Modifications in FLAP's second cytosolic loop influence 5-LOX interaction, inhibitor binding, and leukotriene formation.

Leukotrienes, synthesized via the 5-lipoxygenase (5-LOX) pathway in the arachidonic acid cascade, are critical in inflammation. Effective leukotriene production requires interaction between 5-LOX and 5-LOX-activating protein (FLAP) at the nuclear membrane. This study used site-directed mutagenesis to explore amino acid residues in FLAP's inhibitor binding pocket and cytosolic loops, assessing their impact on 5-LOX product formation, the FLAP inhibitor MK886's efficacy, 5-LOX translocation, and 5-LOX/FLAP complex formation. Mutations in the second cytosolic loop, especially at residue S108, reduced MK886 potency and disrupted 5-LOX/FLAP complex formation. These results highlight the second cytosolic loop of FLAP in the 5-LOX/FLAP interaction and proper leukotriene formation and suggest that targeting this region could aid in the development of new FLAP inhibitors with improved pharmacokinetics.