Membrane-dependent Activities of Human 15-LOX-2 and Its Murine Counterpart

• Published in: The Journal of biological chemistry 2016-09, Vol.291 (37), p.19413-19424
• Main Authors: Bender, Gunes, Schexnaydre, Erin E., Murphy, Robert C., Uhlson, Charis, Newcomer, Marcia E.
• Format: Article
• Language: English
• Subjects: arachidonic acid (AA) (ARA); eicosanoid; lipid signaling; lipoxygenase pathway; phospholipid
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M116.741454

The enzyme encoded by the ALOX15B gene has been linked to the development of atherosclerotic plaques in humans and in a mouse model of hypercholesterolemia. In vitro, these enzymes, which share 78% sequence identity, generate distinct products from their substrate arachidonic acid: the human enzyme, a 15-S-hydroperoxy product; and the murine enzyme, an 8-S-product. We probed the activities of these enzymes with nanodiscs as membrane mimics to determine whether they can access substrate esterified in a bilayer and characterized their activities at the membrane interface. We observed that both enzymes transform phospholipid-esterified arachidonic acid to a 15-S-product. Moreover, when expressed in transfected HEK cells, both enzymes result in significant increases in the amounts of 15-hydroxyderivatives of eicosanoids detected. In addition, we show that 15-LOX-2 is distributed at the plasma membrane when the HEK293 cells are stimulated by the addition Ca2+ ionophore and that cellular localization is dependent upon the presence of a putative membrane insertion loop. We also report that sequence differences between the human and mouse enzymes in this loop appear to confer distinct mechanisms of enzyme-membrane interaction for the homologues.