Heat-Shock Proteins; D006982:Hypertonic Solutions; D007976:Leupeptins; D008565:Membrane Proteins; D009097:Multienzyme Complexes; D016328:NF-kappa B; D012333:RNA, Messenger; D027981:Symporters; D015534:Trans-Activators; C073884:SLC5A3 protein, human; C117939:1,3-beta-glucanosyltransferase; D004693:Glucan Endo-1,3-beta-D-Glucosidase; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde