Governing Mechanism of Phospholipids Peroxidation via 15-Lipoxygenase, A Key Player in Ferroptosis Cell Death Pathway

Ferroptosis is a newly discovered cell death pathway that is characterized by the production of lipid hydroperoxides. Although the exact lipid peroxidation pathways have not been identified, recent findings indicate the involvement of lipoxygenases (LOXs), particularly, 15LOX acting directly —independently from phospholipases— on the membrane. Here, a combination of computational approaches was used to study interactions of human 15LOX-2 with a membrane, and to identify preferred phospholipid substrates for this enzyme. Using molecular docking modeling, the binding poses and the binding affinities of various esterified lipids and arachidonic acid —a known substrate of LOXs—were compared. It has been shown that ferroptosis-triggering events occur predominantly in the endoplasmic reticulum. Therefore, coarse-grained molecular dynamics (CGMD) simulations were applied to study the interactions of 15LOX-2 with an endoplasmic reticulum membrane mimic. Our modeling data revealed that phosphatidylethanolamine and phosphatidylinositol are the most likely membrane substrates for 15LOX-2. CGMD simulations (2 μs runs) confirmed that the amino-terminal β-barrel domain (called PLAT) of 15LOX-2 is responsible for membrane binding. This domain entered deeply into the membrane. To establish the positioning of the catalytic site's opening and its orientation with respect to the membrane surface, we reconstructed an atomistic model based on the CGMD data. The opening of the J-shaped catalytic site invariably oriented itself toward the membrane surface facilitating phospholipid hydroperoxidation. Accordingly, we propose a model indicating that the PLAT domain strongly entangles 15-LOX in the membrane providing accessibility of the active site to esterified lipids embedded in the membrane. These data have been supported by grants P01HL114453, U19AI068021 and HFSP-RGP0013/2014.