Membrane-dependent Activities of Human 15-LOX-2 and Its Murine Counterpart: IMPLICATIONS FOR MURINE MODELS OF ATHEROSCLEROSIS

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 CA(2+) 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.

arachidonic acid (AA) (ARA); eicosanoid; lipid signaling; lipoxygenase pathway; phospholipid.