Leukotriene Synthesis in Response to A23187 Is Inhibited by Methyl-β-Cyclodextrin in RBL-2H3 Cells

Leukotrienes (LTs) are produced by several biosynthetic enzymes including cytosolic phospholipase A2 (cPLA2), 5-lipoxygenase (5-LO), and 5-lipoxygenase activating protein (FLAP) in the perinuclear area. In the present study, we showed that pretreatment with methyl-β-cyclodextrin (MβCD), a cholesterol-depleting agent, dramatically reduced the synthesis of LTs in response to A23187 in mast cells. A23187-induced LT synthesis was inhibited by pretreatment with MβCD, and this effect was reversed when cholesterol was added. In an approach to identifying the MβCD-sensitive protein(s), we observed that FLAP co-localized with flotillin-1, a lipid raft marker protein, in the lipid raft-rich low-density region of sucrose gradients. In addition, electron microscopic analysis revealed that FLAP co-localized with flotillin-1. Together, these results suggest that FLAP is present in cholesterol-rich lipid raft-like domains and that its localization in these domains is critical for LT synthesis.