Basal cPLA2 phosphorylation is sufficient for Ca2+-induced full activation of cPLA2 in A549 epithelial cells
✍ Scribed by Hui-Chun Wen; Wan-Wan Lin
- Book ID
- 101341479
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 195 KB
- Volume
- 79
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
The release of [ 3 H] arachidonic acid (AA) and its connection with the triggering of the MAP kinase cascade were studied in the human A549 epithelial cell line upon stimulation with thapsigargin. Thapsigargin can increase AA release along with the increase of intracellular calcium concentration, phosphorylation, and activation of extracellular regulated kinase (ERK) and cytosolic phospholipase A 2 (cPLA 2 ). Both ERK and cPLA 2 phosphorylation in response to thapsigargin were inhibited by PD 98059, a specific inhibitor of MAP kinase kinase of the ERK group (MEK), and EGTA. cPLA 2 phosphorylation was not affected by Ro 31-8220 (an inhibitor of all PKC isoforms) or LY 379196 (a PKC selective inhibitor), while both of them indeed attenuated ERK activation. On the other hand, rottlerin (the selective PKC␦ inhibitor), SB 203580 (the selective p38 MAPK inhibitor), and wortmannin (the PI 3-kinase inhibitor) can affect neither cPLA 2 nor ERK phosphorylation. In A549 cells, PKC activator PMA cannot increase either the basal or thapsigargin-induced 3 H-AA release, while it can induce the phosphorylation of ERK and cPLA 2. The PMA-induced ERK phosphorylation was inhibited by Ro 31-8220, LY 379196, rottlerin, and PD 98059, but unaffected by SB 203580 and wortmannin. Moreover, the phosphorylation by PMA was non-additive with that of thapsigargin. This implies that intracellular Ca 2ϩ level is the key factor for induction of cPLA 2 activity and thapsigargin-elicited ERK activation itself is substantially sufficient for cPLA 2 activation upon intracellular Ca 2ϩ increase.