Alternative splicing of platelet cyclooxygenase-2 mRNA in patients after coronary artery bypass grafting.
Recently, we cloned from platelet mRNA a novel cyclooxygenase (COX)-2 splice variant, designated COX-2a, which is characterized by a partial deletion of exon 5. Preliminary studies of mRNA distribution of COX-2 isoforms in platelets from coronary artery bypass grafting (CABG) patients showed a variable increase in COX-2a mRNA expression after cardiac surgery. Thus, we assessed whether this variant may play a functional role in these patients. We report a marked (about 200-fold) increase in the expression of COX-2a mRNA after CABG. Evidence is presented that ribosomal frame-shifting may correct the coding sequence resulting in the expression of a full-length COX-2a protein. In addition, a reading frame-corrected COX-2a mutant (COX-2a delta G) was generated by site-directed mutagenesis and expressed in COS-7 cells using an adenoviral expression system. However, COX-2a protein was not active in terms of prostaglandin formation. Thus, alternative mRNA splicing might represent an intriguing posttranscriptional mechanism to oppose a transcriptional activation of the COX-2 gene. Evolutionary, this mechanism may prevent COX-2-dependent thromboxane synthesis in the platelet, which would potentiate the likelihood of thrombosis; pharmacologically, this mechanism would prevent an aspirin-insensitive pathway of thromboxane formation.
Censarek
Petra
P
Institut für Pharmakologie und Klinische Pharmakologie Universitätsklinikum Duesseldorf, Germany.
Steger
Gerhard
G
Paolini
Carla
C
Hohlfeld
Thomas
T
Grosser
Tilo
T
Zimmermann
Norbert
N
Fleckenstein
Diana
D
Schrör
Karsten
K
Weber
Artur-Aron
AA
D000284:Administration, Oral; D017398:Alternative Splicing; D000818:Animals; D001241:Aspirin / Q000008:administration & dosage; D001483:Base Sequence; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology*; D019556:COS Cells; D002522:Chlorocebus aethiops; D001026:Coronary Artery Bypass; D003324:Coronary Artery Disease / Q000188:drug therapy / Q000201:enzymology / Q000601:surgery*; D051546:Cyclooxygenase 2 / Q000097:blood* / Q000235:genetics; D004351:Drug Resistance; D011464:Epoprostenol / Q000378:metabolism; D018965:Frameshifting, Ribosomal; D006801:Humans; D007527:Isoenzymes / Q000097:blood; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage; D012333:RNA, Messenger / Q000097:blood*; D013928:Thromboxane A2 / Q000378:metabolism; D014162:Transfection; D016896:Treatment Outcome; D015854:Up-Regulation
D007527:Isoenzymes; D010975:Platelet Aggregation Inhibitors; D012333:RNA, Messenger; D013928:Thromboxane A2; D011464:Epoprostenol; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D001241:Aspirin