5-Lipoxygenase-activating protein homodimer in human neutrophils: evidence for a role in leukotriene biosynthesis.
FLAP (5-lipoxygenase-activating protein) is a nuclear transmembrane protein involved in the biosynthesis of LTs (leukotrienes) and other 5-LO (5-lipoxygenase) products. However, little is known about its mechanism of action. In the present study, using cross-linkers, we demonstrate that FLAP is present as a monomer and a homodimer in human PMN (polymorphonuclear cells). The functional relevance of the FLAP dimer in LT biosynthesis was assessed in different experimental settings. First, the 5-LO substrate AA (arachidonic acid) concomitantly disrupted the FLAP dimer (at > or =10 microM) and inhibited LT biosynthesis. Secondly, using Sf9 cells expressing active and inactive FLAP mutants and 5-LO, we observed that the FLAP mutants capable of supporting 5-LO product biosynthesis also form the FLAP dimer, whereas inactive FLAP mutants do not. Finally, we showed that FLAP inhibitors such as MK-0591 which block LT biosynthesis in human PMN, disrupt the FLAP dimer in PMN membranes with a similar IC50. The present study demonstrates that LT biosynthesis in intact cells not only requires the presence of FLAP but its further organization into a FLAP homodimer.
Plante
Hendrick
H
Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ and Faculté de Médecine, Université Laval, 2705 Boulevard Laurier, Quebec, G1V 4G2, Canada.
Picard
Serge
S
Mancini
Joseph
J
Borgeat
Pierre
P
D058927:5-Lipoxygenase-Activating Proteins; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D002460:Cell Line; D019281:Dimerization; D006801:Humans; D015289:Leukotrienes / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D009504:Neutrophils / Q000378:metabolism*
D058927:5-Lipoxygenase-Activating Proteins; C548592:ALOX5AP protein, human; D002352:Carrier Proteins; D015289:Leukotrienes; D008565:Membrane Proteins; D016718:Arachidonic Acid