ATM, a DNA damage-inducible kinase, contributes to activation by high NaCl of the transcription factor TonEBP/OREBP.
High NaCl activates the transcription factor tonicity-responsive enhancer/osmotic response element-binding protein (TonEBP/OREBP), resulting in increased transcription of several protective genes, including the glycine betaine/gamma-aminobutyric acid transporter (BGT1). High NaCl damages DNA, and DNA damage activates ataxia telangiectasia mutated (ATM) kinase through autophosphorylation on Ser-1981. TonEBP/OREBP contains ATM consensus phosphorylation sites at Ser-1197, Ser-1247, and Ser-1367. The present studies test whether ATM is involved in activation of TonEBP/OREBP by high NaCl. We find that raising osmolality from 300 to 500 mosmol/kg by adding NaCl activates ATM, as indicated by phosphorylation at Ser-1981. High urea and radiation also activate ATM, but they do not increase TonEBP/OREBP transcriptional activity like high NaCl does. Wortmannin, which inhibits ATM, reduces NaCl-induced TonEBP/OREBP transcriptional activation and BGT1 mRNA increase. Overexpression of wild-type TonEBP/OREBP increases ORE/TonE reporter activity much more than does overexpression of TonEBP/OREBP S1197A, S1247A, or S1367A. In AT cells (which express nonfunctional ATM), TonEBP/OREBP transcriptional and transactivating activity are further increased by expression of wild-type ATM but not of S1981A ATM. TonEBP/OREBP reciprocally coimmunoprecipitates with ATM kinase, demonstrating physical association. Additionally, antibody to ATM kinase supershifts TonEBP/OREBP bound to its cognate ORE/TonE DNA element. In AT cells, wortmannin further decreases high NaCl-induced increase in transcriptional activity, consistent with participation of signaling kinase(s) in addition to ATM. In conclusion, signaling via ATM is necessary for full activation of TonEBP/OREBP by high NaCl, but it is not sufficient.
Irarrazabal
Carlos E
CE
National Heart, Lung, and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892-1603, USA. irarrazc@nhlbi.nih.gov
Liu
Jennifer C
JC
Burg
Maurice B
MB
Ferraris
Joan D
JD
D064007:Ataxia Telangiectasia Mutated Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins; D002460:Cell Line; D004249:DNA Damage; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D050485:GABA Plasma Membrane Transport Proteins; D006801:Humans; D050778:NFATC Transcription Factors; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D050485:GABA Plasma Membrane Transport Proteins; D050778:NFATC Transcription Factors; D012333:RNA, Messenger; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C072207:betaine plasma membrane transport proteins; D012965:Sodium Chloride; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases