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Translational Regulation of Cyclooxygenase‐2 (COX2) by Cyclin‐Dependent Kinase 7 (CDK7) in Endothelial Cells
Author(s) -
Shetty Shruthi,
Spaulding Amelia M.,
Baker Cassadie,
Baine Stephen H.,
Hoyt Dale G.
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.04431
Subject(s) - eif4e , cyclin dependent kinase 7 , gene knockdown , protein kinase a , cyclin d1 , messenger rna , microbiology and biotechnology , biology , chemistry , phosphorylation , translation (biology) , cyclin dependent kinase 2 , cell cycle , biochemistry , cell , gene
Endothelial cell prostaglandins modulate the response to inflammatory stimuli. Combined treatment with E. coli endotoxin and interferon‐γ (LPS/IFN) induces cyclooxygenase‐2 (COX2) mRNA and protein. Modulation of COX2 expression may be therapeutically useful in different inflammatory states. Given the induction of COX2 mRNA by LPS/IFN, it was hypothesized that depletion of the transcription‐stimulating enzyme, cyclin‐dependent kinase 7 (CDK7), would antagonize induction of COX2. Here, mouse aortic endothelial cells were treated with CDK7 or non‐targeted siRNA, followed by LPS/IFN. Contrary to our expectations, knocking down CDK7 super‐induced the expression of COX2, without affecting mRNA or turnover of the protein. This suggested that CDK7 depletion increased protein synthesis. Here, signaling mechanisms known to regulate translation were investigated. CDK7 knockdown increased phosphorylation at Serine 209 of the mRNA cap‐binding translation initiation factor, eIF4E. Knockdown also increased cap‐binding activity of eIF4E. CDK7 depletion increased phosphorylation of the eIF4E repressor, 4EBP1, and decreased its association with eIF4E. Finally, increased phosphorylation of ribosomal protein S6 (RPS6), a component of the 40S ribosomal subunit, was also seen in the absence of CDK7, indicating increased translation. The results suggest that CDK7 represses COX2 expression by limiting translation through effects on RPS6, eIF4E and/or 4EBP1. CDK7 may serve as a target for the manipulation of COX2 expression in endothelial cells. Support or Funding Information Support was received from the Popat Patil Fellowship (SS).