Characterization of FKGK18 as inhibitor of group VIA Ca2+-independent phospholipase A2 (iPLA2?): candidate drug for preventing beta-cell apoptosis and diabetes.

ABSTRACT: Ongoing studies suggest an important role for iPLA2? in a multitude of biological processes and it has been implicated in neurodegenerative, skeletal and vascular smooth muscle disorders, bone formation, and cardiac arrhythmias. Thus, identifying an iPLA2?inhibitor that can be reliably and safely used in vivo is warranted. Currently, the mechanism-based inhibitor bromoenol lactone (BEL) is the most widely used to discern the role of iPLA2? in biological processes. While BEL is recognized as a more potent inhibitor of iPLA2 than of cPLA2 or sPLA2, leading to its designation as a "specific" inhibitor of iPLA2, it has been shown to also inhibit non-PLA2 enzymes. A potential complication of its use is that while the S and R enantiomers of BEL exhibit preference for cytosol-associated iPLA2? and membrane-associated iPLA2?, respectively, the selectivity is only 10-fold for both. In addition, BEL is unstable in solution, promotes irreversible inhibition, and may be cytotoxic, making BEL not amenable for in vivo use. Recently, a fluoroketone (FK)-based compound (FKGK18) was described as a potent inhibitor of iPLA2?. Here we characterized its inhibitory profile in beta-cells and find that FKGK18: (a) inhibits iPLA2? with a greater potency (100-fold) than iPLA2?, (b) inhibition of iPLA2? is reversible, (c) is an ineffective inhibitor of ?-chymotrypsin, and (d) inhibits previously described outcomes of iPLA2? activation including (i) glucose-stimulated insulin secretion, (ii) arachidonic acid hydrolysis; as reflected by PGE2 release from human islets, (iii) ER stress-induced neutral sphingomyelinase 2 expression, and (iv) ER stress-induced beta-cell apoptosis. These findings suggest that FKGK18 is similar to BEL in its ability to inhibit iPLA2?. Because, in contrast to BEL, it is reversible and not a non-specific inhibitor of proteases, it is suggested that FKGK18 is more ideal for ex vivo and in vivo assessments of iPLA2? role in biological functions.

SUBMITTER: Ali T 

PROVIDER: S-EPMC3748103 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature