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Functional coupling between various phospholipase A2s and cyclooxygenases in immediate and delayed prostanoid
M Murakami1, T Kambe, S Shimbara
1Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142, Japan.
The Journal of Biological Chemistry
|January 23, 1999
Summary
Signaling phospholipase A2s (PLA2s) and cyclooxygenases (COXs) were reconstituted in cells to study prostaglandin production. Extracellular PLA2s act as paracrine amplifiers, enhancing prostaglandin synthesis in neighboring cells.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Pharmacology
Background:
- Prostaglandin (PG) biosynthesis is a critical cellular process involving phospholipase A2 (PLA2) and cyclooxygenase (COX) enzymes.
- Understanding the functional coupling and regulation of these enzymes is crucial for elucidating inflammatory and signaling pathways.
Purpose of the Study:
- To reconstitute and investigate the functional coupling between distinct PLA2s and COX isozymes in human embryonic kidney 293 cells.
- To characterize the roles of different PLA2 isoforms (cytosolic PLA2, secretory PLA2s, Ca2+-independent PLA2) and COX isozymes (COX-1, COX-2) in immediate and delayed prostaglandin production.
Main Methods:
- Transfection of human embryonic kidney 293 cells with various combinations of PLA2 and COX isoforms.
- Stimulation of cells using calcium ionophore, bradykinin, interleukin-1, and serum to induce immediate and delayed responses.
- Assay of arachidonic acid release and prostaglandin E2 (PGE2) production.
- Inhibition studies using a cPLA2 inhibitor.
- Coculture experiments to assess paracrine signaling.
Main Results:
- Signaling PLA2s (cPLA2, sPLA2-IIA, sPLA2-V) promoted arachidonic acid release and subsequent PGE2 synthesis by both COX-1 and COX-2.
- COX-2 showed a preference for low arachidonic acid concentrations and could activate endogenous arachidonic acid release, unlike COX-1.
- Ca2+-independent PLA2 (iPLA2) preferentially coupled with COX-1 for immediate PGE2 generation.
- Extracellular sPLA2s (sPLA2-IIA, sPLA2-V) augmented PGE2 generation in neighboring COX-expressing cells, indicating a paracrine amplification role.
Conclusions:
- Distinct PLA2 isoforms exhibit differential coupling with COX-1 and COX-2, influencing immediate and delayed prostaglandin biosynthesis.
- Extracellular secretory PLA2s play a significant role as paracrine mediators, amplifying prostaglandin signaling between cells.