Phosphatidylinositol 3-kinase mediates activation of ATM by high NaCl and by ionizing radiation: Role in osmoprotective transcriptional regulation.
High NaCl causes DNA double-strand breaks and activates the transcription factor, TonEBP/OREBP, resulting in increased transcription of several protective genes, including those involved in accumulation of compatible organic osmolytes. Several kinases are known to contribute to signaling activation of TonEBP/OREBP, including ATM, which is a member of the phosphatidylinositol 3-kinase (PI3K)-like kinase family and is activated by DNA double-strand breaks. The purpose of the present studies was to investigate a possible role of PI3K Class IA (PI3K-IA). We found that high NaCl increases PI3K-IA lipid kinase activity. Inhibiting PI3K-IA either by expressing a dominant negative of its regulatory subunit, p85, or by small interfering RNA-mediated knockdown of its catalytic subunit, p110alpha, reduces high NaCl-induced increases in TonEBP/OREBP transcriptional activity and transactivation, but not nuclear translocation of TonEBP/OREBP, or increases in its abundance. Further, suppression of PI3K-IA inhibits the activation of ATM that is caused by either ionizing radiation or high NaCl. High NaCl-induced increase in TonEBP/OREBP activity is reduced equally by inhibition of ATM or PI3K-IA, and the effects are not additive. The conclusions are as follows: (i) PI3K-IA activity is necessary for both high NaCl- and ionizing radiation-induced activation of ATM and (ii) high NaCl activates PI3K-IA, which, in turn, contributes to full activation of TonEBP/OREBP via ATM.
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@mhlbi.nih.gov
Burg
Maurice B
MB
Ward
Stephen G
SG
Ferraris
Joan D
JD
D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D019169:Jurkat Cells; D050778:NFATC Transcription Factors / Q000235:genetics; D009995:Osmosis / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000235:genetics; D011839:Radiation, Ionizing; D012965:Sodium Chloride / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects* / Q000528:radiation effects*; D015533:Transcriptional Activation / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050778:NFATC Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D034741:RNA, Small Interfering; D012965:Sodium Chloride; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human