Activation of Mitochondrial Calcium-independent Phospholipase A(2)gamma (iPLA(2)gamma) by Divalent Cations Mediating Arachidonate Release and Production of Downstream Eicosanoids

作者：Moon Sung Ho; Jenkins Christopher M; Liu Xinping; Guan Shaoping; Mancuso David J; Gross Richard W^*

来源：JOURNAL OF BIOLOGICAL CHEMISTRY, 2012, 287(18): 14880-14895.

DOI：10.1074/jbc.M111.336776

Calcium-independent phospholipase A(2)gamma (iPLA(2)gamma) (PNPLA8) is the predominant phospholipase activity in mammalian mitochondria. However, the chemical mechanisms that regulate its activity are unknown. Here, we utilize iPLA(2)gamma gain of function and loss of function genetic models to demonstrate the robust activation of iPLA(2)gamma in murine myocardial mitochondria by Ca2+ or Mg2+ ions. Calcium ion stimulated the production of 2-arachidonoyl-lysophosphatidylcholine (2-AA-LPC) from 1-palmitoyl-2-[14C] arachidonoyl- sn-glycero-3-phosphocholine during incubations with wild-type heart mitochondrial homogenates. Furthermore, incubation of mitochondrial homogenates from transgenic myocardium expressing iPLA(2)gamma resulted in 13- and 25-fold increases in the initial rate of radiolabeled 2-AA-LPC and arachidonic acid (AA) production, respectively, in the presence of calcium ion. Mass spectrometric analysis of the products of calcium-activated hydrolysis of endogenous mitochondrial phospholipids in transgenic iPLA(2)gamma mitochondria revealed the robust production of AA, 2-AA-LPC, and 2-docosahexaenoyl-LPC that was over 10-fold greater than wild-type mitochondria. The mechanism- based inhibitor (R)-(E)-6-(bromomethylene)-3-(1-naphthalenyl)- 2H-tetrahydropyran-2-one (BEL) (iPLA(2)gamma selective), but not its enantiomer, (S)-BEL (iPLA(2)gamma selective) or pyrrolidine (cytosolic PLA(2)gamma selective), markedly attenuated Ca2+ -dependent fatty acid release and polyunsaturated LPC production. Moreover, Ca2+-induced iPLA(2)gamma activation was accompanied by the production of downstream eicosanoid metabolites that were nearly completely ablated by (R)-BEL or by genetic ablation of iPLA(2)gamma. Intriguingly, Ca2+ -induced iPLA(2)gamma activation was completely inhibited by long-chain acyl-CoA (IC50 similar to 20 mu M) as well as by a nonhydrolyzable acyl-CoA thioether analog. Collectively, these results demonstrate that mitochondrial iPLA(2)gamma is activated by divalent cations and inhibited by acyl-CoA modulating the generation of biologically active metabolites that regulate mitochondrial bioenergetic and signaling functions.

• 出版日期2012-4-27