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C/EBP{beta} and its binding element are required for NF{kappa}B-induced COX2 expression following hypertonic stress
Jing Chen1, Min Zhao, Reena Rao
1Division of Nephrology, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USA.
The Journal of Biological Chemistry
|February 17, 2005
Summary
Nuclear factor C/EBPbeta is essential for NFkappaB to induce COX2 expression in renal cells under hypertonic stress. Blocking C/EBPbeta significantly suppresses COX2, highlighting its dominant role in this process.
Area of Science:
- Cellular and Molecular Biology
- Renal Physiology
- Transcription Factor Regulation
Background:
- Nuclear factor kappa B (NFkappaB) mediates cyclooxygenase-2 (COX2) expression in renal medullary interstitial cells (RMICs).
- C/EBPbeta, a nuclear factor, can bind and modify NFkappaB activity.
- The COX2 promoter contains adjacent NFkappaB and C/EBPbeta binding sites.
Purpose of the Study:
- To investigate the cooperative role of NFkappaB and C/EBPbeta in inducing COX2 expression under hypertonic stress.
- To determine the dominant transcription factor pathway regulating COX2 induction in RMICs.
Main Methods:
- Utilized immunoblot analysis to measure COX2 expression.
- Employed mutant IkappaB (IkappaBm) to block NFkappaB activation.
- Created COX2 promoter mutations targeting NFkappaB and C/EBPbeta sites.
- Used dominant-negative C/EBPbeta-p20 transduction in RMICs.
- Performed co-immunoprecipitation to assess protein interactions.
Main Results:
- Hypertonicity markedly induced COX2 expression in RMICs, dependent on NFkappaB activation.
- Mutation of the NFkappaB site did not abolish tonicity-induced COX2 reporter activity.
- Mutation of the C/EBPbeta site significantly reduced hypertonicity-induced COX2 reporter activity.
- C/EBPbeta-p20 suppressed hypertonic COX2 induction similarly to IkappaBm.
- Physical association between C/EBPbeta and NFkappaB p65 was enhanced by hypertonic stress.
Conclusions:
- C/EBPbeta is required for NFkappaB-mediated transcriptional activation of COX2.
- The C/EBPbeta pathway plays a dominant role in regulating hypertonicity-induced COX2 expression in RMICs.
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