Activator protein-1 contributes to high NaCl-induced increase in tonicity-responsive enhancer/osmotic response element-binding protein transactivating activity.
Tonicity-responsive enhancer/osmotic response element-binding protein (TonEBP/OREBP) is a Rel protein that activates transcription of osmoprotective genes at high extracellular NaCl. Other Rel proteins NFAT1-4 and NF-kappaB complex with activator protein-1 (AP-1) to transactivate target genes through interaction at composite NFAT/NF-kappaB.AP-1 sites. TonEBP/OREBP target genes commonly have one or more conserved AP-1 binding sites near TonEBP/OREBP cognate elements (OREs). Also, TonEBP/OREBP and the AP-1 proteins c-Fos and c-Jun are all activated by high NaCl. We now find, using an ORE.AP-1 reporter from the target aldose reductase gene or the same reporter with a mutated AP-1 site, that upon stimulation by high extracellular NaCl, 1) the presence of a wild type, but not a mutated, AP-1 site contributes to TonEBP/OREBP-dependent transcription and 2) AP-1 dominant negative constructs inhibit TonEBP/OREBP-dependent transcription provided the AP-1 site is not mutated. Using supershifts and an ORE.AP-1 probe, we find c-Fos and c-Jun present in combination with TonEBP/OREBP. Also, c-Fos and c-Jun coimmunoprecipitate with TonEBP/OREBP, indicating physical association. Small interfering RNA knockdown of either c-Fos or c-Jun inhibits high NaCl-induced increase of mRNA abundance of the TonEBP/OREBP target genes AR and BGT1. Furthermore, a dominant negative AP-1 also reduces high NaCl-induced increase of TonEBP/OREBP transactivating activity. Inhibition of p38, which is known to stimulate TonEBP/OREBP transcriptional activity, reduces high NaCl-dependent transcription of an ORE.AP-1 reporter only if the AP-1 site is intact. Thus, AP-1 is part of the TonEBP/OREBP enhanceosome, and its role in high NaCl-induced activation of TonEBP/OREBP may require p38 activity.
Irarrazabal
Carlos E
CE
Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung, and Blood Institute, National Institutes of Health/DHHS, 10 Center Drive, Bethesda, MD 20892, USA.
Williams
Chester K
CK
Ely
Megan A
MA
Birrer
Michael J
MJ
Garcia-Perez
Arlyn
A
Burg
Maurice B
MB
Ferraris
Joan D
JD
D000449:Aldehyde Reductase / Q000235:genetics; D000818:Animals; D051399:Aquaporin 2 / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004285:Dogs; D050485:GABA Plasma Membrane Transport Proteins; D016762:Genes, fos; D016758:Genes, jun; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D050778:NFATC Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D027981:Symporters / Q000235:genetics; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection
C496024:Aqp2 protein, mouse; D051399:Aquaporin 2; D002352:Carrier Proteins; D017931:DNA Primers; D050485:GABA Plasma Membrane Transport Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D050778:NFATC Transcription Factors; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D027981:Symporters; D018808:Transcription Factor AP-1; C072207:betaine plasma membrane transport proteins; C073884:SLC5A3 protein, human; D012965:Sodium Chloride; D000449:Aldehyde Reductase