The mechanism of stimulation of the inactive 5-lipoxygenase in mast/basophil PT-18 cells by μM 15-hydroxyeicosatetraenoic acid (15-HETE) was investigated. Treatment of PT-18 cells with pM 15-[3H]HETE at 4 ° for 3 h resulted in the cell association of 10% of the ligand: two-thirds was incorporated into cellular lipids and a third was bound to specific 15-HETE cellular binding sites. Binding data analysis indicated a single class of 15- HETE binding sites with a K(d) of 162 nM and a B(max) of 7.1 x 105 sites/cell. Unlabeled 15-HETE, 12-HETE, and 5,15-diHETE inhibited the binding of 15-[3H]HETE to cells, whereas LTB4 and PGF(2α) were relatively ineffective. 2.4 μM 15-HETE (unlabeled) prevented 50% 15-[3H]HETE incorporation. Examination of the effects of 15-HETE methyl ester, 12-HETE, 5,15-diHETE, and pertussis toxin on both the 15-HETE-induced 5-lipoxygenase activation and 15-HETE cell association processes indicated a preponderant correlation of this activation process with specific 15-HETE binding rather than 15-HETE incorporation into phospholipids. In addition, 5,15-diHETE itself stimulated the inactive 5-lipoxygenase and eight times more [3H]diHETE was bound to cells than became incorporated into cellular lipids. The results support the involvement of low affinity 15-HETE receptors, rather than 15-HETE incorporation into cellular lipids, in the 15-HETE-induced stimulation of the 5-lipoxygenase in PT-18 cells.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|State||Published - Dec 1 1992|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology