Phospholipase A2 (PLA2) enzymes are the upstream regulators of the eicosanoid pathway liberating free arachidonic acid (AA) and other polyunsaturated fatty acids (PUFA).1 The liberation of AA by PLA2 enzymes sets off a cascade of molecular events that involves downstream regulators such as cyclooxygenase (COX) and lipoxygenase (LOX) metabolites leading to inflammation.2 Nonsteroidal anti-inflammatory drugs (NSAIDs) work by inhibiting COX and LOX, but both rely on PLA2 enzymes to provide them with AA. That means PLA2 enzymes can potentially also be targeted to diminish inflammation at an earlier point in the process. Using molecular dynamics (MD) simulations guided by hydrogen/deuterium exchange mass spectrometric (DXMS) experimental data, we have recently elucidated the catalytic cycle of two cellular enzymes, the Group IVA cytosolic (GIVA cPLA2) and Group VIA calcium-independent (GVIA iPLA2) which are the main AA providers in the eicosanoid pathway.3 Our data showed the channels to the active sites of these PLA2s are opened upon allosteric interaction of the enzyme surface with the membrane to facilitate entry of the substrate phospholipid. This constitutes the first detailed study describing the binding and the interaction mechanism of intracellular PLA2s with the membrane bilayer as well as how they bind a single phospholipid molecule in the catalytic site. Similar methods were also employed to understand the binding of various inhibitors to generate structure-activity relationships that facilitate the development of new potent and selective inhibitors for these two enzymes. In fact, we have developed thioether fluoroketone compounds that selectively inhibit GIVA cPLA2 and GVIA iPLA2. These enzymes are implicated in many diseases, and the development of potent and selective inhibitors will aid in the discovery of new therapeutics. References 1. Dennis, E.; Cao, J.; Hsu, Y.-H.; Magrioti, V.; Kokotos, G., Phospholipase A2 enzymes: physical structure, biological function, disease implication, chemical inhibition, and therapeutic intervention. Chem. Rev. 2011, 111, 6130-6185. 2. Dennis, E. A.; Norris, P. C., Eicosanoid storm in infection and inflammation. Nat. Rev. Immunol. 2015, 15, 511-523. 3. Mouchlis, V. D.; Bucher, D.; McCammon, J. A.; Dennis, E. A., Membranes serve as allosteric activators of phospholipase A2, enabling it to extract, bind, and hydrolyze phospholipid substrates. PNAS 2015, 112, E516-E525.

Phospholipases A2: A pharmaceutical target to diminish inflammation

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.